2016 Vol. 33, No. 5
Effects of preform structure on thermal conductivity of needle-punched quartz fiber/epoxy composites
2016, 33(5): 955-961.
doi: 10.13801/j.cnki.fhclxb.20151217.001
Abstract:
In order to investigate the effects of preform structure on thermal conductivity of needle-punched quartz fiber/epoxy composites, the needle-punched quartz fiber/epoxy composites were prepared by needle-punching step by step and resin transfer molding process. The thermal conductivities of epoxy and needle-punched quartz fiber/epoxy composites with different preform structures were measured by using transient hot-wire method. Results show that the thermal conductivities of needle-punched quartz fiber/epoxy composites increase with the increase of fiber volume fraction. Compared with epoxy, the thermal conductivity of short-cut quartz fiber web reinforced epoxy increases by 35.9%. When hot-wire is parallel to the direction of fibers in the non-woven cloth of needle-punched quartz fiber/epoxy composites, the thermal conductivities of two needle-punched quartz fiber/epoxy composites, which are reinforced by short-cut quartz fiber web and non-woven quartz fiber cloth, increase by 45.5% and 46.4%, respectively. When hot-wire is perpendicular to the direction of fibers in non-woven cloth, the increase of thermal conductivities are 56.4% and 61.8%, respectively. The thermal conductivity of needle-punched quartz fiber/epoxy composites would be affected not only by the quartz fiber volume fraction, but also the volume fraction and orientation of the fiber in the non-woven cloth of preform.
In order to investigate the effects of preform structure on thermal conductivity of needle-punched quartz fiber/epoxy composites, the needle-punched quartz fiber/epoxy composites were prepared by needle-punching step by step and resin transfer molding process. The thermal conductivities of epoxy and needle-punched quartz fiber/epoxy composites with different preform structures were measured by using transient hot-wire method. Results show that the thermal conductivities of needle-punched quartz fiber/epoxy composites increase with the increase of fiber volume fraction. Compared with epoxy, the thermal conductivity of short-cut quartz fiber web reinforced epoxy increases by 35.9%. When hot-wire is parallel to the direction of fibers in the non-woven cloth of needle-punched quartz fiber/epoxy composites, the thermal conductivities of two needle-punched quartz fiber/epoxy composites, which are reinforced by short-cut quartz fiber web and non-woven quartz fiber cloth, increase by 45.5% and 46.4%, respectively. When hot-wire is perpendicular to the direction of fibers in non-woven cloth, the increase of thermal conductivities are 56.4% and 61.8%, respectively. The thermal conductivity of needle-punched quartz fiber/epoxy composites would be affected not only by the quartz fiber volume fraction, but also the volume fraction and orientation of the fiber in the non-woven cloth of preform.
2016, 33(5): 962-969.
doi: 10.13801/j.cnki.fhclxb.20151126.001
Abstract:
Polyborosilazane with ethynyl group (PBSZ) was synthesized and hybrided with poly(silicon-containing arylacetylene) (PSA) resin to improve thermal-oxidation resistance of polyarylacetylene resin. The structure of PBSZ was characterized by FTIR, NMR and gel permeation chromatography (GPC). The processing properties of PBSZ/PSA resin were investigated by rotational rheometer and DSC, and the thermostability and thermal-oxidation resistance of PBSZ/PSA resin were examined by TGA, SEM and EDS. The results show that PBSZ/PSA resin offers good processability, and could be cured at 210℃ with low exothermal heat. The cured resin residual yields up to 38.0% at 1000℃ under air, and a dense protective layer about 60-80 μm thickness is formed after being oxidized, which inhibits the materials from being oxidized by oxygen. Besides, the sinter of cured resin by 1200℃ also has thermal-oxidation resistance, and a dense ceramic protective layer about 10 μm thickness is produced after being oxidized at 1200℃ and effectively keeps the materials from being oxidized by oxygen.
Polyborosilazane with ethynyl group (PBSZ) was synthesized and hybrided with poly(silicon-containing arylacetylene) (PSA) resin to improve thermal-oxidation resistance of polyarylacetylene resin. The structure of PBSZ was characterized by FTIR, NMR and gel permeation chromatography (GPC). The processing properties of PBSZ/PSA resin were investigated by rotational rheometer and DSC, and the thermostability and thermal-oxidation resistance of PBSZ/PSA resin were examined by TGA, SEM and EDS. The results show that PBSZ/PSA resin offers good processability, and could be cured at 210℃ with low exothermal heat. The cured resin residual yields up to 38.0% at 1000℃ under air, and a dense protective layer about 60-80 μm thickness is formed after being oxidized, which inhibits the materials from being oxidized by oxygen. Besides, the sinter of cured resin by 1200℃ also has thermal-oxidation resistance, and a dense ceramic protective layer about 10 μm thickness is produced after being oxidized at 1200℃ and effectively keeps the materials from being oxidized by oxygen.
2016, 33(5): 970-975.
doi: 10.13801/j.cnki.fhclxb.20160107.001
Abstract:
The diglycidyl ether of 1, 3-bis (4-hydroxyphenyl)adamantane(DGEBAD) with low molecular weight was synthesized from 1, 3-bis (4-hydroxyphenyl) adamantane (BHPA) and epichlorohydrin (ECH) by two-step method. The structure and molecular weight were confirmed by FTIR, 1H-NMR and gel permeation chromatography(GPC), and epoxy value was obtained by titration. The rheology property was also characterized by rotational rheometer. DGEBAD was cured with 4, 4'-diaminodiphenyl methane (DDM). The mechanical properties, water absorption rate and heat resistance characteristics of the cured DGEBAD-DDM resin system were investigated. The tensile strength and the glass transition temperature of the cured DGEBAD-DDM resin system is 90 MPa and 163℃, respectively and 5% mass loss temperature occurs at up to 401℃. The water absorption rate of the cured DGEBAD-DDM decreases by 31.60% compared to the cured epoxy resin E51-DDM.
The diglycidyl ether of 1, 3-bis (4-hydroxyphenyl)adamantane(DGEBAD) with low molecular weight was synthesized from 1, 3-bis (4-hydroxyphenyl) adamantane (BHPA) and epichlorohydrin (ECH) by two-step method. The structure and molecular weight were confirmed by FTIR, 1H-NMR and gel permeation chromatography(GPC), and epoxy value was obtained by titration. The rheology property was also characterized by rotational rheometer. DGEBAD was cured with 4, 4'-diaminodiphenyl methane (DDM). The mechanical properties, water absorption rate and heat resistance characteristics of the cured DGEBAD-DDM resin system were investigated. The tensile strength and the glass transition temperature of the cured DGEBAD-DDM resin system is 90 MPa and 163℃, respectively and 5% mass loss temperature occurs at up to 401℃. The water absorption rate of the cured DGEBAD-DDM decreases by 31.60% compared to the cured epoxy resin E51-DDM.
