2016 Vol. 33, No. 2
2016, 33(2): 225-233.
doi: 10.13801/j.cnki.fhclxb.20150520.002
Abstract:
In order to investigate the size effects and strain rate sensitivity of Kevlar 49 single yarn, quasi-static (strain rate is 1/600 s-1) tensile tests were conducted on Kevlar 49 single yarns with different gauge lengths (25, 50, 100, 150, 200 and 300 mm) using MTS universal testing machine firstly. Then, dynamic (strain rate is 40-60 s-1) tensile tests were also conducted on samples whose gauge length is 25 mm by Instron drop-weight impact system. Finally, Weibull model was used in statistics analysis, and the degree of random variability in tensile strength of Kevlar 49 single yarns under different gauge lengths and strain rates was quantified. The results show that the tensile mechanical properties of Kevlar 49 single yarns have correlation with gauge length and strain rate. Tensile strength decreases with increasing gauge length, but increases with increasing strain rate. While ultimate strain and toughness both decrease with increasing gauge length and strain rate. The extract Weibull parameters can be used in numerical simulation and engineering application.
In order to investigate the size effects and strain rate sensitivity of Kevlar 49 single yarn, quasi-static (strain rate is 1/600 s-1) tensile tests were conducted on Kevlar 49 single yarns with different gauge lengths (25, 50, 100, 150, 200 and 300 mm) using MTS universal testing machine firstly. Then, dynamic (strain rate is 40-60 s-1) tensile tests were also conducted on samples whose gauge length is 25 mm by Instron drop-weight impact system. Finally, Weibull model was used in statistics analysis, and the degree of random variability in tensile strength of Kevlar 49 single yarns under different gauge lengths and strain rates was quantified. The results show that the tensile mechanical properties of Kevlar 49 single yarns have correlation with gauge length and strain rate. Tensile strength decreases with increasing gauge length, but increases with increasing strain rate. While ultimate strain and toughness both decrease with increasing gauge length and strain rate. The extract Weibull parameters can be used in numerical simulation and engineering application.
2016, 33(2): 234-239.
doi: 10.13801/j.cnki.fhclxb.20150528.002
Abstract:
Nano-MgO/high-density polyethylene (nano-MgO/HDPE) composites were prepared by melt blending method, and the mechanical properties of the composites were tested. The dispersity of nano-MgO in nano-MgO/HDPE composites was observed by SEM. The ultraviolet-shielding property, thermal stability and crystallization property of nano-MgO/HDPE composites were tested by ultraviolet-visible absorption spectra, TG and DSC respectively. The results show that although the addition of nano-MgO reduces the thermal decomposition temperature of HDPE, it improves the impact strength, flexural strength and ultraviolet-shielding property of HDPE. When the content of nano-MgO is 2wt%, the impact strength of nano-MgO/HDPE composite is 14% higher than that of pure HDPE. When the content of nano-MgO is 4wt%, the flexural strength of nano-MgO/HDPE composite is 18% higher than that of pure HDPE. The nano-MgO, which evenly distributed in nano-MgO/HDPE composites, promotes the crystallization of HDPE.
Nano-MgO/high-density polyethylene (nano-MgO/HDPE) composites were prepared by melt blending method, and the mechanical properties of the composites were tested. The dispersity of nano-MgO in nano-MgO/HDPE composites was observed by SEM. The ultraviolet-shielding property, thermal stability and crystallization property of nano-MgO/HDPE composites were tested by ultraviolet-visible absorption spectra, TG and DSC respectively. The results show that although the addition of nano-MgO reduces the thermal decomposition temperature of HDPE, it improves the impact strength, flexural strength and ultraviolet-shielding property of HDPE. When the content of nano-MgO is 2wt%, the impact strength of nano-MgO/HDPE composite is 14% higher than that of pure HDPE. When the content of nano-MgO is 4wt%, the flexural strength of nano-MgO/HDPE composite is 18% higher than that of pure HDPE. The nano-MgO, which evenly distributed in nano-MgO/HDPE composites, promotes the crystallization of HDPE.
2016, 33(2): 240-248.
doi: 10.13801/j.cnki.fhclxb.20150707.003
Abstract:
Silane coupling agent (APTES) was used as functional monomer to modify oxidation graphene(GO) and three kinds of silane coupling agent modification of GO (APTES-g-GO) nano-fillers have been prepared firstly under different experimental conditions. Then polystyrene (PS) composites filled with APTES-g-GO were fabricated by melt blending. To improve the compatibility of the blends, maleic anhydride grafted polyolefin (POE-g-MAH) was used as a compatibilizer. The morphology and properties of nano-fillers and the resultant nano APTES-g-GO/POE-g-MAH/PS composites have been characterized in detail by means of FTIR, XRD, TG, SEM, tensile and impact tests. The results indicate that APTES was successfully grafted onto the surface of GO. APTES shows some exfoliation and reduction effects to GO. Tensile strength and impact strength of the nano APTES-g-GO/POE-g-MAH/PS composites increase firstly, followed by decreasing with increasing nano-fillers content, and reach a maximum value at the 0.75% mass ratio of nano-filler content. Among them the nano AS-GO/POE-g-MAH/PS composites achieve the best comprehensive performance. The tensile strength and impact strength increase by 19% and 31%, respectively, compared with those of POE-g-MAH/PS. The reactions between the APTES-g-GO and POE-g-MAH take place during the blending process, which improve effectively the interfacial interactions of blending systems. APTES-g-GO disperse well in the composites. APTES-g-GO improve the thermal stability of composites, especially for the composite filled by AS-GO. The maximum thermal loss temperature of nano AS-GO/POE-g-MAH/PS composite with 0.75% mass ratio of AS-GO increases by 7 ℃ compared with that of POE-g-MAH/PS.
Silane coupling agent (APTES) was used as functional monomer to modify oxidation graphene(GO) and three kinds of silane coupling agent modification of GO (APTES-g-GO) nano-fillers have been prepared firstly under different experimental conditions. Then polystyrene (PS) composites filled with APTES-g-GO were fabricated by melt blending. To improve the compatibility of the blends, maleic anhydride grafted polyolefin (POE-g-MAH) was used as a compatibilizer. The morphology and properties of nano-fillers and the resultant nano APTES-g-GO/POE-g-MAH/PS composites have been characterized in detail by means of FTIR, XRD, TG, SEM, tensile and impact tests. The results indicate that APTES was successfully grafted onto the surface of GO. APTES shows some exfoliation and reduction effects to GO. Tensile strength and impact strength of the nano APTES-g-GO/POE-g-MAH/PS composites increase firstly, followed by decreasing with increasing nano-fillers content, and reach a maximum value at the 0.75% mass ratio of nano-filler content. Among them the nano AS-GO/POE-g-MAH/PS composites achieve the best comprehensive performance. The tensile strength and impact strength increase by 19% and 31%, respectively, compared with those of POE-g-MAH/PS. The reactions between the APTES-g-GO and POE-g-MAH take place during the blending process, which improve effectively the interfacial interactions of blending systems. APTES-g-GO disperse well in the composites. APTES-g-GO improve the thermal stability of composites, especially for the composite filled by AS-GO. The maximum thermal loss temperature of nano AS-GO/POE-g-MAH/PS composite with 0.75% mass ratio of AS-GO increases by 7 ℃ compared with that of POE-g-MAH/PS.
