2006 Vol. 23, No. 2
2006, 23(2): 1-8.
Abstract:
The uniaxial st rain cyclic characteristics and ratcheting behavior of T6-t reated SiCP / 6061Al alloy composites were experimentally studied at high temperature (300 ℃) . The cyclic sof tening/ hardening feature and ratcheting behavior of the composites containing two kinds of particulate volume f ractions were discussed under differentloading conditions at high temperature. It is shown that the particulate reinforced metal mat rix composites showsimilar st rain cyclic characteristics and ratcheting behavior to those of metals on a macro-scale. Namely , the ratcheting also occurs in the composites under asymmet rical cyclic st ressing , and the ratcheting st rain increases with theincrease of the st ress amplitude and mean st ress ; however , the addition of SiC particulates into the mat rix increasesthe resistance of the composites to ratcheting , and the ratcheting st rain decreases with the increase of the volumef raction of SiC particulates ; at 300 ℃, the ratcheting has great time2dependence , i. e. , the ratcheting st rain dependsgreatly on the st ressing rate and hold-time at peak st ress , and an interaction of creep and ratcheting is remarkable.The effect s of microst ructure features of the composite , loading condition and time on the ratcheting should be wellconsidered when t rying to const ruct a constitutive model to describe such ratcheting.
The uniaxial st rain cyclic characteristics and ratcheting behavior of T6-t reated SiCP / 6061Al alloy composites were experimentally studied at high temperature (300 ℃) . The cyclic sof tening/ hardening feature and ratcheting behavior of the composites containing two kinds of particulate volume f ractions were discussed under differentloading conditions at high temperature. It is shown that the particulate reinforced metal mat rix composites showsimilar st rain cyclic characteristics and ratcheting behavior to those of metals on a macro-scale. Namely , the ratcheting also occurs in the composites under asymmet rical cyclic st ressing , and the ratcheting st rain increases with theincrease of the st ress amplitude and mean st ress ; however , the addition of SiC particulates into the mat rix increasesthe resistance of the composites to ratcheting , and the ratcheting st rain decreases with the increase of the volumef raction of SiC particulates ; at 300 ℃, the ratcheting has great time2dependence , i. e. , the ratcheting st rain dependsgreatly on the st ressing rate and hold-time at peak st ress , and an interaction of creep and ratcheting is remarkable.The effect s of microst ructure features of the composite , loading condition and time on the ratcheting should be wellconsidered when t rying to const ruct a constitutive model to describe such ratcheting.
2006, 23(2): 9-13.
Abstract:
Two kinds of isot ropical conductive adhesives ( ICA) were developed by using carbon nanotubes (CNTs)and silver coated carbon nanotubes (SCCNTs) as conductive fillers. The elect rical , mechanical and aging propertiesof the above ICAs were investigated and compared with those of conventional ICA filled with 1μm average-sized Agparticles. The result s indicated that the percolation threshold of bulk resistivity reaches 2. 4 ×10-3Ω·cm for ICAwith 31 % filler content of CNTs and the shear st rength of ICA with 23 % filler content of CNTs approaches themaximum value. At the same filler content of 28 % , the ICAs filled with SCCNTs show the lowest conductive resistivity of 212 ×10-4Ω·cm and the ICAs filled with both CNTs and SCCNTs exhibit higher shear st rength of 19. 6MPa. The result s of aging properties tested under the conditions of 85 ℃, RH85 % for 1000h showed that the shif t sof both bulk resistivity and shear st rength do not exceed 10 % for the ICAs filled with both CNTs and SCCNTs ,while the shif t s of conductive resistivity and shear st rength are 350 % and 120 % , respectively , for ICA filled withmicro-sized Ag particles.
Two kinds of isot ropical conductive adhesives ( ICA) were developed by using carbon nanotubes (CNTs)and silver coated carbon nanotubes (SCCNTs) as conductive fillers. The elect rical , mechanical and aging propertiesof the above ICAs were investigated and compared with those of conventional ICA filled with 1μm average-sized Agparticles. The result s indicated that the percolation threshold of bulk resistivity reaches 2. 4 ×10-3Ω·cm for ICAwith 31 % filler content of CNTs and the shear st rength of ICA with 23 % filler content of CNTs approaches themaximum value. At the same filler content of 28 % , the ICAs filled with SCCNTs show the lowest conductive resistivity of 212 ×10-4Ω·cm and the ICAs filled with both CNTs and SCCNTs exhibit higher shear st rength of 19. 6MPa. The result s of aging properties tested under the conditions of 85 ℃, RH85 % for 1000h showed that the shif t sof both bulk resistivity and shear st rength do not exceed 10 % for the ICAs filled with both CNTs and SCCNTs ,while the shif t s of conductive resistivity and shear st rength are 350 % and 120 % , respectively , for ICA filled withmicro-sized Ag particles.
2006, 23(2): 14-20.
Abstract:
In order to investigate the relation between mechanical property and microst ructure of in2si tu synthesized Ti mat rix composites reinforced by both short-fiber-like TiB and particle-like TiC , a 3D cell model was developed on the basis of the RSA ( Random Sequential Adsorption) method , according to observed microst ructures.This model can be used to generate a multi2inclusion cell with both randomly dist ributed short -fiber -like and theparticle-like reinforcement s , and that the aspect ratio of short-fiber-like reinforcement s and the dist ribution rule canbe arbit rarily set . While compared with the experimental result s , the simulation result s obtained using this modelare relatively accurate. The result s show that : in the short-fiber-like reinforcement s , the ones parallel to the direc2tion of the applied st ress bear the most st ress , while the ones at an angle of about 45 degrees with the direction ofthe applied st ress bear the least . The particle-like ones bear much less st ress than the short-fiber-like ones parallelto the direction of the applied st ress. The st ress in the mat rix is higher in the local where the reinforcement s arecompact along the direction of the applied st ress.
In order to investigate the relation between mechanical property and microst ructure of in2si tu synthesized Ti mat rix composites reinforced by both short-fiber-like TiB and particle-like TiC , a 3D cell model was developed on the basis of the RSA ( Random Sequential Adsorption) method , according to observed microst ructures.This model can be used to generate a multi2inclusion cell with both randomly dist ributed short -fiber -like and theparticle-like reinforcement s , and that the aspect ratio of short-fiber-like reinforcement s and the dist ribution rule canbe arbit rarily set . While compared with the experimental result s , the simulation result s obtained using this modelare relatively accurate. The result s show that : in the short-fiber-like reinforcement s , the ones parallel to the direc2tion of the applied st ress bear the most st ress , while the ones at an angle of about 45 degrees with the direction ofthe applied st ress bear the least . The particle-like ones bear much less st ress than the short-fiber-like ones parallelto the direction of the applied st ress. The st ress in the mat rix is higher in the local where the reinforcement s arecompact along the direction of the applied st ress.