2016, 33(5): 976-983.
doi: 10.13801/j.cnki.fhclxb.20151223.003
Abstract:
Three kinds of elastomers, polyolefin elastomer (POE), elastomer modified polyethylene (BPB) and graft modified polyolefin elastomer (A669) were introduced to preparation process of wood flour/high density polyethylene (WF/HDPE) composite to improve the toughness of wood-plastic composites. The kinds and contents of toughening agent at which can simultaneously improve the toughness and maintain the rigidity of WF/HDPE composites were determined by the impact strength and flexural elastic modulus test of WF/HDPE composites. The toughening principles were analyzed by the aid of the crystallization behavior, thermal dynamic property and interface bonding analysis. Through comparison, it shows that A669 is the most effective one; when adding mass fraction is 4%, the impact strength is 15.31 kJ/m2, increases by 52.34% comparing to the composite without A669, while the flexural elastic modulus just decreases by 6.09%. XRD and DSC analysis results show that, adding A669 hinders the crystallization behavior of WF/HDPE composites, which decreases the crystallization temperature and the crystallinity, while increases the grain size and the size of the diffraction surface corresponding to the diffraction angle. Thus more energy is absorbed and lost, and the glass transition temperature of WF/HDPE composite decreases. The DMA and SEM analysis results show that, the WF/HDPE composites with A669 present more viscosity characteristic, and the wiredrawing phenomenon of plastic matrix appears on the fracture surface, improving the toughness of the material. The torque rheometer test shows that, the balance torque of WF/HDPE composites does not change significantly, which indicates that A669 will not adversely affect the processing. Therefore, A669 can provide wood-plastic composite with both good toughness and stiffness under an appropriate use level. The results of present study will greatly promote the application of wood-plastic composite in building templates etc.
Three kinds of elastomers, polyolefin elastomer (POE), elastomer modified polyethylene (BPB) and graft modified polyolefin elastomer (A669) were introduced to preparation process of wood flour/high density polyethylene (WF/HDPE) composite to improve the toughness of wood-plastic composites. The kinds and contents of toughening agent at which can simultaneously improve the toughness and maintain the rigidity of WF/HDPE composites were determined by the impact strength and flexural elastic modulus test of WF/HDPE composites. The toughening principles were analyzed by the aid of the crystallization behavior, thermal dynamic property and interface bonding analysis. Through comparison, it shows that A669 is the most effective one; when adding mass fraction is 4%, the impact strength is 15.31 kJ/m2, increases by 52.34% comparing to the composite without A669, while the flexural elastic modulus just decreases by 6.09%. XRD and DSC analysis results show that, adding A669 hinders the crystallization behavior of WF/HDPE composites, which decreases the crystallization temperature and the crystallinity, while increases the grain size and the size of the diffraction surface corresponding to the diffraction angle. Thus more energy is absorbed and lost, and the glass transition temperature of WF/HDPE composite decreases. The DMA and SEM analysis results show that, the WF/HDPE composites with A669 present more viscosity characteristic, and the wiredrawing phenomenon of plastic matrix appears on the fracture surface, improving the toughness of the material. The torque rheometer test shows that, the balance torque of WF/HDPE composites does not change significantly, which indicates that A669 will not adversely affect the processing. Therefore, A669 can provide wood-plastic composite with both good toughness and stiffness under an appropriate use level. The results of present study will greatly promote the application of wood-plastic composite in building templates etc.
2016, 33(5): 984-990.
doi: 10.13801/j.cnki.fhclxb.20160121.002
Abstract:
In order to investigate the ablation mechanisms of carbon/phenolic composites which were used in thermal protection system of hypersonic vehicles with blunt shapes, the mathematical model for ablation behavior was established firstly, the model took a variety of energy dissipation mechanisms, including the thermal radiation of material surface, the heat absorption of the solid phase by temperature rise, the heat absorption of matrix pyrolysis reaction, the ejection of high temperature pyrolysis gas, "heat block" effect caused by mass ejection, temperature rise and heat absorption by expansion of pyrolysis gas etc., into account, and the solving of mathematical model was realized by finite element method. Then, the ablation behaviors of carbon/phenolic composites under aerodynamic heating environment that cold wall heat flux was 400 kW·m-2 and enthalpy was 5 MJ·kg-1 were forecasted. The results show that during heating period, the depth of carbonized layer in carbon/phenolic composite whose thickness is 20 mm increases continually, the surface temperature reaches 1420 K and the rear wall temperature is 346 K at 100 s, the pyrolysis gas pressure arrives 10.3 atm and the depth of carbonized layer is 7.50 mm. The conclusions obtained can provide supports for the design of thermal protection system in hypersonic vehicles which have long-time and large area thermal protection requirements.
In order to investigate the ablation mechanisms of carbon/phenolic composites which were used in thermal protection system of hypersonic vehicles with blunt shapes, the mathematical model for ablation behavior was established firstly, the model took a variety of energy dissipation mechanisms, including the thermal radiation of material surface, the heat absorption of the solid phase by temperature rise, the heat absorption of matrix pyrolysis reaction, the ejection of high temperature pyrolysis gas, "heat block" effect caused by mass ejection, temperature rise and heat absorption by expansion of pyrolysis gas etc., into account, and the solving of mathematical model was realized by finite element method. Then, the ablation behaviors of carbon/phenolic composites under aerodynamic heating environment that cold wall heat flux was 400 kW·m-2 and enthalpy was 5 MJ·kg-1 were forecasted. The results show that during heating period, the depth of carbonized layer in carbon/phenolic composite whose thickness is 20 mm increases continually, the surface temperature reaches 1420 K and the rear wall temperature is 346 K at 100 s, the pyrolysis gas pressure arrives 10.3 atm and the depth of carbonized layer is 7.50 mm. The conclusions obtained can provide supports for the design of thermal protection system in hypersonic vehicles which have long-time and large area thermal protection requirements.
2016, 33(5): 991-997.
doi: 10.13801/j.cnki.fhclxb.20160121.001
Abstract:
In order to investigate the buckling, postbuckling characteristics and load capacity of composite sandwich beam under the effect of axial compression, test investigation and finite element simulation were carried out. Firstly, a series of buckling characteristic tests of composite sandwich beams were conducted. The effects of ply ratio angle, length of beam, face layer thickness and core layer thickness on buckling, postbuckling failure modes and ultimate load were discussed. Then, based on the nonlinear buckling theory, 3D cohesive interface elements were used to simulate the debond between skin and core, and initial predeformation as well as material damage criteria were also introduced to simulate and investigate the buckling characteristics and ultimate load of composite sandwich beam under axial compression. The results show that interface debond is the important mode of buckling failure. Comparing the ultimate load calculated by simulation with the test results, the errors are controlled within 10%. The conclusions obtained prove that the method can predict the postbuckling path, failure mode and ultimate load accurately.
