1997 Vol. 14, No. 1
1997, 14(1): 1-5.
Abstract:
A brand-new methodl for increasing toughness and raising hydrothermal resistance ability of CFRP(carbon fiber reinforced plastic)was reported in this paper. This method is to treat and polymerize the graft modification surface of the carbon fiber and introduce a plastic and water-proof hybrid interphase into CFRP by cold plasma,so that the toughness of CFRP was increased by 148% and the fracture process of CFRP was transited from brittle fracture into tough fracture. The modulus,ILSs,Tg and relaxation activity energy of CFRP were not decreased but increased. The hydrothermal resistance ability of CFRP was improved very much and the retention ratio of ILSS was raised from 92.73% to 99.79% after 8 h in boiling water.
A brand-new methodl for increasing toughness and raising hydrothermal resistance ability of CFRP(carbon fiber reinforced plastic)was reported in this paper. This method is to treat and polymerize the graft modification surface of the carbon fiber and introduce a plastic and water-proof hybrid interphase into CFRP by cold plasma,so that the toughness of CFRP was increased by 148% and the fracture process of CFRP was transited from brittle fracture into tough fracture. The modulus,ILSs,Tg and relaxation activity energy of CFRP were not decreased but increased. The hydrothermal resistance ability of CFRP was improved very much and the retention ratio of ILSS was raised from 92.73% to 99.79% after 8 h in boiling water.
1997, 14(1): 6-11.
Abstract:
Based on rheological and morphological examinations,the formation behavior and the fibrillation conditions of a thermotropic liquid crystalline polymer as a dispersed phase in a thermoplastic matrix have been studied using models by Taylor,Cox and Grace. The fibrillation development has been characterized by We-number.viscosity ratio and critical burst time. The resuits show satisfactory agreement between the theoretical calculations and the experimental determmations.
Based on rheological and morphological examinations,the formation behavior and the fibrillation conditions of a thermotropic liquid crystalline polymer as a dispersed phase in a thermoplastic matrix have been studied using models by Taylor,Cox and Grace. The fibrillation development has been characterized by We-number.viscosity ratio and critical burst time. The resuits show satisfactory agreement between the theoretical calculations and the experimental determmations.
1997, 14(1): 12-14.
Abstract:
The PZT/epoxy and PZT/nylon 0-3 composites were made. It shows that with the same piezoelectric phase.the saturation poling field Es and poling time ts for composites whose matrix is nylon PA-1010 are lower than those of composites whose matrix is epoxy resin E-20,but d3333 of the former composites is higher than that of the latter composites.
The PZT/epoxy and PZT/nylon 0-3 composites were made. It shows that with the same piezoelectric phase.the saturation poling field Es and poling time ts for composites whose matrix is nylon PA-1010 are lower than those of composites whose matrix is epoxy resin E-20,but d3333 of the former composites is higher than that of the latter composites.
1997, 14(1): 15-21.
Abstract:
Using low cost Al2O3-SiO2 fibre as reinforced phase.ZL108 alloy composites were made by squeeze casting. The composites and ZL108 alloy were accelerated ageing at different temperatures.and then examined by compression test. The analysis from DSC,EPMA and TEM suggests that the reason why after the accelerated ageing at 488K for 30min (T6).the compression proof stress of the composite with 20 Vf% fibre below 573K was lower than that of ZL108 alloy is the reaction of Mg in the matrix and Al2O3-SiO2 fibre,which formed MgAl2O4, consumed lot of Mg in the matrix.and led to the poor ageing hardness and low compression proof stress. It is proposed that after annealing at 623K for 720 hours,the compression proof stress of the composite being much higher than that of ZL108 alloy is because ZL108 alloy produced over ageing at these temperatures. Therefore the effect of fibre reinforcement on the tomposite was significant. At high temperature of 673K.the proof stress of the composite with 20 Vf% fibre was about twice as high as that of ZL108 alloy. At all temperatures,the proof stress of composite with 5 Vf% fibre is lower than that of composite with 20 Vf%.