2006, 23(2): 21-24.
Abstract:
One-dimensional Cu nanowire and Cu/ Al2O3 composite materials were prepared successfully by elect rodeposition. The phase microst ructure and morphology were characterized by SEM , TEM and XRD. There exist oneabsorption belt and no plasm resonance absorption peak in analysis of ult raviolet-visible absorption spect rum. Theabsorption border shif t to the inf rared direction in cont rast to the anodic alumina template is due to the increasing ofdispersion center.
One-dimensional Cu nanowire and Cu/ Al2O3 composite materials were prepared successfully by elect rodeposition. The phase microst ructure and morphology were characterized by SEM , TEM and XRD. There exist oneabsorption belt and no plasm resonance absorption peak in analysis of ult raviolet-visible absorption spect rum. Theabsorption border shif t to the inf rared direction in cont rast to the anodic alumina template is due to the increasing ofdispersion center.
2006, 23(2): 25-29.
Abstract:
In order to eliminate the bubbles during composites manufacturing , a bubble movement visual setup wasbuilt , and the effect s of the resin flow state and flow velocity on the bubble rising velocity were investigated. On thebasis of experimental analysis , a bubble movement model was proposed. The result s demonst rate that the resin flowhas distinct driving effect s on the bubble movement . When the resin and the bubble have the same movement direction , with the increasing of the resin flow velocity , the bubble velocity will increase greatly. When the movementdirection is opposite , the bubble movement velocity will show the decreasing t rend with the increasing of the resinflow velocity. The model is in agreement with the experimental value. These result s will provide the basis for establishing the bubble movement model in the hot-compaction process.
In order to eliminate the bubbles during composites manufacturing , a bubble movement visual setup wasbuilt , and the effect s of the resin flow state and flow velocity on the bubble rising velocity were investigated. On thebasis of experimental analysis , a bubble movement model was proposed. The result s demonst rate that the resin flowhas distinct driving effect s on the bubble movement . When the resin and the bubble have the same movement direction , with the increasing of the resin flow velocity , the bubble velocity will increase greatly. When the movementdirection is opposite , the bubble movement velocity will show the decreasing t rend with the increasing of the resinflow velocity. The model is in agreement with the experimental value. These result s will provide the basis for establishing the bubble movement model in the hot-compaction process.
2006, 23(2): 30-35.
Abstract:
Chromic acid oxidation and sizing agent surface t reatment s were used to modify ult ra high molecularweight polyethylene (U HMWPE) fibers together. The interfacial properties of U HMWPE fiber/ epoxy resin composites were investigated. The result shows that the kinds of resins influence the properties of the composite interface , but the interlaminar shear st rength ( ILSS) of composites is low. Both chromic acid oxidation and sizing agentsurface t reatment s can improve the properties of the composite interface , while the chromic acid oxygen t reatmentweakens the st rength of the fibers if it s t reated time is too long. But the synergy effect s which can improve ILSS ofcomposites obviously without weakening the st rength of the fibers can be achieved by the cooperation of the two different surface t reatment s. This new t reatment is an effective method for surface t reating.
Chromic acid oxidation and sizing agent surface t reatment s were used to modify ult ra high molecularweight polyethylene (U HMWPE) fibers together. The interfacial properties of U HMWPE fiber/ epoxy resin composites were investigated. The result shows that the kinds of resins influence the properties of the composite interface , but the interlaminar shear st rength ( ILSS) of composites is low. Both chromic acid oxidation and sizing agentsurface t reatment s can improve the properties of the composite interface , while the chromic acid oxygen t reatmentweakens the st rength of the fibers if it s t reated time is too long. But the synergy effect s which can improve ILSS ofcomposites obviously without weakening the st rength of the fibers can be achieved by the cooperation of the two different surface t reatment s. This new t reatment is an effective method for surface t reating.
2006, 23(2): 36-41.
Abstract:
The processabilit y and thermal stability of methylol pr opargyl novolac r esins ( MPN resins) were studied, and the mechanical and thermal pr operties of MPN r esins as matr ices of silica laminate composites were character ized. MPN r esins possess excellent processability for RTM and compr ession mold processes, and t he cur ed resinsexhibit a high thermal stability (Tg> 350 e ) . T he silica/MPN laminates show impr oved mechanical pr operties compared to conventional phenolics laminate, and the mechanica l pr operties decrease with increasing methylol contents inMPN resins. T he thermal stability of silica/ MPN laminates ( Tg , 360~ 380 e ) was far superior to t hat of conventional phenolics laminate ( Tg , 280e ) . MPN resins might be utilized as matr ices of advanced thermo-structural composite materials.
The processabilit y and thermal stability of methylol pr opargyl novolac r esins ( MPN resins) were studied, and the mechanical and thermal pr operties of MPN r esins as matr ices of silica laminate composites were character ized. MPN r esins possess excellent processability for RTM and compr ession mold processes, and t he cur ed resinsexhibit a high thermal stability (Tg> 350 e ) . T he silica/MPN laminates show impr oved mechanical pr operties compared to conventional phenolics laminate, and the mechanica l pr operties decrease with increasing methylol contents inMPN resins. T he thermal stability of silica/ MPN laminates ( Tg , 360~ 380 e ) was far superior to t hat of conventional phenolics laminate ( Tg , 280e ) . MPN resins might be utilized as matr ices of advanced thermo-structural composite materials.
2006, 23(2): 42-46.
Abstract:
Some oxygen containing groups such as C —O , C=O and —OH were int roduced onto the molecularchains of linear low-density polyethylene (LLDPE) through ult raviolet irradiation in air without other additives andchemical pollution. These groups content s increase with the ult raviolet irradiation time. Af ter the ult raviolet irradiation , the crystal shape and distance of the crystal plane of LLDPE remain unchanged. However , the melting temperature and crystallinity decrease. Compared with those of LLDPE/ nylon66 (PA66) composites , the dispersion ofirradiated LLDPE in irradiated LLDPE/ PA66 composites and the compatibility between irradiated LLDPE and PA66and interfacial interaction are improved obviously. The mechanical properties of irradiated LLDPE/ PA66 compositesinitially increase and then decrease with increasing the irradiation time. Their maximums are obtained when the irradiation time was 24 h. The tensile st rength , bending st rength and notched impact st rength of irradiated LLDPE for24 h/ PA66 composites increase by about 20 % , 13 % and 330 % compared with those of LLDPE/ PA66 composites ;the irradiated LLDPE shows higher toughening effect .