In order to investigate the buckling, postbuckling characteristics and load capacity of composite sandwich beam under the effect of axial compression, test investigation and finite element simulation were carried out. Firstly, a series of buckling characteristic tests of composite sandwich beams were conducted. The effects of ply ratio angle, length of beam, face layer thickness and core layer thickness on buckling, postbuckling failure modes and ultimate load were discussed. Then, based on the nonlinear buckling theory, 3D cohesive interface elements were used to simulate the debond between skin and core, and initial predeformation as well as material damage criteria were also introduced to simulate and investigate the buckling characteristics and ultimate load of composite sandwich beam under axial compression. The results show that interface debond is the important mode of buckling failure. Comparing the ultimate load calculated by simulation with the test results, the errors are controlled within 10%. The conclusions obtained prove that the method can predict the postbuckling path, failure mode and ultimate load accurately.
2016, 33(5): 998-1008.
doi: 10.13801/j.cnki.fhclxb.20160112.004
Abstract:
The glass fiber reinforced plastic (GFRP)-concrete composite beam consists of a concrete slab on the upper side, a GFRP profile on the lower side and shear connectors to connect these two sides. A test study was conducted on the behaviors of two GFRP-concrete composite beams (non-prestressed and external prestressed composite beams each had one) under sustained load for one year. A time-dependent finite element parametric analysis of 24 GFRP-concrete composite beams, taking coupling effect of the shrinkage and creep of concrete and creep of GFRP profile into account, was carried out for 50 years. The results show that long-term deflections of the non-prestressed and external prestressed composite beams are 1.42 and 2.91 times of their respective instantaneous deflections under sustained load for one year. The long-term slips of the non-prestressed and external prestressed composite beams are 0.230 mm and 0.164 mm, respectively. Compared with initial slips, the terminal slips of the two composite beams increase by 53.3% and 58.2%, respectively. The ratios of long-term deflection to the instantaneous deflection for the non-prestressed composite beam are between 1.50-1.56 while the ratios of the long-term deflection to the instantaneous deflection for the external prestressed composite beam are between 3.03-6.08. Based on the above researches, calculation proposals of long-term deflections of GFRP-concrete composite beams were proposed.
The glass fiber reinforced plastic (GFRP)-concrete composite beam consists of a concrete slab on the upper side, a GFRP profile on the lower side and shear connectors to connect these two sides. A test study was conducted on the behaviors of two GFRP-concrete composite beams (non-prestressed and external prestressed composite beams each had one) under sustained load for one year. A time-dependent finite element parametric analysis of 24 GFRP-concrete composite beams, taking coupling effect of the shrinkage and creep of concrete and creep of GFRP profile into account, was carried out for 50 years. The results show that long-term deflections of the non-prestressed and external prestressed composite beams are 1.42 and 2.91 times of their respective instantaneous deflections under sustained load for one year. The long-term slips of the non-prestressed and external prestressed composite beams are 0.230 mm and 0.164 mm, respectively. Compared with initial slips, the terminal slips of the two composite beams increase by 53.3% and 58.2%, respectively. The ratios of long-term deflection to the instantaneous deflection for the non-prestressed composite beam are between 1.50-1.56 while the ratios of the long-term deflection to the instantaneous deflection for the external prestressed composite beam are between 3.03-6.08. Based on the above researches, calculation proposals of long-term deflections of GFRP-concrete composite beams were proposed.
2016, 33(5): 1009-1019.
doi: 10.13801/j.cnki.fhclxb.20160118.005
Abstract:
Based on the tensile strength tests of 12 groups of 72 pieces of sprayed fiber reinforced polymer (FRP) specimens, the effects of factors such as fiber type, resin matrix material, fibers volume fraction, hybrid ratio of fibers and fiber length etc. on the properties such as tensile strength, elastic modulus and elongation at break etc. of sprayed FRP were investigated. The seismic performance of earthquake damaged reinforced concrete (RC) columns specimens strengthened with sprayed basalt fiber reinforced polymer (BFRP) and hybrid basalt-carbon fiber reinforced polymer (BF-CFRP) was investigated by the quasi-static test of 8 RC columns, and the influences of the thickness of sprayed FRP layer, hybrid ratio of fibers, pre-damage degree of columns and the axial compression ratio of column etc. on the ultimate load capacity, lateral deformation resistance, degradation characteristics of stiffness and hysteresis properties of the strengthened specimens were analyzed. The test results show that the cooperative working performance of glass fiber and vinylester matrix is the best, and basalt fiber can be used as a favorable succedaneum of glass fiber because of its excellent performance of high durability, good ductility and good cooperative working performance with vinylester matrix; hybrid basalt fibers with small amount of carbon fibers used as reinforcement for resin matrix can effectively increase the tensile strength and deformation performance of sprayed FRP; earthquake damaged RC column can almost be rehabilitated to its designed ultimate load capacity before the earthquake damage by strengthening with sprayed FRP, and both the ductility and the ability of energy dissipation can be effectively enhanced. This strengthening technique can fast strengthen the earthquake damaged RC column in seismic area and effectively hinder the collapse of whole structures exposed to the aftershock and other heavy damages.
Based on the tensile strength tests of 12 groups of 72 pieces of sprayed fiber reinforced polymer (FRP) specimens, the effects of factors such as fiber type, resin matrix material, fibers volume fraction, hybrid ratio of fibers and fiber length etc. on the properties such as tensile strength, elastic modulus and elongation at break etc. of sprayed FRP were investigated. The seismic performance of earthquake damaged reinforced concrete (RC) columns specimens strengthened with sprayed basalt fiber reinforced polymer (BFRP) and hybrid basalt-carbon fiber reinforced polymer (BF-CFRP) was investigated by the quasi-static test of 8 RC columns, and the influences of the thickness of sprayed FRP layer, hybrid ratio of fibers, pre-damage degree of columns and the axial compression ratio of column etc. on the ultimate load capacity, lateral deformation resistance, degradation characteristics of stiffness and hysteresis properties of the strengthened specimens were analyzed. The test results show that the cooperative working performance of glass fiber and vinylester matrix is the best, and basalt fiber can be used as a favorable succedaneum of glass fiber because of its excellent performance of high durability, good ductility and good cooperative working performance with vinylester matrix; hybrid basalt fibers with small amount of carbon fibers used as reinforcement for resin matrix can effectively increase the tensile strength and deformation performance of sprayed FRP; earthquake damaged RC column can almost be rehabilitated to its designed ultimate load capacity before the earthquake damage by strengthening with sprayed FRP, and both the ductility and the ability of energy dissipation can be effectively enhanced. This strengthening technique can fast strengthen the earthquake damaged RC column in seismic area and effectively hinder the collapse of whole structures exposed to the aftershock and other heavy damages.
2016, 33(5): 1020-1025.
doi: 10.13801/j.cnki.fhclxb.20151225.004
Abstract:
Stent is a very important part of spacecraft final assembly, which is founded by metal with heavy mass and low success. High dimension stability of stent is required urgently within intricate space environment. In order to improve the structural stiffness and abate the mass, a representative stent was selected to perform lightweight research. Based on the performance parameters of carbon fiber composite and boundary conditions, the finite element model was established and simulation analysis was performed firstly. Then the manufacture technology of composite stent was created and a composite stent was achieved. Finally, the testing scheme was made. The mechanical property comparison with metal and carbon fiber composite stent was worked out by evaluating the response of sine and random vibration. The result indicates that carbon fiber composite stent behaves better mechanical performance with lighter mass.