Using low cost Al2O3-SiO2 fibre as reinforced phase.ZL108 alloy composites were made by squeeze casting. The composites and ZL108 alloy were accelerated ageing at different temperatures.and then examined by compression test. The analysis from DSC,EPMA and TEM suggests that the reason why after the accelerated ageing at 488K for 30min (T6).the compression proof stress of the composite with 20 Vf% fibre below 573K was lower than that of ZL108 alloy is the reaction of Mg in the matrix and Al2O3-SiO2 fibre,which formed MgAl2O4, consumed lot of Mg in the matrix.and led to the poor ageing hardness and low compression proof stress. It is proposed that after annealing at 623K for 720 hours,the compression proof stress of the composite being much higher than that of ZL108 alloy is because ZL108 alloy produced over ageing at these temperatures. Therefore the effect of fibre reinforcement on the tomposite was significant. At high temperature of 673K.the proof stress of the composite with 20 Vf% fibre was about twice as high as that of ZL108 alloy. At all temperatures,the proof stress of composite with 5 Vf% fibre is lower than that of composite with 20 Vf%.
1997, 14(1): 22-26.
Abstract:
Abstract The study on the mechanism of reactive processing for the fabrication of α-Al2O3p/Al composite was performed by pressureless metal infiltration technique,optical micrography,SEM-micrography and EDS-analysis and thermodynamic consideration. This suggests the mechanism of reactive processing:the atmosphere of limited volume in vacancies between alundum particles (α-Al2O3p)could chemically react with Al-and Mg-element in the molten AlMg10 alloy infiltrated spontaneously into the preform of alundum particles,forming solid phases and a vacuum,i.e.,a driving force for the infiltration;due to the long time contact between the molten AlMg10 alloy and alundum particles and additives,etc.,at elevated temperatures,there might be chemical reactions.
Abstract The study on the mechanism of reactive processing for the fabrication of α-Al2O3p/Al composite was performed by pressureless metal infiltration technique,optical micrography,SEM-micrography and EDS-analysis and thermodynamic consideration. This suggests the mechanism of reactive processing:the atmosphere of limited volume in vacancies between alundum particles (α-Al2O3p)could chemically react with Al-and Mg-element in the molten AlMg10 alloy infiltrated spontaneously into the preform of alundum particles,forming solid phases and a vacuum,i.e.,a driving force for the infiltration;due to the long time contact between the molten AlMg10 alloy and alundum particles and additives,etc.,at elevated temperatures,there might be chemical reactions.
1997, 14(1): 27-32.
Abstract:
Metal matrix composite materials (MMCs)were prepared using commercial pure Al as matrix,and China made Al2O3, short fiber and English Saffil Al2O3 short fiber as reinforcement. Tensile strength of the MMCs was measured. In situ observation of micro-fracture process of the MMCs and fractography of the tensile tested specimens were carried out using SEM from the experimental results, and fracture mechanisms of the MMCs were also discussed.
Metal matrix composite materials (MMCs)were prepared using commercial pure Al as matrix,and China made Al2O3, short fiber and English Saffil Al2O3 short fiber as reinforcement. Tensile strength of the MMCs was measured. In situ observation of micro-fracture process of the MMCs and fractography of the tensile tested specimens were carried out using SEM from the experimental results, and fracture mechanisms of the MMCs were also discussed.
1997, 14(1): 33-37.
Abstract:
Two metal matrix composites(MMCs),Saffil/Al-5.5Mg and Saffil/Al-5.5Zn were manufactured with the squeeze cast technique. The volume fraction of fibres was 10%,15% and 20% respectively. Optical microscopy analysis indicated that fibres appeared to be two-dimensional randomly oriented. The values of ultimate tensile strength CUTS) of matrix and MMCs were measured at room temperature and 300 C.The fracture surfaces were investigated by the scanning electron microscopy. The fracture mechanism and the reasonable formulae for the prediction of strength under various conditions were analysed and discussed.
Two metal matrix composites(MMCs),Saffil/Al-5.5Mg and Saffil/Al-5.5Zn were manufactured with the squeeze cast technique. The volume fraction of fibres was 10%,15% and 20% respectively. Optical microscopy analysis indicated that fibres appeared to be two-dimensional randomly oriented. The values of ultimate tensile strength CUTS) of matrix and MMCs were measured at room temperature and 300 C.The fracture surfaces were investigated by the scanning electron microscopy. The fracture mechanism and the reasonable formulae for the prediction of strength under various conditions were analysed and discussed.