Some oxygen containing groups such as C —O , C=O and —OH were int roduced onto the molecularchains of linear low-density polyethylene (LLDPE) through ult raviolet irradiation in air without other additives andchemical pollution. These groups content s increase with the ult raviolet irradiation time. Af ter the ult raviolet irradiation , the crystal shape and distance of the crystal plane of LLDPE remain unchanged. However , the melting temperature and crystallinity decrease. Compared with those of LLDPE/ nylon66 (PA66) composites , the dispersion ofirradiated LLDPE in irradiated LLDPE/ PA66 composites and the compatibility between irradiated LLDPE and PA66and interfacial interaction are improved obviously. The mechanical properties of irradiated LLDPE/ PA66 compositesinitially increase and then decrease with increasing the irradiation time. Their maximums are obtained when the irradiation time was 24 h. The tensile st rength , bending st rength and notched impact st rength of irradiated LLDPE for24 h/ PA66 composites increase by about 20 % , 13 % and 330 % compared with those of LLDPE/ PA66 composites ;the irradiated LLDPE shows higher toughening effect .
2006, 23(2): 47-52.
Abstract:
Microwave absorbing properties of the composites containing active carbon-fiber felt screens (ACFFSs)or vertical-arranged carbon fibers (VACFs) were investigated respectively. The results show that the absorbing performances of the composites containing ACFFSs are affected greatly by the patterns (inductive or capacitive) and theelement configurations of ACFFSs. The composite containing the inductive screen obtains a reflection loss below- 10 dB at 8～18 GHz , which is the frequency region of the radar , when the distance between st rip s and the widthof st rip s are 7 mm and 5 mm respectively. The absorption effect of the composites rises with reducing the side ofplates or the distance between plates in the capacitive screen. The space between fibers is critical for the absorbingperformances of the composites containing VACFs. The bandwidth below - 10 dB is 7. 6 GHz when the space is 4mm. By applying the block design method , the composite was divided into four sub-regions which were cent rosymmet rical and contained two inductive screens and two VACF regions. The composite achieves a reflection loss below- 20 dB at 11. 8～18 GHz and the minimum value reaches - 30 dB when the distance between st rip s , the width ofst rips and the space between fibers are 10 mm , 5 mm and 8 mm separately.
Microwave absorbing properties of the composites containing active carbon-fiber felt screens (ACFFSs)or vertical-arranged carbon fibers (VACFs) were investigated respectively. The results show that the absorbing performances of the composites containing ACFFSs are affected greatly by the patterns (inductive or capacitive) and theelement configurations of ACFFSs. The composite containing the inductive screen obtains a reflection loss below- 10 dB at 8～18 GHz , which is the frequency region of the radar , when the distance between st rip s and the widthof st rip s are 7 mm and 5 mm respectively. The absorption effect of the composites rises with reducing the side ofplates or the distance between plates in the capacitive screen. The space between fibers is critical for the absorbingperformances of the composites containing VACFs. The bandwidth below - 10 dB is 7. 6 GHz when the space is 4mm. By applying the block design method , the composite was divided into four sub-regions which were cent rosymmet rical and contained two inductive screens and two VACF regions. The composite achieves a reflection loss below- 20 dB at 11. 8～18 GHz and the minimum value reaches - 30 dB when the distance between st rip s , the width ofst rips and the space between fibers are 10 mm , 5 mm and 8 mm separately.
2006, 23(2): 53-58.
Abstract:
Through the in-si t u polymerization method , a kind of phase change materials microcapsule was preparedby using melamine-urea-formaldehyde resin as the shell material and a phase change material as the core , of whichthe melt point and phase change enthalpy are 24 ℃and 225. 5 J / grespectively. The penet rability and st rength of microcapsule were investigated by altering the mole ratio of urea to melamine. The thermal damage mechanism is thatthe phase change materials leak out f rom the microcapsule when they are heated , and the breakage of the shell wasdue to the thermal expansion of the core and shell materials at high temperature. The damage temperature of the microcapsule shell can be obtained by TGA. The st rength of the shell was evaluated through observing the surfacechange under pressure by mean of scanning elect ron microscopy. The penet rability of the microcapsule was characterized in ethyl alcohol by mean of 752 spect rophotometer. As a result , the average diameter of the microcapsule issmaller than 5μm , and the particle size is cent ralized when the dropping rate of the solidifying solvent is less than018 mL/ min. The mass loss temperature of the microcap sule can be further enhanced up to 30 ℃while the reactionsystem contains 20 % (mass f raction) urea. The microcapsules do not rupture under a pressure of 6. 0 MPa , and thecore material leaks out very slowly from the microcapsule in ethyl alcohol.
Through the in-si t u polymerization method , a kind of phase change materials microcapsule was preparedby using melamine-urea-formaldehyde resin as the shell material and a phase change material as the core , of whichthe melt point and phase change enthalpy are 24 ℃and 225. 5 J / grespectively. The penet rability and st rength of microcapsule were investigated by altering the mole ratio of urea to melamine. The thermal damage mechanism is thatthe phase change materials leak out f rom the microcapsule when they are heated , and the breakage of the shell wasdue to the thermal expansion of the core and shell materials at high temperature. The damage temperature of the microcapsule shell can be obtained by TGA. The st rength of the shell was evaluated through observing the surfacechange under pressure by mean of scanning elect ron microscopy. The penet rability of the microcapsule was characterized in ethyl alcohol by mean of 752 spect rophotometer. As a result , the average diameter of the microcapsule issmaller than 5μm , and the particle size is cent ralized when the dropping rate of the solidifying solvent is less than018 mL/ min. The mass loss temperature of the microcap sule can be further enhanced up to 30 ℃while the reactionsystem contains 20 % (mass f raction) urea. The microcapsules do not rupture under a pressure of 6. 0 MPa , and thecore material leaks out very slowly from the microcapsule in ethyl alcohol.
2006, 23(2): 59-64.
Abstract:
On-axis and off -axis tensile , compress , bend properties of four kinds of different st ructural carbon/epoxy 3D layer -to -layer orthogonal angle interlock woven composites along 0°, 30°, 45°, 60°, 90°directions areevaluated based on a series of experiment and analysis. The result s show that 3D angle interlock woven compositesbelong to the orthogonal anisot ropic material. The st rength-direction and modulus-direction curves of tensile ,compress and bend seem to be maple leaf s , and are characterized by double major axis. There are some differencesbetween these four kinds of different st ructures composites in mechanical anisot ropic properties , and better composites with larger st rength and modulus in the warp direction are the layer -to -layer angle interlock st ructures withstuffer warp , and , by cont rast , better composites with larger st rength and modulus in the weft direction are the layer-to-layer angle interlock st ructures with denser wef t density. It is emphasized that predicted mechanical propertiescan be achieved if fiber kind , fiber size , preform st ructure and yarn density are chosen reasonably.