Stent is a very important part of spacecraft final assembly, which is founded by metal with heavy mass and low success. High dimension stability of stent is required urgently within intricate space environment. In order to improve the structural stiffness and abate the mass, a representative stent was selected to perform lightweight research. Based on the performance parameters of carbon fiber composite and boundary conditions, the finite element model was established and simulation analysis was performed firstly. Then the manufacture technology of composite stent was created and a composite stent was achieved. Finally, the testing scheme was made. The mechanical property comparison with metal and carbon fiber composite stent was worked out by evaluating the response of sine and random vibration. The result indicates that carbon fiber composite stent behaves better mechanical performance with lighter mass.
Simulation on damage in quasi-isotropic fiber-reinforced composite laminates under open-hole tension
2016, 33(5): 1026-1032.
doi: 10.13801/j.cnki.fhclxb.20160112.005
Abstract:
A new 3D finite element model was established, which had been used to simulate the open-hole tensile damage of quasi-isotropic fiber-reinforced composite laminates with stacking sequences of [45/0/-45/90]s and [45/-45/90/0]s. Each ply was modeled by 3D solid elements (C3D8R in ABAQUS notation). Because the matrix constituent is much weaker than the fiber, longitudinal splitting or matrix cracking may take place at a very low tensile load due to the local shear force near the hole edge. The longitudinal splitting can blunt the hole and alleviate the stress concentration. And the load-carrying capacity of the material will be enhanced. In order to accurately simulate the damage of the laminates, two surface-based cohesive contacts had been inserted tangential to the hole along the fiber direction in each ply (except for the 90° ply) to simulate the intra-ply longitudinal splitting. Meanwhile, surfaced-based cohesive contacts had also been used to simulate the inter-ply delamination characteristic. In order to improve the computation efficiency and guarantee the calculation accuracy, fine mesh had been used within the region around the hole and relative coarse mesh in other regions. Within the cohesive zone, a certain number of elements was ensured, so that we can both accurately capture the stress distribution and alleviate the mesh dependency. When compared with experimental data in published literature, a good agreement is achieved.
A new 3D finite element model was established, which had been used to simulate the open-hole tensile damage of quasi-isotropic fiber-reinforced composite laminates with stacking sequences of [45/0/-45/90]s and [45/-45/90/0]s. Each ply was modeled by 3D solid elements (C3D8R in ABAQUS notation). Because the matrix constituent is much weaker than the fiber, longitudinal splitting or matrix cracking may take place at a very low tensile load due to the local shear force near the hole edge. The longitudinal splitting can blunt the hole and alleviate the stress concentration. And the load-carrying capacity of the material will be enhanced. In order to accurately simulate the damage of the laminates, two surface-based cohesive contacts had been inserted tangential to the hole along the fiber direction in each ply (except for the 90° ply) to simulate the intra-ply longitudinal splitting. Meanwhile, surfaced-based cohesive contacts had also been used to simulate the inter-ply delamination characteristic. In order to improve the computation efficiency and guarantee the calculation accuracy, fine mesh had been used within the region around the hole and relative coarse mesh in other regions. Within the cohesive zone, a certain number of elements was ensured, so that we can both accurately capture the stress distribution and alleviate the mesh dependency. When compared with experimental data in published literature, a good agreement is achieved.
2016, 33(5): 1033-1039.
doi: 10.13801/j.cnki.fhclxb.20160120.003
Abstract:
In order to satisfy the requirement of efficiency and reliability for prepreg change bonding during composite automatic placement and winding process, based on rheology theory and Gutowski analytical method of layup, hot-press bonding model was established firstly. Then, the control equation of resin fluid under parallel plate squeezing was established by power law model. Finally, the relationship between bonding strength and bonding pressure, resin viscosity, bonding temperature, bonding time (or bonding velocity) as well as bonding length in static bonding state and dynamic bonding state were analyzed, and static and dynamic hot-press bonding mechanisms were designed. The results show that the bonding strength of prepreg increases with the increase of bonding pressure, bonding temperature, bonding time and bonding length. The conclusions obtained can help to design the bonding mechanism which satisfies the requirements for fast, stable and reliable etc., and lay the theoretical and designing foundations for the development of prepreg rapid hot-press bonding system.
In order to satisfy the requirement of efficiency and reliability for prepreg change bonding during composite automatic placement and winding process, based on rheology theory and Gutowski analytical method of layup, hot-press bonding model was established firstly. Then, the control equation of resin fluid under parallel plate squeezing was established by power law model. Finally, the relationship between bonding strength and bonding pressure, resin viscosity, bonding temperature, bonding time (or bonding velocity) as well as bonding length in static bonding state and dynamic bonding state were analyzed, and static and dynamic hot-press bonding mechanisms were designed. The results show that the bonding strength of prepreg increases with the increase of bonding pressure, bonding temperature, bonding time and bonding length. The conclusions obtained can help to design the bonding mechanism which satisfies the requirements for fast, stable and reliable etc., and lay the theoretical and designing foundations for the development of prepreg rapid hot-press bonding system.
2016, 33(5): 1040-1047.
doi: 10.13801/j.cnki.fhclxb.20160120.002
Abstract:
In order to reduce the test cost for obtaining the design allowables of composites, a regression analysis-based B-basis value statistical method merging multiple condition samples which was latest issued by Composite Material Handbook-17-G was introduced, and the rationality and applicable conditions for the addition of engineering experience judgment in the check of variation between batches, the equality check for square deviation between condition samples and the normality check were expounded emphatically. Then, the software for statistical analysis of B-basis value was developed based on the merging method of multiple condition samples. Finally, the software was used to statistically analyze the mechanical properties data of partial Jiangsu Hengshen Company Limited composites. The results show that comparing with the traditional single condition sample statistic program, the multiple condition samples merging method not only raises the B-basis value significantly, but also overcomes the limitation for number of samples and number of batches in traditional statistic program. The conclusions obtained show that this method has higher operability, and is applicable to the statistical analyses for B-basis values of composites in the case of reduced sample.
In order to reduce the test cost for obtaining the design allowables of composites, a regression analysis-based B-basis value statistical method merging multiple condition samples which was latest issued by Composite Material Handbook-17-G was introduced, and the rationality and applicable conditions for the addition of engineering experience judgment in the check of variation between batches, the equality check for square deviation between condition samples and the normality check were expounded emphatically. Then, the software for statistical analysis of B-basis value was developed based on the merging method of multiple condition samples. Finally, the software was used to statistically analyze the mechanical properties data of partial Jiangsu Hengshen Company Limited composites. The results show that comparing with the traditional single condition sample statistic program, the multiple condition samples merging method not only raises the B-basis value significantly, but also overcomes the limitation for number of samples and number of batches in traditional statistic program. The conclusions obtained show that this method has higher operability, and is applicable to the statistical analyses for B-basis values of composites in the case of reduced sample.