1997, 14(1): 38-42.
Abstract:
Superplastic deformation was found in extruded SiCP-LY12 composite without any refining treatment. Maximum elongation above 150% was achieved at temperatures of 495-510 C and initial strain rate of 2×10-4s-1.Analysis of test data indicates that there is a transition of deforming mechanism near the optimum parameters,which leads to a significant increase in elongation to failure,while the value of strain rate sensitivity(m)of superplastic composites increases with elevating temperature or decreasing strain rate;however,the maximal value of m seems not corresponding to the highest value of elongation. A unique strain-hardening stage took place after the ordinary dynamic recrystallization stage and endured to failure. Microstructure observation found that dynamic recrystallization occurs in the initial stage of deformation,which hints that the unique strain hardening phenomenon might be related with recrystallized grain growth. Furthermore,interfaces between SiC particles and matrix were severely weakened during deformation and turned to be a preferential path of crack propagation。which is harmful to achieving high elongation.
Superplastic deformation was found in extruded SiCP-LY12 composite without any refining treatment. Maximum elongation above 150% was achieved at temperatures of 495-510 C and initial strain rate of 2×10-4s-1.Analysis of test data indicates that there is a transition of deforming mechanism near the optimum parameters,which leads to a significant increase in elongation to failure,while the value of strain rate sensitivity(m)of superplastic composites increases with elevating temperature or decreasing strain rate;however,the maximal value of m seems not corresponding to the highest value of elongation. A unique strain-hardening stage took place after the ordinary dynamic recrystallization stage and endured to failure. Microstructure observation found that dynamic recrystallization occurs in the initial stage of deformation,which hints that the unique strain hardening phenomenon might be related with recrystallized grain growth. Furthermore,interfaces between SiC particles and matrix were severely weakened during deformation and turned to be a preferential path of crack propagation。which is harmful to achieving high elongation.
1997, 14(1): 43-47.
Abstract:
In the (x-y) plane,thermal expansion of aluminum-matrix composites reinforced by carbon fiber with orthogonal arrangement was measured. It was found that the thermal expansion of composites in the (x-y) plane was related to heat treatment. The heat stress is analyzed in this paper. It is proved that the thermal expansion difference is caused by the internal stress of the composites.
In the (x-y) plane,thermal expansion of aluminum-matrix composites reinforced by carbon fiber with orthogonal arrangement was measured. It was found that the thermal expansion of composites in the (x-y) plane was related to heat treatment. The heat stress is analyzed in this paper. It is proved that the thermal expansion difference is caused by the internal stress of the composites.
1997, 14(1): 48-53.
Abstract:
The processing of Ceramic Matrix Composites (CMC)reinforced with 3D-braid woven fabrics via polycarbosilane (PCS) pyrolysis was investigated. Also studied were the influences of different kinds of processing on the macro and micro properties of composites. Several ways were proposed.which can improve the processing and enhance the properties of composites, The results indicate that the pyrolysis time is considerably reduced by infiltration-curing-pyrolysis of a PCS/DVB system,and the densification efficiency is significantly enhanced compared with PCS/Xylene solution infiltration. The 3D-braid Cf/SiC CMC specimens have a density of 1.65g/c3,a flexural strength of 326MPa and a fracture toughness of 13.72MPam1/2 after infiltration-curing-pyrolysis cycle. of 7 times for the PCS/DVB system,and have a density of 1.54g/c3,a flexural strength of 243MPa and a fracture toughness of 8.19MPam1/2 after infiltration-pyrolysis for the PCS/Xylene system. The fracture surfaces of the flexural specimens were also investigated by SEM including fibers pull-out,fibers fracture,etc.