2016, 33(2): 249-258.
doi: 10.13801/j.cnki.fhclxb.20150518.006
Abstract:
Two kinds of silane coupling agents (KH550 and KH792) were applied to modify the surface of mesoporous molecular sieve MCM-41, and thus measurements including N2 adsorption-desorption, FTIR and TGA etc, were employed to characterize. The MCM-41/epoxy composite was prepared by in-situ polymerization method and the influences of coupling agent kinds and MCM-41 content on curing process and properties of composite were explored. The results show that the silane coupling agent could react with silicon hydroxyl of MCM-41 surface and thus the functional group is grafted to the internal and external surface of molecular sieve. The specific surface area of surface modified MCM-41 decreases to the one fifth of neat MCM-41 and the KH550 grafting ratio on surface of MCM-41 is just half of that in KH792.The reaction between KH550 and MCM-41 external surface is more ample and KH792 has more sufficient modification effect on internal wall of MCM-41 pore channel. The curing kinetics results show higher reaction activity of KH792 containing functional groups of the primary and secondary amine but hindering the epoxy macromolecule move into pore channel and thus MCM-41 is added as spherical particle in epoxy while the epoxy macromolecule could move into KH550 surface modified MCM-41 pore channel forming the interpenetrating structure. KH550 surface modified system improves the storage modulus and glass transition temperature greatly because the character of porous effect appears and organic-inorganic interpenetrating structure composite system forms. The character of KH792 surface modified system shows the conventional spherical nano particle and thus storage modulus and glass transition temperature have slight improvement compared to pure epoxy.
Two kinds of silane coupling agents (KH550 and KH792) were applied to modify the surface of mesoporous molecular sieve MCM-41, and thus measurements including N2 adsorption-desorption, FTIR and TGA etc, were employed to characterize. The MCM-41/epoxy composite was prepared by in-situ polymerization method and the influences of coupling agent kinds and MCM-41 content on curing process and properties of composite were explored. The results show that the silane coupling agent could react with silicon hydroxyl of MCM-41 surface and thus the functional group is grafted to the internal and external surface of molecular sieve. The specific surface area of surface modified MCM-41 decreases to the one fifth of neat MCM-41 and the KH550 grafting ratio on surface of MCM-41 is just half of that in KH792.The reaction between KH550 and MCM-41 external surface is more ample and KH792 has more sufficient modification effect on internal wall of MCM-41 pore channel. The curing kinetics results show higher reaction activity of KH792 containing functional groups of the primary and secondary amine but hindering the epoxy macromolecule move into pore channel and thus MCM-41 is added as spherical particle in epoxy while the epoxy macromolecule could move into KH550 surface modified MCM-41 pore channel forming the interpenetrating structure. KH550 surface modified system improves the storage modulus and glass transition temperature greatly because the character of porous effect appears and organic-inorganic interpenetrating structure composite system forms. The character of KH792 surface modified system shows the conventional spherical nano particle and thus storage modulus and glass transition temperature have slight improvement compared to pure epoxy.
2016, 33(2): 259-264.
doi: 10.13801/j.cnki.fhclxb.20150601.002
Abstract:
With the extensive application of fiber reinforced composites, the study on its dynamic mechanical properties under hygrothermal environment is provided with theory research significance and practical application value. Fristly, hygrothermal treatment was performed on carbon fiber reinforced epoxy (Carbon/Epoxy) composite laminate specimen. The high strain rate compression experiment of dry/wet state specimen was performed using split hopkinson pressure bar (SHPB) technology. And the experimental results were analyzed. The results indicate that a two stages characteristic is presented in the process of dehydration/rehydration of the material, with an effect of secondary dehydration/rehydration, the strength of Carbon/Epoxy composite laminates have the strain rate sensitivity in the vertical layer direction, the strength increases nearly threefold as the strain rate increase from 1 500 s-1 to 6 000 s-1, with an extremely slight change of the elastic modulus. Meanwhile, hygrothermal treatment can improve the dynamic mechanical performance of this kind of material. The material after 20 d moisture absorption exhibits the highest dynamical strength, up to 12.45% growth, and the rise of dynamical strength of material by moisture absorption is more obvious when the strain rate is relatively low.
With the extensive application of fiber reinforced composites, the study on its dynamic mechanical properties under hygrothermal environment is provided with theory research significance and practical application value. Fristly, hygrothermal treatment was performed on carbon fiber reinforced epoxy (Carbon/Epoxy) composite laminate specimen. The high strain rate compression experiment of dry/wet state specimen was performed using split hopkinson pressure bar (SHPB) technology. And the experimental results were analyzed. The results indicate that a two stages characteristic is presented in the process of dehydration/rehydration of the material, with an effect of secondary dehydration/rehydration, the strength of Carbon/Epoxy composite laminates have the strain rate sensitivity in the vertical layer direction, the strength increases nearly threefold as the strain rate increase from 1 500 s-1 to 6 000 s-1, with an extremely slight change of the elastic modulus. Meanwhile, hygrothermal treatment can improve the dynamic mechanical performance of this kind of material. The material after 20 d moisture absorption exhibits the highest dynamical strength, up to 12.45% growth, and the rise of dynamical strength of material by moisture absorption is more obvious when the strain rate is relatively low.
2016, 33(2): 265-272.
doi: 10.13801/j.cnki.fhclxb.20151014.001
Abstract:
During the hole-making process of carbon/epoxy (C/E) composites, many kinds of processing damages are easy to appear such as burr, spalling and delamination. Reasonable and effective evaluation of processing damages is an important guarantee for the economy and reliability of the composite components. Due to the singleness and limitation of the existing evaluation method of fiber reinforced composite hole-making damages, firstly, a new and comprehensive evaluation method, which based on the relative index in statistical analysis, was proposed by overall taking consideration of burr, spalling and delamination damages and a mathematical model of damage factor was proposed. Then, according to the relevance of the evaluation indexes, all coefficients in the mathematical model and the critical value of damage factor, which decided whether composite hole-making quality is qualified, were determined through tool wear tests. At last, the precision of the proposed method was verified by ultrasonic detection. Results show that the comprehensive evaluation method of C/E composite hole-making damage proposed could effectively reflect and assess the hole-making quality under different processing parameters.
During the hole-making process of carbon/epoxy (C/E) composites, many kinds of processing damages are easy to appear such as burr, spalling and delamination. Reasonable and effective evaluation of processing damages is an important guarantee for the economy and reliability of the composite components. Due to the singleness and limitation of the existing evaluation method of fiber reinforced composite hole-making damages, firstly, a new and comprehensive evaluation method, which based on the relative index in statistical analysis, was proposed by overall taking consideration of burr, spalling and delamination damages and a mathematical model of damage factor was proposed. Then, according to the relevance of the evaluation indexes, all coefficients in the mathematical model and the critical value of damage factor, which decided whether composite hole-making quality is qualified, were determined through tool wear tests. At last, the precision of the proposed method was verified by ultrasonic detection. Results show that the comprehensive evaluation method of C/E composite hole-making damage proposed could effectively reflect and assess the hole-making quality under different processing parameters.