On-axis and off -axis tensile , compress , bend properties of four kinds of different st ructural carbon/epoxy 3D layer -to -layer orthogonal angle interlock woven composites along 0°, 30°, 45°, 60°, 90°directions areevaluated based on a series of experiment and analysis. The result s show that 3D angle interlock woven compositesbelong to the orthogonal anisot ropic material. The st rength-direction and modulus-direction curves of tensile ,compress and bend seem to be maple leaf s , and are characterized by double major axis. There are some differencesbetween these four kinds of different st ructures composites in mechanical anisot ropic properties , and better composites with larger st rength and modulus in the warp direction are the layer -to -layer angle interlock st ructures withstuffer warp , and , by cont rast , better composites with larger st rength and modulus in the weft direction are the layer-to-layer angle interlock st ructures with denser wef t density. It is emphasized that predicted mechanical propertiescan be achieved if fiber kind , fiber size , preform st ructure and yarn density are chosen reasonably.
2006, 23(2): 65-70.
Abstract:
The preparation , microst ructure , compressive properties and thermal stability of the glass bead reinforced rigid polyurethane foams ( PUR/ GB) are studied. When the content of the glass bead reaches 10 % , the compressive st rength and compressive modulus of PUR/ GBs reach their maximum , respectively. When glass beads arepret reated with silicane coupling agent , the compressive st rength and compressive modulus improve to a large extent ; the onset decomposition temperature and peak temperature improve to some extent . Analyses by SEM , XPSand EDS reveal that the f roth density of PUR/ GB increases , frothy diameter decreases , the interfacial adhesion between the surface of glass bead and PUR mat rix is good , and glass beads disperse homogeneously in PUR mat rix.These are the reason why compressive properties and thermal stability are enhanced largely.
The preparation , microst ructure , compressive properties and thermal stability of the glass bead reinforced rigid polyurethane foams ( PUR/ GB) are studied. When the content of the glass bead reaches 10 % , the compressive st rength and compressive modulus of PUR/ GBs reach their maximum , respectively. When glass beads arepret reated with silicane coupling agent , the compressive st rength and compressive modulus improve to a large extent ; the onset decomposition temperature and peak temperature improve to some extent . Analyses by SEM , XPSand EDS reveal that the f roth density of PUR/ GB increases , frothy diameter decreases , the interfacial adhesion between the surface of glass bead and PUR mat rix is good , and glass beads disperse homogeneously in PUR mat rix.These are the reason why compressive properties and thermal stability are enhanced largely.
2006, 23(2): 71-76.
Abstract:
Polypropylene ( PP) composites with polybutyl acrylate (PBA) in-si tu graf ted nano-silica were preparedby a conventional melt compounding technique. The mechanism of the graf t polymerization and the st ructure of thenanocomposites were studied by means of Haake torque rheometer , inf rared spect roscopy , thermogravimet ry , X-rayphotoelect ron spect roscopy , transmission elect ron microscopy , etc. It is proved that PBA has been chemically bonded to the surface of nano-silica during the in2si tu melt graf t polymerization. The modified nano-silica particles arehomogeneously dispersed in PP mat rix and a st rong interfacial interaction is established by the chain entanglementbetween the graf ted polymer and the mat rix.
Polypropylene ( PP) composites with polybutyl acrylate (PBA) in-si tu graf ted nano-silica were preparedby a conventional melt compounding technique. The mechanism of the graf t polymerization and the st ructure of thenanocomposites were studied by means of Haake torque rheometer , inf rared spect roscopy , thermogravimet ry , X-rayphotoelect ron spect roscopy , transmission elect ron microscopy , etc. It is proved that PBA has been chemically bonded to the surface of nano-silica during the in2si tu melt graf t polymerization. The modified nano-silica particles arehomogeneously dispersed in PP mat rix and a st rong interfacial interaction is established by the chain entanglementbetween the graf ted polymer and the mat rix.
2006, 23(2): 77-81.
Abstract:
The vermiculite was intercalated quickly with hexadecylt rimethylammonium bromide through milling.The natural rubber and the organic vermiculite nanocomposites were prepared , af ter mixing in a HA KKE mixer.The microst ructures and properties of nanocomposities were characterized by means of XRD , SEM , DMA and DSC.The silicate layer was exfoliated in the NR mat rix af ter curing of the nanocomposites. The mechanical test s show theperformances of nanocomposites , such as tensile st rength , elongation at break , st ress at 300 % elongation , tearst rength and hardness (Shore A) are improved prominently. The nanocomposite with 15wt % organic vermiculitehas higher modulus , and it s glass2t ransition temperature is unchanged.
The vermiculite was intercalated quickly with hexadecylt rimethylammonium bromide through milling.The natural rubber and the organic vermiculite nanocomposites were prepared , af ter mixing in a HA KKE mixer.The microst ructures and properties of nanocomposities were characterized by means of XRD , SEM , DMA and DSC.The silicate layer was exfoliated in the NR mat rix af ter curing of the nanocomposites. The mechanical test s show theperformances of nanocomposites , such as tensile st rength , elongation at break , st ress at 300 % elongation , tearst rength and hardness (Shore A) are improved prominently. The nanocomposite with 15wt % organic vermiculitehas higher modulus , and it s glass2t ransition temperature is unchanged.
2006, 23(2): 82-87.
Abstract:
Upon being subjected to the external load , acoustic emission (AE) may occur f rom mat rix cracking , interface debonding , fiber f racture , etc in composite materials. U HMWPE/ HDPE composite materials were experimented to determine the event amplitude content of AE signals under tensile loads. Special specimens , designed tofail under well-defined modes such as mat rix plastic deformation and cracking , fiber-mat rix debonding , fiber breakage , delamination , etc were tested under the loads f rom zero to failure. The f racture surfaces of the specimens wereobserved by a scanning elect ron microscope ( SEM) . The AE signals were distinguished as being released fromseveral special types of damage. AE measurement s were performed subsequently for different types of U HMWPE/HDPE quasi-isot ropic laminates under the same loading conditions. The correlations are established between thedamage modes and acoustic emission event s amplitude of special specimens which exhibit the dominant damage mechanisms. The AE characteristics of damage growth processes and the fracture mechanisms in U HMWPE/ HDPEquasi2isot ropic laminates are revealed. Accumulative numbers of acoustic emission event s for different types ofU HMWPE/ HDPE quasi-isot ropic laminates vs tensile st ress curves are different from each other ; the correspondingloading levels of their same type of damage occurrence are not equal. The results show that ply stacking angles andsequences affect remarkably the damage growth process of these laminates. It is verified that the final fracture ofthese materials is caused by severe interlaminar delamination.