The processing of Ceramic Matrix Composites (CMC)reinforced with 3D-braid woven fabrics via polycarbosilane (PCS) pyrolysis was investigated. Also studied were the influences of different kinds of processing on the macro and micro properties of composites. Several ways were proposed.which can improve the processing and enhance the properties of composites, The results indicate that the pyrolysis time is considerably reduced by infiltration-curing-pyrolysis of a PCS/DVB system,and the densification efficiency is significantly enhanced compared with PCS/Xylene solution infiltration. The 3D-braid Cf/SiC CMC specimens have a density of 1.65g/c3,a flexural strength of 326MPa and a fracture toughness of 13.72MPam1/2 after infiltration-curing-pyrolysis cycle. of 7 times for the PCS/DVB system,and have a density of 1.54g/c3,a flexural strength of 243MPa and a fracture toughness of 8.19MPam1/2 after infiltration-pyrolysis for the PCS/Xylene system. The fracture surfaces of the flexural specimens were also investigated by SEM including fibers pull-out,fibers fracture,etc.
1997, 14(1): 54-57.
Abstract:
The effect of warp and pick densities of plain fabrics to interlaminar fracture toughness (Mode Ⅰ and Mode Ⅱ)of glass-fiber plain fabric/epoxy was studied by double cantilever beam (DCB) and end notch flexure (ENF) tests. It is found that the densities of fabric will influeuce the delamination fracture toughness evidently. The problem of interlayer matrix rivetting in woven-reinforced composite materials was proposed. Moreover,the relation between rivetting and GIC and GIC values was researched.
The effect of warp and pick densities of plain fabrics to interlaminar fracture toughness (Mode Ⅰ and Mode Ⅱ)of glass-fiber plain fabric/epoxy was studied by double cantilever beam (DCB) and end notch flexure (ENF) tests. It is found that the densities of fabric will influeuce the delamination fracture toughness evidently. The problem of interlayer matrix rivetting in woven-reinforced composite materials was proposed. Moreover,the relation between rivetting and GIC and GIC values was researched.
1997, 14(1): 58-64.
Abstract:
A detailed study of damage mechanism failure process for APMOCiepoxy composite laminates in different stacking sequences was conducted by use of acoustic emission monitoring. The results showed that the relationship between AE signal parameters and damage mechanisms can be established. Obviously,AE signal parameters being recorded can reveal the dynamic damage process of the laminates. The different AE parameters relate to the different damage process and mechanisms in the laminates.
A detailed study of damage mechanism failure process for APMOCiepoxy composite laminates in different stacking sequences was conducted by use of acoustic emission monitoring. The results showed that the relationship between AE signal parameters and damage mechanisms can be established. Obviously,AE signal parameters being recorded can reveal the dynamic damage process of the laminates. The different AE parameters relate to the different damage process and mechanisms in the laminates.
1997, 14(1): 65-69.
Abstract:
The oxidation kinetics of A3-3 carbon/carbon composites was investigated at temperatures between 800~1000 C, and the experimental oxygen partial pressure was 21.3kPa.The experiment results showed that the oxidation rate of A3-3 carbon/carbon composites increases suddenly at first and then reaches a steady point. The steady oxidation rate could be expressed as r=119exp(-15613/RT)mg/cm2·h,and is not influenced by its doping elements. Otherwise,the oxidation resistance of A3-3 carbon/carbon composites is mainly determined by the carbon derived from the PF resin.
The oxidation kinetics of A3-3 carbon/carbon composites was investigated at temperatures between 800~1000 C, and the experimental oxygen partial pressure was 21.3kPa.The experiment results showed that the oxidation rate of A3-3 carbon/carbon composites increases suddenly at first and then reaches a steady point. The steady oxidation rate could be expressed as r=119exp(-15613/RT)mg/cm2·h,and is not influenced by its doping elements. Otherwise,the oxidation resistance of A3-3 carbon/carbon composites is mainly determined by the carbon derived from the PF resin.
1997, 14(1): 70-75.
Abstract:
The status and importance of materials synthesis and processing to the development of modern society and science were analyzed. A series kinds of new techniques of reaction synthesis and processing,and the status of the research of the techniques were introduced and reviewed. The states of the art of the research work done by the Chinese scientists in the relevant fields were introduced and analyzed. The problems which need to be solved and the next step work which needs to be done were suggested by the author.
The status and importance of materials synthesis and processing to the development of modern society and science were analyzed. A series kinds of new techniques of reaction synthesis and processing,and the status of the research of the techniques were introduced and reviewed. The states of the art of the research work done by the Chinese scientists in the relevant fields were introduced and analyzed. The problems which need to be solved and the next step work which needs to be done were suggested by the author.