2016, 33(2): 273-279.
doi: 10.13801/j.cnki.fhclxb.20150616.002
Abstract:
Waterborne sizing (DGEBA-MDI-TX100) of carbon fiber was designed and synthesized by using 4,4'-diphenylmethane diisocyanate (MDI) as chain extender and grafting the Triton X-100 (TX-100) on diglycidyl ether of bisphenol A (DGEBA). The carbon fiber surface was modified by the synthesized waterborne sizing, based on which carbon/epoxy composites were prepared by using epoxy resin as the matrix. The effects of waterborne sizing agent modified on carbon fiber surface properties and the interfacial properties of carbon fiber/epoxy resin composites were investigated. The results show that compared to the unmodified carbon fiber, wetting performance of carbon fiber has been greatly improved after modified by the sizing agents, the contact angle of modified carbon fiber and epoxy resin declined by 9.1%, and the interface shear strength of modified carbon fiber/epoxy resin composite material increases by 64.7%.
Waterborne sizing (DGEBA-MDI-TX100) of carbon fiber was designed and synthesized by using 4,4'-diphenylmethane diisocyanate (MDI) as chain extender and grafting the Triton X-100 (TX-100) on diglycidyl ether of bisphenol A (DGEBA). The carbon fiber surface was modified by the synthesized waterborne sizing, based on which carbon/epoxy composites were prepared by using epoxy resin as the matrix. The effects of waterborne sizing agent modified on carbon fiber surface properties and the interfacial properties of carbon fiber/epoxy resin composites were investigated. The results show that compared to the unmodified carbon fiber, wetting performance of carbon fiber has been greatly improved after modified by the sizing agents, the contact angle of modified carbon fiber and epoxy resin declined by 9.1%, and the interface shear strength of modified carbon fiber/epoxy resin composite material increases by 64.7%.
2016, 33(2): 280-286.
doi: 10.13801/j.cnki.fhclxb.20150522.002
Abstract:
In order to establish the relationship between residual stiffness, material damage quantity and residual life, failure modes of fiber-reinforced polymer (FRP) laminates under tension-tension fatigue load effect are divided into three types: inter fiber fracture, fiber random fracture and delamination. Based on the analysis of quantitative relationship between different failure modes and residual stiffness degradation quantity, a compound model of residual stiffness degradation, integrated each failure mode's influence, was put forward. This model is applicable to stage Ⅰ and Ⅱ, which occupy most of the life, avoids the influence of stiffness reduction uncertainty in stage Ⅲ. Normalization of residual stiffness degradation curve by time scale, eliminates individual specimens' dispersion effect, significantly reduces the dispersion. Statistical analysis was conducted for fatigue test results of four kinds of E-glass/Epoxy glass fiber composite laminates and three kinds of AS-4/polyether-ether-ketone (PEEK) carbon fiber composite laminates, which shows that the proposed model is suitable for an accurate description of the residual stiffness decline law of composites.
In order to establish the relationship between residual stiffness, material damage quantity and residual life, failure modes of fiber-reinforced polymer (FRP) laminates under tension-tension fatigue load effect are divided into three types: inter fiber fracture, fiber random fracture and delamination. Based on the analysis of quantitative relationship between different failure modes and residual stiffness degradation quantity, a compound model of residual stiffness degradation, integrated each failure mode's influence, was put forward. This model is applicable to stage Ⅰ and Ⅱ, which occupy most of the life, avoids the influence of stiffness reduction uncertainty in stage Ⅲ. Normalization of residual stiffness degradation curve by time scale, eliminates individual specimens' dispersion effect, significantly reduces the dispersion. Statistical analysis was conducted for fatigue test results of four kinds of E-glass/Epoxy glass fiber composite laminates and three kinds of AS-4/polyether-ether-ketone (PEEK) carbon fiber composite laminates, which shows that the proposed model is suitable for an accurate description of the residual stiffness decline law of composites.
2016, 33(2): 287-296.
doi: 10.13801/j.cnki.fhclxb.20150511.001
Abstract:
A novel silane coupling agent (CA-K), designed and synthesized by our team, which contains terminal-alkyne and aromatic amic acid groups, was employed to reinforce the interfacial bonding performances of quartz fiber(QF)/silicon-containing arylacetylene (PSA) composites at high-temperature. FTIR, DSC and TGA trace analysis indicate that the imide ring structure is formed in CA-K with PSA curing process, and CA-K takes part in the curing of PSA simultaneously. XPS analysis calculates that chemical boundings form between CA-K and fiber. The interfacial bonding strength of QF/PSA composites are improved after CA-K treatment. The interlaminar shear strength (ILSS) and flexual strength are increased by 34.7% and 40.4% compared with those of unmodified at room temperature and the retention ratios of ILSS and bending strength are 82.5% and 54.9% when the temperature rises up to 250 ℃, 85.1% and 64.2% when it is 500 ℃.
A novel silane coupling agent (CA-K), designed and synthesized by our team, which contains terminal-alkyne and aromatic amic acid groups, was employed to reinforce the interfacial bonding performances of quartz fiber(QF)/silicon-containing arylacetylene (PSA) composites at high-temperature. FTIR, DSC and TGA trace analysis indicate that the imide ring structure is formed in CA-K with PSA curing process, and CA-K takes part in the curing of PSA simultaneously. XPS analysis calculates that chemical boundings form between CA-K and fiber. The interfacial bonding strength of QF/PSA composites are improved after CA-K treatment. The interlaminar shear strength (ILSS) and flexual strength are increased by 34.7% and 40.4% compared with those of unmodified at room temperature and the retention ratios of ILSS and bending strength are 82.5% and 54.9% when the temperature rises up to 250 ℃, 85.1% and 64.2% when it is 500 ℃.
2016, 33(2): 297-303.
doi: 10.13801/j.cnki.fhclxb.20150417.006
Abstract:
We use carbon fiber-glass fiber in layer knitting in the warp hybrid unidirectional fabric with different mixed ratio to prepare hybrid fiber reinforced epoxy composites, the tensile property change and failure form of carbon fiber-glass fiber/epoxy composites with different hybrid structures and different mixed ratios were studied. The 0° tensile results show that in different hybrid structures of same hybrid fabric, completely aligned structure with the concentrations of carbon fiber has the highest strength, the strength of fabrics with different mixed ratios of completely aligned structure is the same. The modulus of carbon fiber-glass fiber/epoxy composites follow the laws of mixing. The 90° tensile results show that the interface bonding strength between fiber and resin is carbon fiber/resin > glass fiber/resin, the strength and modulus of carbon fiber-glass fiber/epoxy composites relate to the different interface forms on material thickness direction (single or alternating interface, the distribution position of carbon fiber or glass fiber), and the content of carbon fiber has nothing to do with it.
We use carbon fiber-glass fiber in layer knitting in the warp hybrid unidirectional fabric with different mixed ratio to prepare hybrid fiber reinforced epoxy composites, the tensile property change and failure form of carbon fiber-glass fiber/epoxy composites with different hybrid structures and different mixed ratios were studied. The 0° tensile results show that in different hybrid structures of same hybrid fabric, completely aligned structure with the concentrations of carbon fiber has the highest strength, the strength of fabrics with different mixed ratios of completely aligned structure is the same. The modulus of carbon fiber-glass fiber/epoxy composites follow the laws of mixing. The 90° tensile results show that the interface bonding strength between fiber and resin is carbon fiber/resin > glass fiber/resin, the strength and modulus of carbon fiber-glass fiber/epoxy composites relate to the different interface forms on material thickness direction (single or alternating interface, the distribution position of carbon fiber or glass fiber), and the content of carbon fiber has nothing to do with it.