2016, 33(5): 1048-1054.
doi: 10.13801/j.cnki.fhclxb.20160121.003
Abstract:
In order to investigate the damage tolerance properties of 3D braided composites, first, four kinds of 3D braided composites and one kind of laminate composite which were made by the same kind of fiber, matrix and technology were fabricated respectively. Then, low velocity impact tests and compression after impact (CAI) tests of the same composite under different impact energies and different composites under the same impact energy were conducted. Finally, the C-scan damage detection after impact was conducted, and the dent depth, damage area and damage length after impact were also contrasted. The results show that the damage morphology of laminate composites are mainly oval-shaped and the delamination damage is severe, while most of the damage morphologies of 3D braided composites are cross-shaped, and the integrity of 3D braided composites is better. The impact energy inflection points for the laminate composite and 3D braided composites both appear at about 30 J. The compression residual strength of 3D braided composites is higher, and the damage tolerance properties are better than those of laminate composites. The conclusions obtained can provide guidances for the engineering application of 3D braided composites.
In order to investigate the damage tolerance properties of 3D braided composites, first, four kinds of 3D braided composites and one kind of laminate composite which were made by the same kind of fiber, matrix and technology were fabricated respectively. Then, low velocity impact tests and compression after impact (CAI) tests of the same composite under different impact energies and different composites under the same impact energy were conducted. Finally, the C-scan damage detection after impact was conducted, and the dent depth, damage area and damage length after impact were also contrasted. The results show that the damage morphology of laminate composites are mainly oval-shaped and the delamination damage is severe, while most of the damage morphologies of 3D braided composites are cross-shaped, and the integrity of 3D braided composites is better. The impact energy inflection points for the laminate composite and 3D braided composites both appear at about 30 J. The compression residual strength of 3D braided composites is higher, and the damage tolerance properties are better than those of laminate composites. The conclusions obtained can provide guidances for the engineering application of 3D braided composites.
2016, 33(5): 1055-1063.
doi: 10.13801/j.cnki.fhclxb.20160122.002
Abstract:
In order to improve the ratio of effective load to wing mass (load/mass ratio) of all-composite wing, a finite element simulate approach was proposed to predict the ultimate load of all-composite wing, and the structural design framework which can raise the structural efficiency of wing was established. First, based on the thin-walled engineering beam theory, theoretical analysis was conducted on all-composite wing, and the initial design of structure form and lay-ups form for all-composite wing was preceded. Then, based on the testing data of initial wing, four kinds of different finite element models were built using ABAQUS, and the best numerical simulate approach was obtained by contrast. After that, fourteen kinds of structure configuration forms were established and each structure form were given with different lay-up plans, thus one hundred and seventeen design plans for wing were formed, the load/mass ratios and manufacture factors of each structure form were contrasted. Finally, the all-composite wing was manufactured and test verification was conducted. The results show that double I-beam structure is the best structure configuration form of wing, which has relatively high load bearing efficiency. The relative error between simulated load and testing value is only 1.91%, which verifies the correctness of finite element model. The load/mass ratio of wing reaches 24.17 N/g, which is 30.65% higher comparing with that of the initial design. The conclusions obtained show that the design approach is valid.
In order to improve the ratio of effective load to wing mass (load/mass ratio) of all-composite wing, a finite element simulate approach was proposed to predict the ultimate load of all-composite wing, and the structural design framework which can raise the structural efficiency of wing was established. First, based on the thin-walled engineering beam theory, theoretical analysis was conducted on all-composite wing, and the initial design of structure form and lay-ups form for all-composite wing was preceded. Then, based on the testing data of initial wing, four kinds of different finite element models were built using ABAQUS, and the best numerical simulate approach was obtained by contrast. After that, fourteen kinds of structure configuration forms were established and each structure form were given with different lay-up plans, thus one hundred and seventeen design plans for wing were formed, the load/mass ratios and manufacture factors of each structure form were contrasted. Finally, the all-composite wing was manufactured and test verification was conducted. The results show that double I-beam structure is the best structure configuration form of wing, which has relatively high load bearing efficiency. The relative error between simulated load and testing value is only 1.91%, which verifies the correctness of finite element model. The load/mass ratio of wing reaches 24.17 N/g, which is 30.65% higher comparing with that of the initial design. The conclusions obtained show that the design approach is valid.
2016, 33(5): 1064-1071.
doi: 10.13801/j.cnki.fhclxb.20160112.002
Abstract:
In order to investigate the manufacture and free vibration of Ti-C fiber metal laminates (FMLs) which were prepared by alternated stacking arrangements of titanium alloy and carbon fiber reinforced plastics, the free vibration of Ti-C FMLs with different sizes were 2D finite element modeled and calculated using finite element analyses software MSC.PATRAN/NASTRAN firstly, and the influences of size effect on natural frequencies of FMLs were studied. Then, electromagnetic vibration exciter and non-contact laser scanner were used to conduct the free vibration tests, and the numerical simulated results were compared the testing results. Finally, the natural frequencies of pure carbon fiber composite laminates and Ti-C FMLs with different number of layers for titanium alloy laminates with the same size were calculated, and the effects of number of layers for titanium alloy laminates on natural frequencies of FMLs were investigated. The results show that the smaller the specimen size is, the bigger the calculation error of natural frequency is, namely, when the multiple of in-plane size to thickness of structure is relatively small, the calculation error of model is large. Over all, the numerical simulated results coincide with testing results preferably, and the finite element model is valid. The natural frequencies of FMLs decrease with the increase for number of layers for titanium alloy laminates. The conclusions obtained can provide reference to improve the design ability for free vibration of Ti-C FMLs.
In order to investigate the manufacture and free vibration of Ti-C fiber metal laminates (FMLs) which were prepared by alternated stacking arrangements of titanium alloy and carbon fiber reinforced plastics, the free vibration of Ti-C FMLs with different sizes were 2D finite element modeled and calculated using finite element analyses software MSC.PATRAN/NASTRAN firstly, and the influences of size effect on natural frequencies of FMLs were studied. Then, electromagnetic vibration exciter and non-contact laser scanner were used to conduct the free vibration tests, and the numerical simulated results were compared the testing results. Finally, the natural frequencies of pure carbon fiber composite laminates and Ti-C FMLs with different number of layers for titanium alloy laminates with the same size were calculated, and the effects of number of layers for titanium alloy laminates on natural frequencies of FMLs were investigated. The results show that the smaller the specimen size is, the bigger the calculation error of natural frequency is, namely, when the multiple of in-plane size to thickness of structure is relatively small, the calculation error of model is large. Over all, the numerical simulated results coincide with testing results preferably, and the finite element model is valid. The natural frequencies of FMLs decrease with the increase for number of layers for titanium alloy laminates. The conclusions obtained can provide reference to improve the design ability for free vibration of Ti-C FMLs.