1997, 14(1): 76-82.
Abstract:
The coefficients of thermal expansion of unidirectional fiber reinforced composites are investigated by use of homogenization method. The relationship between coefficients of thermal expansion and component properties and volume fractions is determined. A conclusion is obtamed that the influence of the property ratios of fiber and matrix on the transverse coefficients of thermal expansion is more important than on the longitudinal ones. The predictions from homog-enization method and four other analytical methods are compared with each other,and with experimental data. The assessment of validity of these different methods is made and the reliability of homogenization method is verified.
The coefficients of thermal expansion of unidirectional fiber reinforced composites are investigated by use of homogenization method. The relationship between coefficients of thermal expansion and component properties and volume fractions is determined. A conclusion is obtamed that the influence of the property ratios of fiber and matrix on the transverse coefficients of thermal expansion is more important than on the longitudinal ones. The predictions from homog-enization method and four other analytical methods are compared with each other,and with experimental data. The assessment of validity of these different methods is made and the reliability of homogenization method is verified.
1997, 14(1): 83-89.
Abstract:
The buckling behaviour of orthotropic fiber-reinforced composite laminates is analyzed by the boundary element method. In order to overcome the difficulties in finding the fundamental solution to the buckling of orthotropic laminates in boundary element method,the double Fourier series are used and a concept of equivalent load is introduced. The eigen equations of the critical loads of the laminated plates are determined. The computed examples show that the method is reliable and efficient.
The buckling behaviour of orthotropic fiber-reinforced composite laminates is analyzed by the boundary element method. In order to overcome the difficulties in finding the fundamental solution to the buckling of orthotropic laminates in boundary element method,the double Fourier series are used and a concept of equivalent load is introduced. The eigen equations of the critical loads of the laminated plates are determined. The computed examples show that the method is reliable and efficient.
1997, 14(1): 90-95.
Abstract:
A new incremental method is proposed to predict the cyclic behavior of metal-matrix composites. In each incremental step,the matrix is considered to be an anisotropic material whose stiffness tensor is chosen as the tangent moduli of the studied matrix. The Eshelby tensor for an ellipsoidal inclusion embedded in an anisotropic matrix is calculated numerically. With the aid of Mori-Tanaka mean field theory and numerical solution of the Eshelby tensor,the incremental stress and strain relation of the composite is derived. With the aid of the matrix mixed hardening law and the matrix fatigue properties,the tensile.cyclic hardening behavior and the fatigue life for a particulate reinforced are analyzed in detail;the predicted results agree quantitalively well with the ones given in the literature. In the end,the method is applied to predict the fatigue life for metal matrix composites. The comparison with experiment is also given.
A new incremental method is proposed to predict the cyclic behavior of metal-matrix composites. In each incremental step,the matrix is considered to be an anisotropic material whose stiffness tensor is chosen as the tangent moduli of the studied matrix. The Eshelby tensor for an ellipsoidal inclusion embedded in an anisotropic matrix is calculated numerically. With the aid of Mori-Tanaka mean field theory and numerical solution of the Eshelby tensor,the incremental stress and strain relation of the composite is derived. With the aid of the matrix mixed hardening law and the matrix fatigue properties,the tensile.cyclic hardening behavior and the fatigue life for a particulate reinforced are analyzed in detail;the predicted results agree quantitalively well with the ones given in the literature. In the end,the method is applied to predict the fatigue life for metal matrix composites. The comparison with experiment is also given.
1997, 14(1): 96-100.
Abstract:
Smart material and structure are the research focus of many researchers recently. This article introduces a kind of self-diagnostic smart structure which can self-diagnose the damage in real time and in a large area. The damage position and its grade can both be decided. Introduced in detail in this article are the manufacture of the smart composite test-specimen,the research of the four element arrangements and the signal processing using pattern recognition algorithm. This system can work well.
Smart material and structure are the research focus of many researchers recently. This article introduces a kind of self-diagnostic smart structure which can self-diagnose the damage in real time and in a large area. The damage position and its grade can both be decided. Introduced in detail in this article are the manufacture of the smart composite test-specimen,the research of the four element arrangements and the signal processing using pattern recognition algorithm. This system can work well.