2016, 33(2): 304-309.
doi: 10.13801/j.cnki.fhclxb.20150824.001
Abstract:
Constrained-layer damping composite structure was prepared with glass fiber reinforced resin as constrained layer main material, nitrile butadiene rubber as damping layer and steel plate as basic plate. Dynamic mechanical analyzer and cantilever beam resonance method were used to study the influence of temperature, stiffness of constrained layer and the structure of damping layers on damping effect of constrained-layer damping composite structure. The results show that the free damping composite plate exhibits highest damping range when the damping layer is in glass transition region and extends to the high elastic state region when pasted with glass fiber reinforced plastics as constrained layer. Increasing the thickness and porosity of damping layer will improve the damping property of constrained-layer composite plate. The effects of aluminum plate which pasted as constrained layer is particularly significant. Aluminum plate cannot be used as constrained layer because of the serious corrosion in sea-water and dry/wet cycling strong corrosion occasions. Anti-corrosion glass fiber reinforced plastics is preferred under these special occasions.
Constrained-layer damping composite structure was prepared with glass fiber reinforced resin as constrained layer main material, nitrile butadiene rubber as damping layer and steel plate as basic plate. Dynamic mechanical analyzer and cantilever beam resonance method were used to study the influence of temperature, stiffness of constrained layer and the structure of damping layers on damping effect of constrained-layer damping composite structure. The results show that the free damping composite plate exhibits highest damping range when the damping layer is in glass transition region and extends to the high elastic state region when pasted with glass fiber reinforced plastics as constrained layer. Increasing the thickness and porosity of damping layer will improve the damping property of constrained-layer composite plate. The effects of aluminum plate which pasted as constrained layer is particularly significant. Aluminum plate cannot be used as constrained layer because of the serious corrosion in sea-water and dry/wet cycling strong corrosion occasions. Anti-corrosion glass fiber reinforced plastics is preferred under these special occasions.
2016, 33(2): 310-317.
doi: 10.13801/j.cnki.fhclxb.20150528.001
Abstract:
The nylon 66 fiber-Q235 steel composite plate was made by electrostatic flocking technology, and the effect of different amount of adhesive coating on flocking fastness was studied. The morphology of villi layer was observed and analyzed by SEM, and the sound absorption properties of composite plate were measured by transfer function method in the frequency range of 200-6 300 Hz. The influences of flocking voltage, flocking time, plate spacing and fiber morphology structure on the sound absorption properties were analyzed. The results show that, flocking fastness increases with the increasing amount of adhesive coating, on the premise of no air bubbles, 100 g/m2 is the best coating amount. As flocking voltage increasing, sound absorption properties improve, change rate decreases and finally tends to be stable. As plate spacing increasing, sound absorption properties decreases, begins to decline slowly, then gradually speeds up. The best flocking parameters are flocking voltage of 90 kV, flocking time of 40 s, plate spacing of 10 cm. Fiber morphology structure also has obviously influence on the sound absorption properties of nylon 66 fiber-Q235 steel composite plate. Reduce the fiber length and fiber diameter both can improve the sound absorption coefficient of composite plate, the best fiber morphology structure parameters are length of 0.9 mm, diameter of 20 μm.
The nylon 66 fiber-Q235 steel composite plate was made by electrostatic flocking technology, and the effect of different amount of adhesive coating on flocking fastness was studied. The morphology of villi layer was observed and analyzed by SEM, and the sound absorption properties of composite plate were measured by transfer function method in the frequency range of 200-6 300 Hz. The influences of flocking voltage, flocking time, plate spacing and fiber morphology structure on the sound absorption properties were analyzed. The results show that, flocking fastness increases with the increasing amount of adhesive coating, on the premise of no air bubbles, 100 g/m2 is the best coating amount. As flocking voltage increasing, sound absorption properties improve, change rate decreases and finally tends to be stable. As plate spacing increasing, sound absorption properties decreases, begins to decline slowly, then gradually speeds up. The best flocking parameters are flocking voltage of 90 kV, flocking time of 40 s, plate spacing of 10 cm. Fiber morphology structure also has obviously influence on the sound absorption properties of nylon 66 fiber-Q235 steel composite plate. Reduce the fiber length and fiber diameter both can improve the sound absorption coefficient of composite plate, the best fiber morphology structure parameters are length of 0.9 mm, diameter of 20 μm.
2016, 33(2): 318-326.
doi: 10.13801/j.cnki.fhclxb.20150428.002
Abstract:
YBa2Cu3O7 (YBCO) powder was prepared by oxalate co-precipitation method. YBCO/Cu composites with different mass fractions were prepared by vacuum hot-pressed sintering method. The density, hardness and conductivity of YBCO/Cu composites were measured. The friction and wear test was performed on YBCO/Cu composites by MMU-5GA abrasion equipment. The microstructure, wear surface morphology and phase composition of YBCO powder and YBCO/Cu composites were characterized by the means of XRD, SEM and TEM. The influence of YBCO mass fraction on microstructures and properties of YBCO/Cu composites were investigated. The results indicate that the YBCO powder phase is Y123 phase with apparent layer structure, and powders are nano-scale particles with high purity and less impurity. The matrix structures of YBCO/Cu composites are obviously refined and the tribological performance are improved by adding YBCO nano-particles. With the increase of YBCO mass fraction, the uniformity of YBCO nano-particles in matrix reduces and particles agglomerates gradually, the conductivity and density of YBCO/Cu composites decrease, the hardness firstly increases then decreases, the friction coefficient gradually reduces. The friction and wear performance of 3% YBCO/Cu composite are best. The strength mechanisms of YBCO/Cu composites are Orowan strengthening, thermal mismatch strengthening and grain refinement strengthening.The dominant wear mechanisms are plastic deformation wear, abrasive wear and fatigue flaking.
YBa2Cu3O7 (YBCO) powder was prepared by oxalate co-precipitation method. YBCO/Cu composites with different mass fractions were prepared by vacuum hot-pressed sintering method. The density, hardness and conductivity of YBCO/Cu composites were measured. The friction and wear test was performed on YBCO/Cu composites by MMU-5GA abrasion equipment. The microstructure, wear surface morphology and phase composition of YBCO powder and YBCO/Cu composites were characterized by the means of XRD, SEM and TEM. The influence of YBCO mass fraction on microstructures and properties of YBCO/Cu composites were investigated. The results indicate that the YBCO powder phase is Y123 phase with apparent layer structure, and powders are nano-scale particles with high purity and less impurity. The matrix structures of YBCO/Cu composites are obviously refined and the tribological performance are improved by adding YBCO nano-particles. With the increase of YBCO mass fraction, the uniformity of YBCO nano-particles in matrix reduces and particles agglomerates gradually, the conductivity and density of YBCO/Cu composites decrease, the hardness firstly increases then decreases, the friction coefficient gradually reduces. The friction and wear performance of 3% YBCO/Cu composite are best. The strength mechanisms of YBCO/Cu composites are Orowan strengthening, thermal mismatch strengthening and grain refinement strengthening.The dominant wear mechanisms are plastic deformation wear, abrasive wear and fatigue flaking.