Upon being subjected to the external load , acoustic emission (AE) may occur f rom mat rix cracking , interface debonding , fiber f racture , etc in composite materials. U HMWPE/ HDPE composite materials were experimented to determine the event amplitude content of AE signals under tensile loads. Special specimens , designed tofail under well-defined modes such as mat rix plastic deformation and cracking , fiber-mat rix debonding , fiber breakage , delamination , etc were tested under the loads f rom zero to failure. The f racture surfaces of the specimens wereobserved by a scanning elect ron microscope ( SEM) . The AE signals were distinguished as being released fromseveral special types of damage. AE measurement s were performed subsequently for different types of U HMWPE/HDPE quasi-isot ropic laminates under the same loading conditions. The correlations are established between thedamage modes and acoustic emission event s amplitude of special specimens which exhibit the dominant damage mechanisms. The AE characteristics of damage growth processes and the fracture mechanisms in U HMWPE/ HDPEquasi2isot ropic laminates are revealed. Accumulative numbers of acoustic emission event s for different types ofU HMWPE/ HDPE quasi-isot ropic laminates vs tensile st ress curves are different from each other ; the correspondingloading levels of their same type of damage occurrence are not equal. The results show that ply stacking angles andsequences affect remarkably the damage growth process of these laminates. It is verified that the final fracture ofthese materials is caused by severe interlaminar delamination.
2006, 23(2): 88-92.
Abstract:
On the basis of template and elect roless methods , NiCo/ PTFE magnetic composite membranes were prepared with N2H4 as reducing agent . The paper studied the optimum preparation conditions and characterized st ructures and magnetic properties of the membranes by DSC , SEM , XRD , VSM. The result s show that magnetic composite membranes with susceptibility of 0. 16 cm3 / g have ferromagnetic property (Ms = 83. 38 Am2 / kg , Mr = 29. 31Am2 / kg , Hc = 111. 47 Oe) , which are obtained f rom solution of 0. 14 mol/ L Co2+ , 0. 06 mol/ L Ni2+ , 1. 00 mol/ LNaOH , 0140 mol/ L N2H4 at 70 ℃and 70 min. Magnetic Ni and Co particles appear in the pores and on the surfaceof PTFE membranes , and no chemical bonds are found between magnetic particles and membranes. The compositemembranes have int rinsic properties of sof t magnetic material.
On the basis of template and elect roless methods , NiCo/ PTFE magnetic composite membranes were prepared with N2H4 as reducing agent . The paper studied the optimum preparation conditions and characterized st ructures and magnetic properties of the membranes by DSC , SEM , XRD , VSM. The result s show that magnetic composite membranes with susceptibility of 0. 16 cm3 / g have ferromagnetic property (Ms = 83. 38 Am2 / kg , Mr = 29. 31Am2 / kg , Hc = 111. 47 Oe) , which are obtained f rom solution of 0. 14 mol/ L Co2+ , 0. 06 mol/ L Ni2+ , 1. 00 mol/ LNaOH , 0140 mol/ L N2H4 at 70 ℃and 70 min. Magnetic Ni and Co particles appear in the pores and on the surfaceof PTFE membranes , and no chemical bonds are found between magnetic particles and membranes. The compositemembranes have int rinsic properties of sof t magnetic material.
2006, 23(2): 93-98.
Abstract:
A new theoretical model of the hybrid composite rebar is proposed to counter the disadvantages such aslow elastic modulus , low elongation af ter break and high cost of current composite rebars. The glass compositerebars and hybrid composite rebars were fabricated. The single axial tensile behavior and accelerating corrosionproperties were tested and analyzed. The result s show that the tensile modulus of the new hybrid rebar is 142 GPa.Compared with the glass composite rebar , the new hybrid composite rebars possess the characteristics of corrosionresistance , good ductility and low cost .
A new theoretical model of the hybrid composite rebar is proposed to counter the disadvantages such aslow elastic modulus , low elongation af ter break and high cost of current composite rebars. The glass compositerebars and hybrid composite rebars were fabricated. The single axial tensile behavior and accelerating corrosionproperties were tested and analyzed. The result s show that the tensile modulus of the new hybrid rebar is 142 GPa.Compared with the glass composite rebar , the new hybrid composite rebars possess the characteristics of corrosionresistance , good ductility and low cost .
2006, 23(2): 99-103.
Abstract:
Monolithic mesoporous silica was prepared by a sol-gel technique. The ZnS/ SiO2 assembly systems withdifferent ZnS loading (0. 05 , 0. 1 , 0. 2 and 0. 5 mol/ L) were obtained by immersing , followed by drying and thermalreaction. It was found that the optical absorption edges and the peaks of fluorescence spect rum have a red2shif t withincreasing the ZnS loading concent ration. The photoluminescence intensity of samples is enhanced along with theincrease of the annealing temperature and slows down for the samples annealed at temperature above 450 ℃. Thecalculated result shows that the size of ZnS particles in the mesoporous SiO2 is similar to it s exciton radius in magnitude. The shif t of the absorption edge is att ributed to the quantum size effect .
Monolithic mesoporous silica was prepared by a sol-gel technique. The ZnS/ SiO2 assembly systems withdifferent ZnS loading (0. 05 , 0. 1 , 0. 2 and 0. 5 mol/ L) were obtained by immersing , followed by drying and thermalreaction. It was found that the optical absorption edges and the peaks of fluorescence spect rum have a red2shif t withincreasing the ZnS loading concent ration. The photoluminescence intensity of samples is enhanced along with theincrease of the annealing temperature and slows down for the samples annealed at temperature above 450 ℃. Thecalculated result shows that the size of ZnS particles in the mesoporous SiO2 is similar to it s exciton radius in magnitude. The shif t of the absorption edge is att ributed to the quantum size effect .
2006, 23(2): 104-109.
Abstract:
The diluent s ( Al2O3 , Cr2O3 ) and reactive additive ( MoO3 ) were added to Al-Cr2O3 system.Al (Cr) 2O3-Cr (Mo) ceramic mat rix composites with eutectic mixture of fine rod metal phase were successfully fabri2cated by means of the thermal explosive combustion synthesis method. The effect s of the reactive system composi2tion and preparation process on the microst ructure of the composites were investigated. The product s with about 90percent relative density were obtained at a pressure of 1. 26 MPa on the synthesized material melt . The ceramicphase has three morphologies , block grains with round edges , fine rectangular slab grains with different orientationsand coarse rectangular slab grains. Metal particles dist ribute int ragranularly or intergranularly in the ceramic crystalgrains , or eutectic st ructure forms. The eutectic mixture has a quasi2regular st ructure. The fine rod metal phasedisperses in the continued ceramic mat rix. The eutectic mixture is regionally dist ributed throughout the specimen.The microst ructures of the fabricated composites are principally characterized by in si tu rectangular slab ceramicgrains and the rod eutectic mixture.