1997, 14(1): 101-107.
Abstract:
The elastic constants of three-dimensional braided composites containing matrix microcracks were predicted by Eshelby and Mori-Tanaka theories combined with Stiffness Avcraging Method,and their variation with fiber volume fraction,microcrack density and braided parameters was analyzed. The theoretical predictions match the experimental results on reference [3] fairly well.
The elastic constants of three-dimensional braided composites containing matrix microcracks were predicted by Eshelby and Mori-Tanaka theories combined with Stiffness Avcraging Method,and their variation with fiber volume fraction,microcrack density and braided parameters was analyzed. The theoretical predictions match the experimental results on reference [3] fairly well.
1997, 14(1): 108-115.
Abstract:
Based on the three dimensional theory of piezoelectric elasticity,this paper analyzes the bending problem of simply supported thick piezoelectric composite rectangular plate with the method of state formulation. Because no assumption is introduced,the method can be used to analyzc this kind of plate with various thicknesses exactly. An intuitive expression is also obtained for the transfor matrix and the calculation is then simplified. At the end of the paper,numerical examples are given and results are discussed.
Based on the three dimensional theory of piezoelectric elasticity,this paper analyzes the bending problem of simply supported thick piezoelectric composite rectangular plate with the method of state formulation. Because no assumption is introduced,the method can be used to analyzc this kind of plate with various thicknesses exactly. An intuitive expression is also obtained for the transfor matrix and the calculation is then simplified. At the end of the paper,numerical examples are given and results are discussed.
1997, 14(1): 116-121.
Abstract:
Fiber reinforced composites are widely used in many fields. One notable application is the solid-rocket motor case. Therefore,predicting its stress and strength is extremely important. A failure analysis for predicting local damage of the structure amd making the stiffness degradation is essential to composite structures. A model with the nonlinear finite element theory was used to calculate some solid rocket motor case. Excellent agreement was found between the numerical results amd the tested ones. This method can be used to analyze the structure of filament wound composites.
Fiber reinforced composites are widely used in many fields. One notable application is the solid-rocket motor case. Therefore,predicting its stress and strength is extremely important. A failure analysis for predicting local damage of the structure amd making the stiffness degradation is essential to composite structures. A model with the nonlinear finite element theory was used to calculate some solid rocket motor case. Excellent agreement was found between the numerical results amd the tested ones. This method can be used to analyze the structure of filament wound composites.
1997, 14(1): 122-126.
Abstract:
For the first time,the moue interferometry is applied to measure the displacement field for composite joints with a pinhole. The moire pattern is used to determine the strain on the horizontal section through the pinhole centre by displacement derivative method. Based on the rectilinear normal assumption and the reduced stiffness matrix of laminates,the average stress distribution on the sections is calculated and the relative error of the experiment results is less than 6%.This rcmarch demonstrates that the moire interferometry is an efficient experimental technique for the strain and stress measurement of composite joints.
For the first time,the moue interferometry is applied to measure the displacement field for composite joints with a pinhole. The moire pattern is used to determine the strain on the horizontal section through the pinhole centre by displacement derivative method. Based on the rectilinear normal assumption and the reduced stiffness matrix of laminates,the average stress distribution on the sections is calculated and the relative error of the experiment results is less than 6%.This rcmarch demonstrates that the moire interferometry is an efficient experimental technique for the strain and stress measurement of composite joints.
1997, 14(1): 127-134.
Abstract:
Based on a method of Damage Mechanics presented by R. Talreja for study of transverse cracking in composite materials,a more reasonable method for calculation of the restricted coefficients is introduced,and used for study of transverse cracking in composite laminated plates. The variations of their elastic moduli are also predicted. Verified by the experimental results,the results of theoretical prediction are correct.
Based on a method of Damage Mechanics presented by R. Talreja for study of transverse cracking in composite materials,a more reasonable method for calculation of the restricted coefficients is introduced,and used for study of transverse cracking in composite laminated plates. The variations of their elastic moduli are also predicted. Verified by the experimental results,the results of theoretical prediction are correct.