2016, 33(2): 327-333.
doi: 10.13801/j.cnki.fhclxb.20150520.001
Abstract:
In order to investigate the thermology properties of Ni-based Y2W3O12 composites, negative thermal expansion material Y2W3O12 was prepared by secondary solid-state method firstly. Then, Y2W3O12 was mixed with metal Ni, and by hot pressing sintering under the conditions of 1 200 ℃ and 50 MPa, 40vol% Y2W3O12/Ni composites were obtained. Finally, the compositions and thermal expansion properties of composites were investigated. The results indicate that during the hot pressing sintering process, comparing with the complex chemical reactions occurring in contrast sample 40vol% Y2W3O12/Cr composite, there is no reaction occurred between the two phases of 40vol% Y2W3O12/Ni composites, for the reducibility of Ni is weaker than that of W, which makes 40vol% Y2W3O12/Ni composite keeps the lower coefficient of thermal expansion. After several cycle annealing to release the thermal stress and remove the crystal water of Y2W3O12 phase, the coefficient of thermal expansion of 40vol% Y2W3O12/Ni composite in the temperature range of 170-800 ℃ tends to be stable, which is about 3.4×10-6 K-1 and close to the theoretical design value of 4.0×10-6 K-1.
In order to investigate the thermology properties of Ni-based Y2W3O12 composites, negative thermal expansion material Y2W3O12 was prepared by secondary solid-state method firstly. Then, Y2W3O12 was mixed with metal Ni, and by hot pressing sintering under the conditions of 1 200 ℃ and 50 MPa, 40vol% Y2W3O12/Ni composites were obtained. Finally, the compositions and thermal expansion properties of composites were investigated. The results indicate that during the hot pressing sintering process, comparing with the complex chemical reactions occurring in contrast sample 40vol% Y2W3O12/Cr composite, there is no reaction occurred between the two phases of 40vol% Y2W3O12/Ni composites, for the reducibility of Ni is weaker than that of W, which makes 40vol% Y2W3O12/Ni composite keeps the lower coefficient of thermal expansion. After several cycle annealing to release the thermal stress and remove the crystal water of Y2W3O12 phase, the coefficient of thermal expansion of 40vol% Y2W3O12/Ni composite in the temperature range of 170-800 ℃ tends to be stable, which is about 3.4×10-6 K-1 and close to the theoretical design value of 4.0×10-6 K-1.
2016, 33(2): 334-340.
doi: 10.13801/j.cnki.fhclxb.20150804.001
Abstract:
In order to research the interfacing connection mechanism between the reinforced particles and metal matrix of the metal matrix composites in a severe plastic deformation (SPD) process, equal channel angular pressing and torsion (ECAP-T) process was used to fabricate bulk 10wt% SiCP/Al matrix composites at lower heating temperature. And the interfacial reaction and element diffusion between SiC particles and pure Al, occurred by deformation of ECAP-T one, two and four passes, were investigated. The interface and element diffusion were studied by TEM and XPS. Results show that even at a lower processing temperature outside, Al can still react with SiO2 layer on the SiC particle surfaces and form an interface layer mainly made of Al2O3. The diffusion coefficient of Al is enhanced by about 1016 times during the ECAP-T deformation in comparison with the theoretically calculated value. The enhanced diffusion attribute to not only the increase of interface temperature but also the presence of a high density of lattice defects such as vacancies, dislocations produced by ECAP-T deformation.
In order to research the interfacing connection mechanism between the reinforced particles and metal matrix of the metal matrix composites in a severe plastic deformation (SPD) process, equal channel angular pressing and torsion (ECAP-T) process was used to fabricate bulk 10wt% SiCP/Al matrix composites at lower heating temperature. And the interfacial reaction and element diffusion between SiC particles and pure Al, occurred by deformation of ECAP-T one, two and four passes, were investigated. The interface and element diffusion were studied by TEM and XPS. Results show that even at a lower processing temperature outside, Al can still react with SiO2 layer on the SiC particle surfaces and form an interface layer mainly made of Al2O3. The diffusion coefficient of Al is enhanced by about 1016 times during the ECAP-T deformation in comparison with the theoretically calculated value. The enhanced diffusion attribute to not only the increase of interface temperature but also the presence of a high density of lattice defects such as vacancies, dislocations produced by ECAP-T deformation.
2016, 33(2): 341-349.
doi: 10.13801/j.cnki.fhclxb.20150417.004
Abstract:
With SiO2 as the carrier, decanoic acid-palmitic acid as phase change material, decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites were prepared by sol-gel method. The performance were tested and characterized by using isothermal moisture adsorption and desorption method, cooling curve method, FTIR, SEM, laser particle size analyzer(LPSA), BET, TGA and DSC etc. The results show that carrier material SiO2 of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites with cage structure have a large number of microporous forming 3D space grid structure. It can both package and constraint with phase change materials by physical chimeric way of decanoic acid-palmitic acid and SiO2, and adsorb water molecules by hydrophilic properties of SiO2. It has good heat-moisture property. Decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites have smooth surface with no obvious depression, particle size is small and has good uniformity (particle size is 82.14 nm, micropore volume is 0.010 7 mL/g, micropore specific surface area is 25.16 m2/g, micropore average diameter is 26.63 nm),and it belongs to nanoscale organic phase change core material/inorganic matrix composite; phase change temperature is 19.88-23.13 ℃, phase change latent heat is 38.55-42.56 J/g, mass fraction of decanoic acid-palmitic acid is about 31.59%, it meets the comfort of the human body temperature range and is suitable for widely use in construction field.
With SiO2 as the carrier, decanoic acid-palmitic acid as phase change material, decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites were prepared by sol-gel method. The performance were tested and characterized by using isothermal moisture adsorption and desorption method, cooling curve method, FTIR, SEM, laser particle size analyzer(LPSA), BET, TGA and DSC etc. The results show that carrier material SiO2 of decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites with cage structure have a large number of microporous forming 3D space grid structure. It can both package and constraint with phase change materials by physical chimeric way of decanoic acid-palmitic acid and SiO2, and adsorb water molecules by hydrophilic properties of SiO2. It has good heat-moisture property. Decanoic acid-palmitic acid/SiO2 phase change and humidity storage composites have smooth surface with no obvious depression, particle size is small and has good uniformity (particle size is 82.14 nm, micropore volume is 0.010 7 mL/g, micropore specific surface area is 25.16 m2/g, micropore average diameter is 26.63 nm),and it belongs to nanoscale organic phase change core material/inorganic matrix composite; phase change temperature is 19.88-23.13 ℃, phase change latent heat is 38.55-42.56 J/g, mass fraction of decanoic acid-palmitic acid is about 31.59%, it meets the comfort of the human body temperature range and is suitable for widely use in construction field.
2016, 33(2): 350-357.
doi: 10.13801/j.cnki.fhclxb.20150701.001
Abstract:
In order to investigate the effects of ceramic additives on the properties of Ti3SiC2 matrix composites, Ti3SiC2 material as well as SiC/Ti3SiC2, Al2O3/Ti3SiC2 and MgAl2O4/Ti3SiC2 composites whose ceramic additive contents were 30wt% were fabricated by reactived hot pressing sintering method firstly. Then, the mechanical properties and conductivities of the materials were tested, the oxidation resistance of Ti3SiC2 matrix composites was investigated in the temperature range of 1 373-1 773 K, and the phase compositions and microstructures of sintering samples were characterized. The results show that the main products of Ti3SiC2 after high temperature oxidation are TiO2 and SiO2. The oxidation layer can be divided into two layers of inner and outer, the inner layer consists by two-phase mixture of TiO2 and SiO2, and the outer layer is TiO2. A large number of apparent pores exist in oxide layers and the structure is relatively loose, which leads to the poor oxidation resistance. Comparing with Al2O3/Ti3SiC2 and MgAl2O4/Ti3SiC2 composites, SiC/Ti3SiC2 composite has better oxidation resistance.