The diluent s ( Al2O3 , Cr2O3 ) and reactive additive ( MoO3 ) were added to Al-Cr2O3 system.Al (Cr) 2O3-Cr (Mo) ceramic mat rix composites with eutectic mixture of fine rod metal phase were successfully fabri2cated by means of the thermal explosive combustion synthesis method. The effect s of the reactive system composi2tion and preparation process on the microst ructure of the composites were investigated. The product s with about 90percent relative density were obtained at a pressure of 1. 26 MPa on the synthesized material melt . The ceramicphase has three morphologies , block grains with round edges , fine rectangular slab grains with different orientationsand coarse rectangular slab grains. Metal particles dist ribute int ragranularly or intergranularly in the ceramic crystalgrains , or eutectic st ructure forms. The eutectic mixture has a quasi2regular st ructure. The fine rod metal phasedisperses in the continued ceramic mat rix. The eutectic mixture is regionally dist ributed throughout the specimen.The microst ructures of the fabricated composites are principally characterized by in si tu rectangular slab ceramicgrains and the rod eutectic mixture.
2006, 23(2): 110-114.
Abstract:
The R-curve behavior of SiC/ BN multilayered ceramics with different component s in the weak layer wasevaluated using the indentation-st rength-in-bending technique. The influence of the component s of the weak layer onthe R-curve of the SiC/ BN multilayered ceramics was studied. The results show that a rising R-curve behavior isdemonst rated for the laminated SiC/ BN ceramics , and varies with the component s of the weak layer. The SiC/ BNmultilayered ceramic with 30 % Al2O3 addition in the weak layer has a steepest rising R-curve. The above result s areatt ributed to their different toughening mechanisms and interfacial coherent states. I n-si tu toughening is the maintoughening mechanism for the monolithic SiC ceramics , while crack deflection , crack branching and crack delaminating at the SiC/ BN weak interfaces for SiC/ BN multilayered ceramics. The component s in the weak layer have animportant effect on the crack deflection. The interface with a right coherent st ress cont ributes to the crack deflection , and the interface with too weak or very st rong coherent stress does harm to the crack deflection.
The R-curve behavior of SiC/ BN multilayered ceramics with different component s in the weak layer wasevaluated using the indentation-st rength-in-bending technique. The influence of the component s of the weak layer onthe R-curve of the SiC/ BN multilayered ceramics was studied. The results show that a rising R-curve behavior isdemonst rated for the laminated SiC/ BN ceramics , and varies with the component s of the weak layer. The SiC/ BNmultilayered ceramic with 30 % Al2O3 addition in the weak layer has a steepest rising R-curve. The above result s areatt ributed to their different toughening mechanisms and interfacial coherent states. I n-si tu toughening is the maintoughening mechanism for the monolithic SiC ceramics , while crack deflection , crack branching and crack delaminating at the SiC/ BN weak interfaces for SiC/ BN multilayered ceramics. The component s in the weak layer have animportant effect on the crack deflection. The interface with a right coherent st ress cont ributes to the crack deflection , and the interface with too weak or very st rong coherent stress does harm to the crack deflection.
2006, 23(2): 115-122.
Abstract:
The preparation , microst ructure and biocompatibility were studied for the hydroxylapatite-zirconia( HA/ ZrO2 ) biocomposite applied to artificial implant s of human load-bearing part s. XRD , SEM and TEM wereused to analyse the powders and composite. In order to evaluate the immunocompatibility of the composite , it sext ract was picked up to activate the peripheral blood mononuclear cells ( PBMCs) donated by healthy young peoplein vit ro. The result s show that the major phases of the compositeps surface layer areβ- andα-tricalcium phosphate (β- ,α-TCP) and CaZrO3 af ter being sintered at 1600 ℃for 3 hours. The surface roughness of the simplicial compositeand graded composite is 3. 12μm and 1. 95μm respectively. Their tensile st rength is 732. 85 MPa and 689. 04 MParespectively. The composite has immunocompatibility , whereas the immunocompatibility of the graded composite isbetter than that of the simplicial composite.
The preparation , microst ructure and biocompatibility were studied for the hydroxylapatite-zirconia( HA/ ZrO2 ) biocomposite applied to artificial implant s of human load-bearing part s. XRD , SEM and TEM wereused to analyse the powders and composite. In order to evaluate the immunocompatibility of the composite , it sext ract was picked up to activate the peripheral blood mononuclear cells ( PBMCs) donated by healthy young peoplein vit ro. The result s show that the major phases of the compositeps surface layer areβ- andα-tricalcium phosphate (β- ,α-TCP) and CaZrO3 af ter being sintered at 1600 ℃for 3 hours. The surface roughness of the simplicial compositeand graded composite is 3. 12μm and 1. 95μm respectively. Their tensile st rength is 732. 85 MPa and 689. 04 MParespectively. The composite has immunocompatibility , whereas the immunocompatibility of the graded composite isbetter than that of the simplicial composite.
2006, 23(2): 123-127.
Abstract:
The pulse -echo technique was used to obtain the ult rasonic measurement of two different group s ofcarbon fiber reinforced plastic (CFRP) samples , and FFT algorithm was used for f requency spect ral analysis. Theattenuation coefficient shows approximately linear behaviour with f requency over the frequency range used , and theattenuation slope increases with the void content . The attenuation effect s of voids were shown by the dropped amplitude , the downshif ted position and the decreased bandwidth of the center peak. The results indicate that linearrelationships hold between the cent roid f requency shift , the at tenuation slope and the void content , and theserelationships will aid the model development for void content detection using frequency spect ralanalysis.
The pulse -echo technique was used to obtain the ult rasonic measurement of two different group s ofcarbon fiber reinforced plastic (CFRP) samples , and FFT algorithm was used for f requency spect ral analysis. Theattenuation coefficient shows approximately linear behaviour with f requency over the frequency range used , and theattenuation slope increases with the void content . The attenuation effect s of voids were shown by the dropped amplitude , the downshif ted position and the decreased bandwidth of the center peak. The results indicate that linearrelationships hold between the cent roid f requency shift , the at tenuation slope and the void content , and theserelationships will aid the model development for void content detection using frequency spect ralanalysis.
2006, 23(2): 128-132.
Abstract:
The sound t ransmission behaviors through a thin elect rorheological ( ER) layer sandwiched between twosheet s of flexible elect rodes were investigated experimentally. The t ransmission spect rum of the ER layer shows frequency selective characters. The relative t ransmittance T of the ER layer with a particle volume fraction of 31 %exhibit s an enhanced hump within 100～160 Hz with the increase of the external elect ric field E , while T doesnptchange with E at other f requencies. The relative t ransmittance T at the hump peak of 130 Hz under E = 2. 0 kV/ mmis nearly 7 times that of zero elect ric field st rength. The phase angle of t ransmitted sound increases with E also. Atthe f requency of 105 Hz , the long axis of Lisajous ellipse figure rotates clockwise by 45°as E increases f rom 0 tO2. 0 kV/ mm. With the increase in E , the amplitude and phase of the t ransmission hump show tunable features. Asφincreases f rom 16 % to 31 % , the maximum T changes f rom 1. 8 to 7 ( E = 2. 0 kV/ mm) and the respondingf requency band of the enhanced hump moves towards the high f requency direction. The interaction between the fieldinduced microst ructures and the sound waves may be the cause of the phenomenon.