2016, 33(5): 1072-1078.
doi: 10.13801/j.cnki.fhclxb.20160118.004
Abstract:
Through the determination of flexural strength, compressive strength test and matrix pH value test of glass fiber reinforced cement (GRC) specimens under different ages and ambient humidities, the effects of ambient humidity on the mechanical properties of GRC specimens blended with active mineral admixtures of fly ash and silica fume were researched. The results show that the ambient humidity has a significant effect on the flexural strength of GRC specimens. With the increase of the age, the higher relative humidity is, the more flexural strength of GRC specimens reduces. After 56 d age on the condition of temperature of 60℃ and relative humidity of 95%, the flexural strength and compressive strength of GRC specimens blended with 40% fly ash and 10% silica fume both increase by 48.5% and 23.6% respectively, meanwhile the pH value of GRC matrix decreases by 6% in comparison to those without fly ash and silica fume. On the same condition of ambient humidity, the pH values of specimens blended with fly ash and silica fume are lower than those of ordinary portland cement specimens in every age, which shows that the addition of fly ash and silica fume can reduce the alkalinity of cement hydration liquid phase and slow down the corrosion rate of fibers. So it can dramatically improve the mechanical property and durability of GRC specimens. Based on the analysis of the test results and MATLAB software, the mathematical relationship between the mechanical properties of GRC specimens including the flexural strength and compressive strength and the pH value of cement mortar matrix, the age can be established.
Through the determination of flexural strength, compressive strength test and matrix pH value test of glass fiber reinforced cement (GRC) specimens under different ages and ambient humidities, the effects of ambient humidity on the mechanical properties of GRC specimens blended with active mineral admixtures of fly ash and silica fume were researched. The results show that the ambient humidity has a significant effect on the flexural strength of GRC specimens. With the increase of the age, the higher relative humidity is, the more flexural strength of GRC specimens reduces. After 56 d age on the condition of temperature of 60℃ and relative humidity of 95%, the flexural strength and compressive strength of GRC specimens blended with 40% fly ash and 10% silica fume both increase by 48.5% and 23.6% respectively, meanwhile the pH value of GRC matrix decreases by 6% in comparison to those without fly ash and silica fume. On the same condition of ambient humidity, the pH values of specimens blended with fly ash and silica fume are lower than those of ordinary portland cement specimens in every age, which shows that the addition of fly ash and silica fume can reduce the alkalinity of cement hydration liquid phase and slow down the corrosion rate of fibers. So it can dramatically improve the mechanical property and durability of GRC specimens. Based on the analysis of the test results and MATLAB software, the mathematical relationship between the mechanical properties of GRC specimens including the flexural strength and compressive strength and the pH value of cement mortar matrix, the age can be established.
2016, 33(5): 1079-1086.
doi: 10.13801/j.cnki.fhclxb.20151126.002
Abstract:
Extreme high-temperature flight environment exposure of ultra-high temperature ceramic materials will result in their oxidations, and the generated oxide products on the surface which have different thermal-physical properties, thus will affect the heat transfer process. For pre-oxidized ZrB2 and ZrB2-SiC materials, the thickness of oxidation layer (ZrO2, B2O3, SiO2 and SiC-depleted layer) was calculated from oxidation models. Cylindrical representative volume unit was modeled using finite element, and it was coupled with an external hypersonic flow CFD (Computational Fluid Dynamics) solver to study the effects of high-temperature oxidation on coupled heat transfer of ultra-high temperature ceramic materials. Multi-field coupling calculation was implemented in conjunction with flow solver of Navier-Stokes equation and the finite element solver by using partition algorithm, and real time data exchange between non-matched meshes was achieved by interpolating data at coupling surface. All thermal-physical properties of ZrB2, ZrB2-SiC and oxidation products are temperature dependent. The effective thermal conductivity and effective heat capacity of porous medium, which are caused by the evaporation of B2O3 and the depletion of SiC, were calculated based on theoretical calculation. The transient coupled heat transfer analysis results indicate that, the thermal resistance of ZrB2 after preoxidation is slightly higher than that of original ZrB2, and there is little variation for thermal resistance of ZrB2-SiC materials before and after oxidation. Moreover, for the same flow environmental conditions, ZrB2 after oxidation has higher thermal resistance than ZrB2-SiC after oxidation.
Extreme high-temperature flight environment exposure of ultra-high temperature ceramic materials will result in their oxidations, and the generated oxide products on the surface which have different thermal-physical properties, thus will affect the heat transfer process. For pre-oxidized ZrB2 and ZrB2-SiC materials, the thickness of oxidation layer (ZrO2, B2O3, SiO2 and SiC-depleted layer) was calculated from oxidation models. Cylindrical representative volume unit was modeled using finite element, and it was coupled with an external hypersonic flow CFD (Computational Fluid Dynamics) solver to study the effects of high-temperature oxidation on coupled heat transfer of ultra-high temperature ceramic materials. Multi-field coupling calculation was implemented in conjunction with flow solver of Navier-Stokes equation and the finite element solver by using partition algorithm, and real time data exchange between non-matched meshes was achieved by interpolating data at coupling surface. All thermal-physical properties of ZrB2, ZrB2-SiC and oxidation products are temperature dependent. The effective thermal conductivity and effective heat capacity of porous medium, which are caused by the evaporation of B2O3 and the depletion of SiC, were calculated based on theoretical calculation. The transient coupled heat transfer analysis results indicate that, the thermal resistance of ZrB2 after preoxidation is slightly higher than that of original ZrB2, and there is little variation for thermal resistance of ZrB2-SiC materials before and after oxidation. Moreover, for the same flow environmental conditions, ZrB2 after oxidation has higher thermal resistance than ZrB2-SiC after oxidation.
2016, 33(5): 1087-1096.
doi: 10.13801/j.cnki.fhclxb.20151223.004
Abstract:
Palygorskite/carbon (PG/C) composites were synthesized via a hydrothermal route at 220℃ for 24 h using palygorskite and cellulose (PG) as raw materials. The obtained nano PG/C composites were introduced into the carbon/carbon (C/C) composites during the impregnation-carbonization process. Thus the C/C-ceramic/C composites were in-situ prepared by one-step hot pressing method. The mechanical and antioxidant properties were studied for C/C composites using PG/C as additives. The results show that the PG/C converts to enstatite/C during hot pressing process. The resulted enstatite/C enhances the mechanical properties of C/C composites by filling and bridging, and the nano C layer loading on the surface of enstatite ceramic avoids weak-binding between ceramic phase and C matrix. Along with the decrease of nano C loading on surface of PG/C, the strength of C/C increases gradually. The PG/C with C content of 13% exhibits flexural strength of 263 MPa and elastic modulus of 47 GPa. Compared to that of C/C without additive, the values increases by 45% and 42% respectively. Compared to that of C/C introduced PG as additive, the value increases by 16% and 27% respectively. Also, the antioxidant properties of C/C improve due to the doped PG/C. The mass loss reduces by 12%-18% at 1000℃.