In order to investigate the effects of ceramic additives on the properties of Ti3SiC2 matrix composites, Ti3SiC2 material as well as SiC/Ti3SiC2, Al2O3/Ti3SiC2 and MgAl2O4/Ti3SiC2 composites whose ceramic additive contents were 30wt% were fabricated by reactived hot pressing sintering method firstly. Then, the mechanical properties and conductivities of the materials were tested, the oxidation resistance of Ti3SiC2 matrix composites was investigated in the temperature range of 1 373-1 773 K, and the phase compositions and microstructures of sintering samples were characterized. The results show that the main products of Ti3SiC2 after high temperature oxidation are TiO2 and SiO2. The oxidation layer can be divided into two layers of inner and outer, the inner layer consists by two-phase mixture of TiO2 and SiO2, and the outer layer is TiO2. A large number of apparent pores exist in oxide layers and the structure is relatively loose, which leads to the poor oxidation resistance. Comparing with Al2O3/Ti3SiC2 and MgAl2O4/Ti3SiC2 composites, SiC/Ti3SiC2 composite has better oxidation resistance.
2016, 33(2): 358-365.
doi: 10.13801/j.cnki.fhclxb.20150520.003
Abstract:
SiBN(C) ceramic fibers have been certificated as a promising candidate for reinforced body in ceramic matrix composites, due to their excellent properties high temperature stability, high temperature creep resistance behavior as well as high temperature oxidation resistance etc. The thermal stability and microstructure of SiBN(C) ceramic fibers were analyzed. Moreover, the high temperature anti-oxidation process of SiBN(C) ceramic fibers was investigated at temperature range from 1 100 ℃ to 1 500 ℃, and the influence of carbon content on the dielectric properties of SiBN(C) ceramic fibers was also investigated. The results show that the SiBN(C) ceramic fibers treated upon thermally heating after 1 600 ℃ in N2 atmosphere retard amorphous structure. The HT-TGA results show that the SiBN(C) caramic fibers have good high temperature thermal stability, and mass loss of the ceramic fibers is only 1.5wt% (1 450 ℃, N2 atmosphere). Furthermore, SiBN(C) ceramic fibers show pronounced high-temperature oxidation resistance. The oxidized ceramic fibers with dense and crack-free structure are observed, moreover, the ceramic fibers still remain amorphous structure after oxidation treatment at 1 400 ℃ for 5 h in air, whereas the XRD analysis shows that oxidized samples start to occur skin-core structure and crystallize at 1 500 ℃ for 5 h. Moreover, the results of XRD and SEM associated with EDX show the majority of the oxidated sample surface is the crystallization of cristobalite. The dielectric property investigation of SiBN(C) ceramic fibers show that, dielectric constant and dielectric loss of SiBN(C) ceramic fibers are 2.1 and 0.001 7 (frequence is 10 GHz), respectively, when the C content is as low as 0.1wt%. The properties evaluation indicate the SiBN(C) ceramic fibers indeed satisfy the requirements that proposed as reinforcement of high temperature wave-transparent materials.
SiBN(C) ceramic fibers have been certificated as a promising candidate for reinforced body in ceramic matrix composites, due to their excellent properties high temperature stability, high temperature creep resistance behavior as well as high temperature oxidation resistance etc. The thermal stability and microstructure of SiBN(C) ceramic fibers were analyzed. Moreover, the high temperature anti-oxidation process of SiBN(C) ceramic fibers was investigated at temperature range from 1 100 ℃ to 1 500 ℃, and the influence of carbon content on the dielectric properties of SiBN(C) ceramic fibers was also investigated. The results show that the SiBN(C) ceramic fibers treated upon thermally heating after 1 600 ℃ in N2 atmosphere retard amorphous structure. The HT-TGA results show that the SiBN(C) caramic fibers have good high temperature thermal stability, and mass loss of the ceramic fibers is only 1.5wt% (1 450 ℃, N2 atmosphere). Furthermore, SiBN(C) ceramic fibers show pronounced high-temperature oxidation resistance. The oxidized ceramic fibers with dense and crack-free structure are observed, moreover, the ceramic fibers still remain amorphous structure after oxidation treatment at 1 400 ℃ for 5 h in air, whereas the XRD analysis shows that oxidized samples start to occur skin-core structure and crystallize at 1 500 ℃ for 5 h. Moreover, the results of XRD and SEM associated with EDX show the majority of the oxidated sample surface is the crystallization of cristobalite. The dielectric property investigation of SiBN(C) ceramic fibers show that, dielectric constant and dielectric loss of SiBN(C) ceramic fibers are 2.1 and 0.001 7 (frequence is 10 GHz), respectively, when the C content is as low as 0.1wt%. The properties evaluation indicate the SiBN(C) ceramic fibers indeed satisfy the requirements that proposed as reinforcement of high temperature wave-transparent materials.
2016, 33(2): 366-372.
doi: 10.13801/j.cnki.fhclxb.20150508.001
Abstract:
In order to reduce the sintering temperature of CaSiO3 ceramic, by adding 1wt% Al2O3 and different amounts of V2O5 into CaSiO3 powders, the effects of V2O5 additive amount on the sintering behavior, microstructure and microwave dielectric properties of CaSiO3 ceramics were investigated. The results show that the appropriate addition of V2O5 can not only reduces the sintering temperature of V2O5-Al2O3/CaSiO3 ceramics from 1 250 ℃ to 1 000 ℃, but also restrict the abnormal growth of CaSiO3 ceramic grains and refine the ceramic grains. In the sintering process, V2O5 will melt and promote the densification process of CaSiO3 ceramic by liquid phase wetting effect. At the same time, some of V2O5 will volatilize, and the non-volatilized V2O5 will react with the matrix material to form the second phase, and the emergence of the second phase reduces the quality factor of the ceramic substantially. Taking the sintering behavior and microwave dielectric properties into consideration synthetically, when V2O5 additive amount is 6wt%, the V2O5-Al2O3/CaSiO3 ceramic sintered at 1 075 ℃ for 2 h has favorable comprehensive properties, the dielectric constant is 7.38 and the quality factor is 21 218 GHz.
In order to reduce the sintering temperature of CaSiO3 ceramic, by adding 1wt% Al2O3 and different amounts of V2O5 into CaSiO3 powders, the effects of V2O5 additive amount on the sintering behavior, microstructure and microwave dielectric properties of CaSiO3 ceramics were investigated. The results show that the appropriate addition of V2O5 can not only reduces the sintering temperature of V2O5-Al2O3/CaSiO3 ceramics from 1 250 ℃ to 1 000 ℃, but also restrict the abnormal growth of CaSiO3 ceramic grains and refine the ceramic grains. In the sintering process, V2O5 will melt and promote the densification process of CaSiO3 ceramic by liquid phase wetting effect. At the same time, some of V2O5 will volatilize, and the non-volatilized V2O5 will react with the matrix material to form the second phase, and the emergence of the second phase reduces the quality factor of the ceramic substantially. Taking the sintering behavior and microwave dielectric properties into consideration synthetically, when V2O5 additive amount is 6wt%, the V2O5-Al2O3/CaSiO3 ceramic sintered at 1 075 ℃ for 2 h has favorable comprehensive properties, the dielectric constant is 7.38 and the quality factor is 21 218 GHz.