The sound t ransmission behaviors through a thin elect rorheological ( ER) layer sandwiched between twosheet s of flexible elect rodes were investigated experimentally. The t ransmission spect rum of the ER layer shows frequency selective characters. The relative t ransmittance T of the ER layer with a particle volume fraction of 31 %exhibit s an enhanced hump within 100～160 Hz with the increase of the external elect ric field E , while T doesnptchange with E at other f requencies. The relative t ransmittance T at the hump peak of 130 Hz under E = 2. 0 kV/ mmis nearly 7 times that of zero elect ric field st rength. The phase angle of t ransmitted sound increases with E also. Atthe f requency of 105 Hz , the long axis of Lisajous ellipse figure rotates clockwise by 45°as E increases f rom 0 tO2. 0 kV/ mm. With the increase in E , the amplitude and phase of the t ransmission hump show tunable features. Asφincreases f rom 16 % to 31 % , the maximum T changes f rom 1. 8 to 7 ( E = 2. 0 kV/ mm) and the respondingf requency band of the enhanced hump moves towards the high f requency direction. The interaction between the fieldinduced microst ructures and the sound waves may be the cause of the phenomenon.
2006, 23(2): 133-142.
Abstract:
By virtue of the nearest surface function formula , this cont ribution gives a quantitative formula to calculate the volume f raction of interface in concrete. A random point sampling approach was used to verify the feasibilityof the aforementioned formula. In addition , for the concrete in which the aggregate follows the Fuller dist ributionfunction , this formula was employed to elucidate the variation of the ITZ volume f raction with the aggregate volumef raction at various ITZ thicknesses. The analytical formulas were further derived to illuminate the different effect son volume f raction of ITZ among ITZ thickness , volume f raction of aggregate , and particle size dist ribution of aggregate. Both qualitative and quantitative approaches were put forward to evaluate the overlapping degree betweenneighboring ITZs. The result s indicate that for the concrete with common-used range of aggregate volume f raction ,the influencing order of these three factors on the ITZ volume f raction as well as on the overlapping degree of neighboring ITZs is : ITZ thickness > volume f raction of aggregate > fineness of aggregate.
By virtue of the nearest surface function formula , this cont ribution gives a quantitative formula to calculate the volume f raction of interface in concrete. A random point sampling approach was used to verify the feasibilityof the aforementioned formula. In addition , for the concrete in which the aggregate follows the Fuller dist ributionfunction , this formula was employed to elucidate the variation of the ITZ volume f raction with the aggregate volumef raction at various ITZ thicknesses. The analytical formulas were further derived to illuminate the different effect son volume f raction of ITZ among ITZ thickness , volume f raction of aggregate , and particle size dist ribution of aggregate. Both qualitative and quantitative approaches were put forward to evaluate the overlapping degree betweenneighboring ITZs. The result s indicate that for the concrete with common-used range of aggregate volume f raction ,the influencing order of these three factors on the ITZ volume f raction as well as on the overlapping degree of neighboring ITZs is : ITZ thickness > volume f raction of aggregate > fineness of aggregate.
2006, 23(2): 143-149.
Abstract:
According to the analysis of deformation and damage model of FRC laminates after ballistic impact , atwo phase theoretical penet ration model was presented , based on the impulsive dynamics and st ress wave propagation analysis , which includes a shear penet ration phase and the consecutive penet ration phase. The transient t rapezium deformation cone model was int roduced firstly in this article , and the interaction between projectile and targetin the consecutive penet ration phase was discussed by this model. The calculation code by V2Fort ran was compiledand the calculation result s were perfect compared with experimental result s. When the initial velocity is 300 ～900 m/ s , the difference is less than 50 m/ s. The emergence and come-into-being mechanisms of some experimentalphenomena , such as t rapezium deformation cone , petal breakage on back face and the difference in the damage modelbetween FRCps f ront and back faces , have been made clear now , and some new ways and rules , which can be infavor of improving ballistic resistance capability of FRC , are put forward , such as : reduce the content of mat rix andthe interlaminate st rength or increase the shearing resistance of f ront layers , etc.
According to the analysis of deformation and damage model of FRC laminates after ballistic impact , atwo phase theoretical penet ration model was presented , based on the impulsive dynamics and st ress wave propagation analysis , which includes a shear penet ration phase and the consecutive penet ration phase. The transient t rapezium deformation cone model was int roduced firstly in this article , and the interaction between projectile and targetin the consecutive penet ration phase was discussed by this model. The calculation code by V2Fort ran was compiledand the calculation result s were perfect compared with experimental result s. When the initial velocity is 300 ～900 m/ s , the difference is less than 50 m/ s. The emergence and come-into-being mechanisms of some experimentalphenomena , such as t rapezium deformation cone , petal breakage on back face and the difference in the damage modelbetween FRCps f ront and back faces , have been made clear now , and some new ways and rules , which can be infavor of improving ballistic resistance capability of FRC , are put forward , such as : reduce the content of mat rix andthe interlaminate st rength or increase the shearing resistance of f ront layers , etc.
2006, 23(2): 150-157.
Abstract:
A reliable computational procedur e was established for simulating the laminate fa ilure. Employing ast rain-based failur e criterion, it was modif ied from H ashin failur e cr iterion as well as the concept of progressive stiffness degr adation to model the intr alaminar failure. An appr oach to predict the initiation and propagation of interlaminar damage ( delamination) is brought forwar d based on the contact constr aint introduced by the penalty functionmet hod: a scalar damage variable is intr oduced and the degradation of the interface st iffness is established and adamage sur face which combines st ress-based and f racture-mechanics-based failure cr iter ia is set up to derive the damage evolut ion law. Both the intr alaminar and int erlaminar models are implement ed into a commercial finit e elementcode, ABAQUS/ Explicit, via it s user subroutines respectively. Numer ical prediction is carr ied out on carbon-epoxylaminate plates due to tr ansver sely low velocit y impact. Good agr eement between exper imental results and numericalresults is obtained.