Palygorskite/carbon (PG/C) composites were synthesized via a hydrothermal route at 220℃ for 24 h using palygorskite and cellulose (PG) as raw materials. The obtained nano PG/C composites were introduced into the carbon/carbon (C/C) composites during the impregnation-carbonization process. Thus the C/C-ceramic/C composites were in-situ prepared by one-step hot pressing method. The mechanical and antioxidant properties were studied for C/C composites using PG/C as additives. The results show that the PG/C converts to enstatite/C during hot pressing process. The resulted enstatite/C enhances the mechanical properties of C/C composites by filling and bridging, and the nano C layer loading on the surface of enstatite ceramic avoids weak-binding between ceramic phase and C matrix. Along with the decrease of nano C loading on surface of PG/C, the strength of C/C increases gradually. The PG/C with C content of 13% exhibits flexural strength of 263 MPa and elastic modulus of 47 GPa. Compared to that of C/C without additive, the values increases by 45% and 42% respectively. Compared to that of C/C introduced PG as additive, the value increases by 16% and 27% respectively. Also, the antioxidant properties of C/C improve due to the doped PG/C. The mass loss reduces by 12%-18% at 1000℃.
2016, 33(5): 1097-1103.
doi: 10.13801/j.cnki.fhclxb.20151201.003
Abstract:
Using γ-Y2Si2O7 and Y2O3-Al2O3-SiO2 ternary oxide powders as raw materials, a dense γ-Y2Si2O7 ceramic coating was fabricated on surface of porous Si3N4 by using a combined method of slurry spraying and high-temperature melt infiltration. The effects of the composition of raw materials and sintering temperature on structure, organization and thermal shock resistance of coating were studied systematically by XRD and SEM detection methods. The results show that a coating with double-layer structure of dense γ-Y2Si2O7 layer and transition layer is obtained when amount of substance ratio of SiO2 and Al2O3 is high. A single-layer structure is obtained when amount of substance ratio of SiO2 and Al2O3 is low. The coating with double-layer structure has a better thermal shock resistance property than the coating with single-layer structure.
Using γ-Y2Si2O7 and Y2O3-Al2O3-SiO2 ternary oxide powders as raw materials, a dense γ-Y2Si2O7 ceramic coating was fabricated on surface of porous Si3N4 by using a combined method of slurry spraying and high-temperature melt infiltration. The effects of the composition of raw materials and sintering temperature on structure, organization and thermal shock resistance of coating were studied systematically by XRD and SEM detection methods. The results show that a coating with double-layer structure of dense γ-Y2Si2O7 layer and transition layer is obtained when amount of substance ratio of SiO2 and Al2O3 is high. A single-layer structure is obtained when amount of substance ratio of SiO2 and Al2O3 is low. The coating with double-layer structure has a better thermal shock resistance property than the coating with single-layer structure.
2016, 33(5): 1104-1110.
doi: 10.13801/j.cnki.fhclxb.20151127.002
Abstract:
The feasibility of preparing flake absorbent by self-reactive spray forming technology and the effect of substrate on microstructure and electromagnetic properties of flake absorbent were studied. Fe+MnO2+Fe2O3+ZnO was treated as the reactive system. Substrates made of graphite, tungsten copper and brass materials were chosen to prepare the flake Mn-Zn ferrite absorbent based on mechanism of self-reactive spray forming technology. XRD and SEM were used to characterize the morphology phase and microstructure of the absorbent. The electromagnetic properties of the flake absorbent were tested by the web vector analyzers. The results show that, flake Mn-Zn ferrite absorbent can only be obviously acquired by brass substrate, and the absorption intensity and bandwidth of the absorbent prepared on brass is better than the other two kinds. It means that the choice of substrate has a great effect on both microstructure aspect and electromagnetic properties aspect of flake absorbent prepared by self-reactive spray forming technology.
The feasibility of preparing flake absorbent by self-reactive spray forming technology and the effect of substrate on microstructure and electromagnetic properties of flake absorbent were studied. Fe+MnO2+Fe2O3+ZnO was treated as the reactive system. Substrates made of graphite, tungsten copper and brass materials were chosen to prepare the flake Mn-Zn ferrite absorbent based on mechanism of self-reactive spray forming technology. XRD and SEM were used to characterize the morphology phase and microstructure of the absorbent. The electromagnetic properties of the flake absorbent were tested by the web vector analyzers. The results show that, flake Mn-Zn ferrite absorbent can only be obviously acquired by brass substrate, and the absorption intensity and bandwidth of the absorbent prepared on brass is better than the other two kinds. It means that the choice of substrate has a great effect on both microstructure aspect and electromagnetic properties aspect of flake absorbent prepared by self-reactive spray forming technology.
2016, 33(5): 1111-1118.
doi: 10.13801/j.cnki.fhclxb.20160121.004
Abstract:
In order to predict the elastic coefficients of composite single layer laminate containing voids, the unidirectional fiber reinforced composite single layer laminate were used as research object, and based on mesomechanics method, a prediction method for elastic coefficients of composite single layer laminate containing voids based on two-scale representative volume cells was proposed firstly. Then, based on the fibers distribution and void feature, representative volume element model on the fiber-matrix scale and representative volume element model of the composite single layer laminate containing voids were established, and finite element method was employed to solve the elastic coefficients. After that, with the periodic symmetry boundary conditions applied, the first step of equivalent was conducted on the fiber-matrix scale, thus the elastic coefficients of composite single layer laminate without voids were obtained. Finally, the second step of equivalent was conducted on the representative volume element model of composite single layer laminate containing voids, and the prediction for elastic coefficients of composite single layer laminate containing voids was finished. The results show that the calculated results obtained by using this method agree well with the test data. With the combination for elastic coefficients of fiber and matrix as well as the model of voids morphology, the method can reflect the effects of each factor on the elastic coefficients of composite single layer laminate.
In order to predict the elastic coefficients of composite single layer laminate containing voids, the unidirectional fiber reinforced composite single layer laminate were used as research object, and based on mesomechanics method, a prediction method for elastic coefficients of composite single layer laminate containing voids based on two-scale representative volume cells was proposed firstly. Then, based on the fibers distribution and void feature, representative volume element model on the fiber-matrix scale and representative volume element model of the composite single layer laminate containing voids were established, and finite element method was employed to solve the elastic coefficients. After that, with the periodic symmetry boundary conditions applied, the first step of equivalent was conducted on the fiber-matrix scale, thus the elastic coefficients of composite single layer laminate without voids were obtained. Finally, the second step of equivalent was conducted on the representative volume element model of composite single layer laminate containing voids, and the prediction for elastic coefficients of composite single layer laminate containing voids was finished. The results show that the calculated results obtained by using this method agree well with the test data. With the combination for elastic coefficients of fiber and matrix as well as the model of voids morphology, the method can reflect the effects of each factor on the elastic coefficients of composite single layer laminate.