2016, 33(2): 373-378.
doi: 10.13801/j.cnki.fhclxb.20150611.002
Abstract:
Carbon fiber needling preform was used to prepare C/C-SiC and C/C-SiC-ZrC ceramics matrix composites by precursor infiltration and pyrolysis (PIP) process respectively. The microstructure, mechanical and ablation properties of materials were analyzed and compared. The results show that the composites produced by the method have sufficient filling and homogeneity distribution of ceramic phase. The in-plane flexural strength, compression strength through thickness direction and interlaminar shear strength of C/C-SiC-ZrC are all lower than the corresponding properties of C/C-SiC. C/C-SiC-ZrC shows better anti-ablative preformances compared with C/C-SiC after ablation at 2 200 ℃ for 600 s, the linear ablation rate is reduced by 43.8% and the mass ablation rate is reduced by 25%. During ultra-high temperature stage, the ZrC and SiC in the matrix of C/C-SiC composites are oxidized into ZrO2 and SiO2, which form a kind of viscous binary glassy mixture. The mixture could effectively prevent oxidizing atmosphere into the matrix.
Carbon fiber needling preform was used to prepare C/C-SiC and C/C-SiC-ZrC ceramics matrix composites by precursor infiltration and pyrolysis (PIP) process respectively. The microstructure, mechanical and ablation properties of materials were analyzed and compared. The results show that the composites produced by the method have sufficient filling and homogeneity distribution of ceramic phase. The in-plane flexural strength, compression strength through thickness direction and interlaminar shear strength of C/C-SiC-ZrC are all lower than the corresponding properties of C/C-SiC. C/C-SiC-ZrC shows better anti-ablative preformances compared with C/C-SiC after ablation at 2 200 ℃ for 600 s, the linear ablation rate is reduced by 43.8% and the mass ablation rate is reduced by 25%. During ultra-high temperature stage, the ZrC and SiC in the matrix of C/C-SiC composites are oxidized into ZrO2 and SiO2, which form a kind of viscous binary glassy mixture. The mixture could effectively prevent oxidizing atmosphere into the matrix.
2016, 33(2): 379-385.
doi: 10.13801/j.cnki.fhclxb.20150703.002
Abstract:
To study the influence of eccentricity on eccentric compressive mechanical performance of glulam bamboo columns, six glulam bamboo columns were tested under eccentric loading. The results show that the failure modes of specimens mainly display as tensile fracture of bamboo fibers in the middle region of columns under eccentric loading. With the increase of eccentricity ratio, the peak load reduces, whereas axial displacement and lateral deflection at the middle cross-section corresponding to the peak load increase, and the flexural deformation is significant. At the peak load point, the bamboo compressive strain of eccentric compression specimens is much greater than that of axial compression specimen, the former is 3.1-4.6 times that of the latter, and the compressive deformation ability and strength are developed fully in the compression zone for glulam bamboo columns under eccentric loading. Based on the testing results and theoretical analysis, the calculation methods to predict the ultimate bearing capacity of the glulam bamboo columns under eccentric compression was proposed, and the mean absolute error is less 5% indicating that the calculated results are consistent with the testing results.
To study the influence of eccentricity on eccentric compressive mechanical performance of glulam bamboo columns, six glulam bamboo columns were tested under eccentric loading. The results show that the failure modes of specimens mainly display as tensile fracture of bamboo fibers in the middle region of columns under eccentric loading. With the increase of eccentricity ratio, the peak load reduces, whereas axial displacement and lateral deflection at the middle cross-section corresponding to the peak load increase, and the flexural deformation is significant. At the peak load point, the bamboo compressive strain of eccentric compression specimens is much greater than that of axial compression specimen, the former is 3.1-4.6 times that of the latter, and the compressive deformation ability and strength are developed fully in the compression zone for glulam bamboo columns under eccentric loading. Based on the testing results and theoretical analysis, the calculation methods to predict the ultimate bearing capacity of the glulam bamboo columns under eccentric compression was proposed, and the mean absolute error is less 5% indicating that the calculated results are consistent with the testing results.
2016, 33(2): 386-393.
doi: 10.13801/j.cnki.fhclxb.20150420.001
Abstract:
The longitudinal tensile-tensile fatigue characteristics and in-plane shear tensile-tensile fatigue characteristics of unidirectional C/C composites and the longitudinal tensile-tensile fatigue characteristics of three-dimensional and four-directional braided C/C composites were researched through tests. The interface residual strength between fiber bundle and matrix was measured. The residual stiffness degradation model and the residual strength degradation model under longitudinal and in-plane shear tensile-tensile fatigue loading of unidirectional C/C composites were fitted by the least square method, and the interface residual strength model between fiber bundle and matrix was established. The results show that the biggest stiffness degradation of the unidirectional C/C composites at the fatigue load stress level of 87.5% is only about 8.8%, whereas, the biggest in-plane shear stiffness degradation goes to about 30% at the fatigue load stress level of 70.0%. The strength and stiffness of three-dimensional and four-directional braided C/C composites are both improved after fatigue loading. The interface strength between fiber bundle and matrix of the three-dimensional and four-directional braided C/C composites decrease gradually with the increase of fatigue loading cycles.
The longitudinal tensile-tensile fatigue characteristics and in-plane shear tensile-tensile fatigue characteristics of unidirectional C/C composites and the longitudinal tensile-tensile fatigue characteristics of three-dimensional and four-directional braided C/C composites were researched through tests. The interface residual strength between fiber bundle and matrix was measured. The residual stiffness degradation model and the residual strength degradation model under longitudinal and in-plane shear tensile-tensile fatigue loading of unidirectional C/C composites were fitted by the least square method, and the interface residual strength model between fiber bundle and matrix was established. The results show that the biggest stiffness degradation of the unidirectional C/C composites at the fatigue load stress level of 87.5% is only about 8.8%, whereas, the biggest in-plane shear stiffness degradation goes to about 30% at the fatigue load stress level of 70.0%. The strength and stiffness of three-dimensional and four-directional braided C/C composites are both improved after fatigue loading. The interface strength between fiber bundle and matrix of the three-dimensional and four-directional braided C/C composites decrease gradually with the increase of fatigue loading cycles.
2016, 33(2): 394-398.
doi: 10.13801/j.cnki.fhclxb.20150623.001
Abstract:
The tensile stiffness of unidirectional and multi-directional hybrid fiber composites was studied. The influence of hybrid ratio and dispersion degree on hybrid effect was considered on basis of hybrid law and the prediction formula of the tensile modulus of unidirectional hybrid fiber composites was proposed. Tensile modulus of multi-directional hybrid fiber composites was obtained by experiment and estimated with the classical laminate theory. Based on the effects that hybrid ratio and dispersion degree have on the tensile modulus, the estimation formula of tensile modulus of multi-directional hybrid fiber composites was corrected. The result shows that the tensile modulus of hybrid fiber composites relates to the hybrid ratio and dispersion degree, the increase of dispersion degree can improve the longitudinal tensile modulus of unidirectional hybrid fiber composites to some extent. The tensile modulus dotained by classical laminate theory has an error compared with the experiment value, while by using the proposed formula, the tensile modulus of hybrid fiber composites can be estimated more exactly.