A reliable computational procedur e was established for simulating the laminate fa ilure. Employing ast rain-based failur e criterion, it was modif ied from H ashin failur e cr iterion as well as the concept of progressive stiffness degr adation to model the intr alaminar failure. An appr oach to predict the initiation and propagation of interlaminar damage ( delamination) is brought forwar d based on the contact constr aint introduced by the penalty functionmet hod: a scalar damage variable is intr oduced and the degradation of the interface st iffness is established and adamage sur face which combines st ress-based and f racture-mechanics-based failure cr iter ia is set up to derive the damage evolut ion law. Both the intr alaminar and int erlaminar models are implement ed into a commercial finit e elementcode, ABAQUS/ Explicit, via it s user subroutines respectively. Numer ical prediction is carr ied out on carbon-epoxylaminate plates due to tr ansver sely low velocit y impact. Good agr eement between exper imental results and numericalresults is obtained.
2006, 23(2): 158-162.
Abstract:
The cantilever beam-plate with discontinuity in thickness is considered as a laminated plate. Based on thesemi-analytical solution for Hamilton canonical equation , the linear equation of each layer is established separately.The compatibility of displacement s and st resses on the interface between layers is employed to derive the integralequation and the characteristic equation. The main advantages are there is no rest riction on the thickness of the cantilever beam-plate and the present method can deal with the cantilever laminated plate with discontinuity and dissymmet ry in thickness. The method can also be modified to analyze the corresponding problems of stiffened shells , stiffened piezolaminated plates , and plates or shells with piezoelect ric sensor and actuator patches.
The cantilever beam-plate with discontinuity in thickness is considered as a laminated plate. Based on thesemi-analytical solution for Hamilton canonical equation , the linear equation of each layer is established separately.The compatibility of displacement s and st resses on the interface between layers is employed to derive the integralequation and the characteristic equation. The main advantages are there is no rest riction on the thickness of the cantilever beam-plate and the present method can deal with the cantilever laminated plate with discontinuity and dissymmet ry in thickness. The method can also be modified to analyze the corresponding problems of stiffened shells , stiffened piezolaminated plates , and plates or shells with piezoelect ric sensor and actuator patches.
2006, 23(2): 163-168.
Abstract:
A three-dimensional non-linear progressive damage model was developed to predict the response of composite laminates with a single bolt . The analysis took into account the contact at the bolt-hole interface by Augmented Lagrangian Contact Algorithm. The objectives of the study were to investigate the onset and development of thefibre damage , mat rix damage , fibre-mat rix shear , and their relationship. From the load-displacement curves drawnfrom the calculation , the initial bearing damage strength was predicted. The effect s of stacking sequences and geomet rical parameters on the bearing st rength were determined experimentally. Good agreement between experimentalresult s and numerical predictions is observed.
A three-dimensional non-linear progressive damage model was developed to predict the response of composite laminates with a single bolt . The analysis took into account the contact at the bolt-hole interface by Augmented Lagrangian Contact Algorithm. The objectives of the study were to investigate the onset and development of thefibre damage , mat rix damage , fibre-mat rix shear , and their relationship. From the load-displacement curves drawnfrom the calculation , the initial bearing damage strength was predicted. The effect s of stacking sequences and geomet rical parameters on the bearing st rength were determined experimentally. Good agreement between experimentalresult s and numerical predictions is observed.
2006, 23(2): 169-174.
Abstract:
Based on the shear flexible theory , a finite element model was developed to take into account the quadratic warping effect of arbit rary cross-sections of spatial thin-walled composite beams , taking the 9-node plane element to simulate an arbit rary beam cross-section and the 27-node solid element to simulate the quadratic out-of-planewarping displacement . According to the model obtained in this paper , the interrelated spatial composite beams calculating program was written out . The numerical examples show that the analytical model derived in the paper is correct , which can be used in the analysis of complex spatial thin2walled composite beams under several coupling loads.
Based on the shear flexible theory , a finite element model was developed to take into account the quadratic warping effect of arbit rary cross-sections of spatial thin-walled composite beams , taking the 9-node plane element to simulate an arbit rary beam cross-section and the 27-node solid element to simulate the quadratic out-of-planewarping displacement . According to the model obtained in this paper , the interrelated spatial composite beams calculating program was written out . The numerical examples show that the analytical model derived in the paper is correct , which can be used in the analysis of complex spatial thin2walled composite beams under several coupling loads.
2006, 23(2): 175-179.
Abstract:
Based on the thermal conduct theory and cure kinetics , the history of cure temperature and degree ofcure was investigated for the orthot ropic laminate during curing. The temperature and degree of cure were chosen astwo additional degrees of nodes in FEM models , and the coupling of them was taken into account . The result showsthat : for the thick laminate , the peak value of the temperature was increased , and the initiation of the crosslinkingreaction at the center point was late ; for the laminates with different fiber content s , the development of the degree ofcure is synchronic at the early stage of the curing process , when the temperature is higher than that of the dwell(85 ℃) , the lower the fiber content in the laminates , the higher the peak value of temperature at the center of thelaminates , and it s corresponding time is quicker.
Based on the thermal conduct theory and cure kinetics , the history of cure temperature and degree ofcure was investigated for the orthot ropic laminate during curing. The temperature and degree of cure were chosen astwo additional degrees of nodes in FEM models , and the coupling of them was taken into account . The result showsthat : for the thick laminate , the peak value of the temperature was increased , and the initiation of the crosslinkingreaction at the center point was late ; for the laminates with different fiber content s , the development of the degree ofcure is synchronic at the early stage of the curing process , when the temperature is higher than that of the dwell(85 ℃) , the lower the fiber content in the laminates , the higher the peak value of temperature at the center of thelaminates , and it s corresponding time is quicker.
2006, 23(2): 180-184.
Abstract:
Computer simulation of the low-velocity impact process of the composite laminate with prefabricateddefect was performed to demonst rate the impact process and damage progress in detail. A finite element programwritten in FORTRAN was developed to analyze the t ransient dynamic response of composite plates. The Hertziancontact law was modified in order to accommodate the serious damage in the plate. The Wilson-scheme was adoptedto perform time integration for the motion equations of the impactor and composite plate system. The Lagrange multiplier method was used to deal with dynamic contact problems. The result s of computer simulation including theforce history and delamination areas were found to correlate well with the experiment s. The experiment and calculationresults show that the delamination defects in the laminates have the effect that prevents the propagation of delamination.
Computer simulation of the low-velocity impact process of the composite laminate with prefabricateddefect was performed to demonst rate the impact process and damage progress in detail. A finite element programwritten in FORTRAN was developed to analyze the t ransient dynamic response of composite plates. The Hertziancontact law was modified in order to accommodate the serious damage in the plate. The Wilson-scheme was adoptedto perform time integration for the motion equations of the impactor and composite plate system. The Lagrange multiplier method was used to deal with dynamic contact problems. The result s of computer simulation including theforce history and delamination areas were found to correlate well with the experiment s. The experiment and calculationresults show that the delamination defects in the laminates have the effect that prevents the propagation of delamination.