2016, 33(5): 1119-1124.
doi: 10.13801/j.cnki.fhclxb.20151225.003
Abstract:
In order to matching design the stiffness of composite auxiliary spring, the structure of the main-auxiliary spring assembly structure, which includes a composite auxiliary spring, was designed. The equivalent load of the composite auxiliary spring was calculated by the concentrated load method. According to the change of the deflection of the original steel leaf spring, the equivalent stiffness of the composite auxiliary spring was estimated. The equivalent stiffness of the composite auxiliary spring was matching designed according to the design theory of steel leaf spring. The finite element simulation for the total stiffness of the main-auxiliary spring assembly was made by ABAQUS software. By adjusting the ply number of the composite auxiliary spring, the equivalent stiffness of the composite auxiliary spring was modified. The proposed matching design method processes great importance for the popularization and application of composite leaf spring.
In order to matching design the stiffness of composite auxiliary spring, the structure of the main-auxiliary spring assembly structure, which includes a composite auxiliary spring, was designed. The equivalent load of the composite auxiliary spring was calculated by the concentrated load method. According to the change of the deflection of the original steel leaf spring, the equivalent stiffness of the composite auxiliary spring was estimated. The equivalent stiffness of the composite auxiliary spring was matching designed according to the design theory of steel leaf spring. The finite element simulation for the total stiffness of the main-auxiliary spring assembly was made by ABAQUS software. By adjusting the ply number of the composite auxiliary spring, the equivalent stiffness of the composite auxiliary spring was modified. The proposed matching design method processes great importance for the popularization and application of composite leaf spring.
2016, 33(5): 1125-1131.
doi: 10.13801/j.cnki.fhclxb.20160112.003
Abstract:
In order to satisfy both stability and uniform coverage of the fiber trajectory, in contrast to the conventionally used geodesic winding, the equations of fiber patterns for non-geodesically filament-winding pressure vessels were proposed and the optimal design approaches for non-geodesic patterns and winding parameters were presented. The relative winding velocities of the mandrel and the feed eye for toroidal vessel were analyzed. The optimal patterns were adjusted according to the uniform coverage condition. Through the application of computer simulation techniques to the design and verification of toroidal vessel winding patterns, the CAD system was studied on the functions and implementation methods, the simulations of computer graphics and tests for non-geodesic filament-winding were realized. The results show that the designed non-geodesics satisfy the basic requirements for the winding process, and through the optimal non-geodesics winding patterns, the non-geodesic angles are centralizing around 55°, which are the optimal winding angle for cylindrical pressure vessels, and consequently improve the structural bearing capability of pressure vessels.
In order to satisfy both stability and uniform coverage of the fiber trajectory, in contrast to the conventionally used geodesic winding, the equations of fiber patterns for non-geodesically filament-winding pressure vessels were proposed and the optimal design approaches for non-geodesic patterns and winding parameters were presented. The relative winding velocities of the mandrel and the feed eye for toroidal vessel were analyzed. The optimal patterns were adjusted according to the uniform coverage condition. Through the application of computer simulation techniques to the design and verification of toroidal vessel winding patterns, the CAD system was studied on the functions and implementation methods, the simulations of computer graphics and tests for non-geodesic filament-winding were realized. The results show that the designed non-geodesics satisfy the basic requirements for the winding process, and through the optimal non-geodesics winding patterns, the non-geodesic angles are centralizing around 55°, which are the optimal winding angle for cylindrical pressure vessels, and consequently improve the structural bearing capability of pressure vessels.
2016, 33(5): 1132-1141.
doi: 10.13801/j.cnki.fhclxb.20160102.003
Abstract:
Two methods were applied including finite element analysis calculation and experimental testing to investigate the residual stress occurring fiber reinforce prepreg placement processing under coupled thermal-mechanical loading. Firstly, coupled thermo-mechanical model of fiber reinforce prepreg placement was built in order to investigate residual stress on the surface of the fiber reinforce prepreg placement under different temperature and pressure parameters using the finite element analysis. Secondly, the results were analyzed and compared to see the basic influence rule of various temperature and pressure parameters on residual stresses in fiber reinforce prepreg placement. Finally, experimental study on residual stresses influences under different temperature and pressure placement parameters were carried out in fiber reinforce prepreg placement to validate the correctness of calculation results by coupled thermo-mechanical finite element model. The results show that the distribution of residual stress of the experimental results is in consistent with the predicted results and only the difference can be seen for the maximum residual stress.
Two methods were applied including finite element analysis calculation and experimental testing to investigate the residual stress occurring fiber reinforce prepreg placement processing under coupled thermal-mechanical loading. Firstly, coupled thermo-mechanical model of fiber reinforce prepreg placement was built in order to investigate residual stress on the surface of the fiber reinforce prepreg placement under different temperature and pressure parameters using the finite element analysis. Secondly, the results were analyzed and compared to see the basic influence rule of various temperature and pressure parameters on residual stresses in fiber reinforce prepreg placement. Finally, experimental study on residual stresses influences under different temperature and pressure placement parameters were carried out in fiber reinforce prepreg placement to validate the correctness of calculation results by coupled thermo-mechanical finite element model. The results show that the distribution of residual stress of the experimental results is in consistent with the predicted results and only the difference can be seen for the maximum residual stress.
2016, 33(5): 1142-1146.
doi: 10.13801/j.cnki.fhclxb.20151225.002
Abstract:
In order to determine cross-section size parameters of the horizontal stabilizer plane of a certain aircraft, and validate that the simulation analysis method is reasonable and effective, axial compression stability of composite stiffened panel was studied by finite element buckling analysis and tests. Under the condition of the same support, it was researched that the tendency of the initial buckling and bearing capacity for composite stiffened panel caused by increasing the ratio of stringer cross-section area occupied the whole cross-section area. Test results show that test results and calculation results are consistent, which prove that the analysis method and analysis model are accurate and effective. The buckling loads would increase about 10.0% with the ratio of stringer cross-section area increasing 3.0%. This result would be used to guide the composite stiffened panel design work in aircraft type development, and provide reference for whose preliminary determination of the types and parameters of cross-section for horizontal stabilizer plane.
In order to determine cross-section size parameters of the horizontal stabilizer plane of a certain aircraft, and validate that the simulation analysis method is reasonable and effective, axial compression stability of composite stiffened panel was studied by finite element buckling analysis and tests. Under the condition of the same support, it was researched that the tendency of the initial buckling and bearing capacity for composite stiffened panel caused by increasing the ratio of stringer cross-section area occupied the whole cross-section area. Test results show that test results and calculation results are consistent, which prove that the analysis method and analysis model are accurate and effective. The buckling loads would increase about 10.0% with the ratio of stringer cross-section area increasing 3.0%. This result would be used to guide the composite stiffened panel design work in aircraft type development, and provide reference for whose preliminary determination of the types and parameters of cross-section for horizontal stabilizer plane.