The tensile stiffness of unidirectional and multi-directional hybrid fiber composites was studied. The influence of hybrid ratio and dispersion degree on hybrid effect was considered on basis of hybrid law and the prediction formula of the tensile modulus of unidirectional hybrid fiber composites was proposed. Tensile modulus of multi-directional hybrid fiber composites was obtained by experiment and estimated with the classical laminate theory. Based on the effects that hybrid ratio and dispersion degree have on the tensile modulus, the estimation formula of tensile modulus of multi-directional hybrid fiber composites was corrected. The result shows that the tensile modulus of hybrid fiber composites relates to the hybrid ratio and dispersion degree, the increase of dispersion degree can improve the longitudinal tensile modulus of unidirectional hybrid fiber composites to some extent. The tensile modulus dotained by classical laminate theory has an error compared with the experiment value, while by using the proposed formula, the tensile modulus of hybrid fiber composites can be estimated more exactly.
2016, 33(2): 399-407.
doi: 10.13801/j.cnki.fhclxb.20150624.001
Abstract:
The shear properties of composite stiffened panel with cover were investigated through tests and finite element methods. Based on the finite element model of composite stiffened panel with cover and by removing cover, the finite element simulation analysis was conducted on large opening composite stiffened panel without cover to investigate the effects of cover on composite stiffened panel with cover. Test and numerical calculation results reflect that different regions of composite stiffened panel with cover buckles simultaneously and the final failure position is at the composite panel area outside the stiffeners. When the cover is removed, the rigidity and load-carrying capacity of structure get reduced, and the stress concentration point and location of the initial damage of structure both get shifted. The failure modes show no obvious change when failure, both are local buckling.
The shear properties of composite stiffened panel with cover were investigated through tests and finite element methods. Based on the finite element model of composite stiffened panel with cover and by removing cover, the finite element simulation analysis was conducted on large opening composite stiffened panel without cover to investigate the effects of cover on composite stiffened panel with cover. Test and numerical calculation results reflect that different regions of composite stiffened panel with cover buckles simultaneously and the final failure position is at the composite panel area outside the stiffeners. When the cover is removed, the rigidity and load-carrying capacity of structure get reduced, and the stress concentration point and location of the initial damage of structure both get shifted. The failure modes show no obvious change when failure, both are local buckling.
In-plane compressive properties for isosceles-trapezoid honeycomb core of glass steel sandwich panel
2016, 33(2): 408-417.
doi: 10.13801/j.cnki.fhclxb.20150528.003
Abstract:
In order to investigate the in-plane compressive failure mechanisms for isosceles-trapezoid honeycomb core of glass steel sandwich panels, the testing measurement on in-plane compressive properties of sandwich panel were conducted by material testing machine, and simulated investigation were carried out. The results show that the in-plane compressive damage ways of sandwich panels have three types of panel breaking, buckling instability of sandwich panel and deboning between panel and honeycomb core in sandwich panel. Panel is the main load bearing component of sandwich panel in-plane compression, and the honeycomb core function by clamped effect to the panel. The structural parameters and material parameters of panel are the main factors which influence the compressive strength and compressive rigidity for in-plane compression of sandwich panels. The structural parameters and material parameters of majority honeycomb core have little influence on compressive strength for in-plane compression of sandwich panels, but the structural parameters of individual honeycomb core have relatively remarkable influences on compressive rigidity for in-plane compression of sandwich panels. When the volume of sandwich panel is constant, the compressive strength and compressive rigidity for in-plane compression of sandwich panels increase gradually with honeycomb core unit cell body number increasing.
In order to investigate the in-plane compressive failure mechanisms for isosceles-trapezoid honeycomb core of glass steel sandwich panels, the testing measurement on in-plane compressive properties of sandwich panel were conducted by material testing machine, and simulated investigation were carried out. The results show that the in-plane compressive damage ways of sandwich panels have three types of panel breaking, buckling instability of sandwich panel and deboning between panel and honeycomb core in sandwich panel. Panel is the main load bearing component of sandwich panel in-plane compression, and the honeycomb core function by clamped effect to the panel. The structural parameters and material parameters of panel are the main factors which influence the compressive strength and compressive rigidity for in-plane compression of sandwich panels. The structural parameters and material parameters of majority honeycomb core have little influence on compressive strength for in-plane compression of sandwich panels, but the structural parameters of individual honeycomb core have relatively remarkable influences on compressive rigidity for in-plane compression of sandwich panels. When the volume of sandwich panel is constant, the compressive strength and compressive rigidity for in-plane compression of sandwich panels increase gradually with honeycomb core unit cell body number increasing.
2016, 33(2): 418-429.
doi: 10.13801/j.cnki.fhclxb.20150612.002
Abstract:
The aim for lightweight structure is the eternal subject for the developing of aeronautics and astronautics, corrugated sandwich cylindrical shell as a common form of lightweight construction has great potential infields of aeronautics and astronautics. The longitudinal and circular carbon fiber composite corrugated sandwich cylindrical shells were fabricated by hot press method. The corrugated cores and skins were made in integral and split forming, separately. The axial compressive mechanical properties of longitudinal and circular corrugated sandwich cylindrical shells were analyzed using the classic theory of plate and shell buckling. Ultimate load theoretical equations were obtained under four kinds of failure modes including Euler buckling, overall buckling, local buckling and face crushing. The failure mechanism maps of structure have been drawn which obviously show the relationship between failure modes and specimen size. The axial compression tests have been conducted on the longitudinal and circular corrugated sandwich cylindrical shell, the load-displacement curves and two kinds of failure modes including local buckling and face crushing have been obtained. The results show that longitudinal corrugated sandwich cylindrical shells is better than that of circular corrugated sandwich cylindrical shells in axial bearing load and efficiency of load/mass. Increase the thickness of cylindrical shell panel or decrease the height of cylindrical shell in a certain range can improve the efficiency of load/mass for structure.
The aim for lightweight structure is the eternal subject for the developing of aeronautics and astronautics, corrugated sandwich cylindrical shell as a common form of lightweight construction has great potential infields of aeronautics and astronautics. The longitudinal and circular carbon fiber composite corrugated sandwich cylindrical shells were fabricated by hot press method. The corrugated cores and skins were made in integral and split forming, separately. The axial compressive mechanical properties of longitudinal and circular corrugated sandwich cylindrical shells were analyzed using the classic theory of plate and shell buckling. Ultimate load theoretical equations were obtained under four kinds of failure modes including Euler buckling, overall buckling, local buckling and face crushing. The failure mechanism maps of structure have been drawn which obviously show the relationship between failure modes and specimen size. The axial compression tests have been conducted on the longitudinal and circular corrugated sandwich cylindrical shell, the load-displacement curves and two kinds of failure modes including local buckling and face crushing have been obtained. The results show that longitudinal corrugated sandwich cylindrical shells is better than that of circular corrugated sandwich cylindrical shells in axial bearing load and efficiency of load/mass. Increase the thickness of cylindrical shell panel or decrease the height of cylindrical shell in a certain range can improve the efficiency of load/mass for structure.
