1996 Vol. 13, No. 4
1996, 13(4): 1-7.
Abstract:
Abstract The structures, electrical and thermal conductivity and their temperature dependences of the composites, which were prepared with polyethylene or polystyrene filled by polypyrrole particles, were investgated. It was found that the fabrication procedure inllu-ences the homogeneity of composite, the conductive threshold and characterization of the composites. The variation of thermal conductivity can be described by a series model. The relationship between the fabrication procedure, volume fraction of polymer particles strutures and conductive characterization of the composites was also discussed.
Abstract The structures, electrical and thermal conductivity and their temperature dependences of the composites, which were prepared with polyethylene or polystyrene filled by polypyrrole particles, were investgated. It was found that the fabrication procedure inllu-ences the homogeneity of composite, the conductive threshold and characterization of the composites. The variation of thermal conductivity can be described by a series model. The relationship between the fabrication procedure, volume fraction of polymer particles strutures and conductive characterization of the composites was also discussed.
1996, 13(4): 8-11.
Abstract:
Abstract The resistivity of cement specimens under different pressures was studied. The specimens are mixed with carbon fibres. The results show that when pressure gets larger and larger, the resistivity of specimens changes.This process can be divided into three parts:reversible sensing period, balance period and sharp increasing period. These three periods respectively show the closure opening of original cracks, the embryo of new flaws and def,cts extending to failure. The conducting mechanism is also analyzed. The characteristic of carbon fibre cement can be used in the non-destructive detection of concrete dams etc.
Abstract The resistivity of cement specimens under different pressures was studied. The specimens are mixed with carbon fibres. The results show that when pressure gets larger and larger, the resistivity of specimens changes.This process can be divided into three parts:reversible sensing period, balance period and sharp increasing period. These three periods respectively show the closure opening of original cracks, the embryo of new flaws and def,cts extending to failure. The conducting mechanism is also analyzed. The characteristic of carbon fibre cement can be used in the non-destructive detection of concrete dams etc.
1996, 13(4): 12-15.
Abstract:
Behavior for of moisture sorption of aromatic polyamide fibers(AF) was studied, the diffusion coefficient was calculated and, in the meantime, the effect of moisture sorption of composite on ILSS was studied. It is found that the moisture sorption of AF was increased after plasma treatment, and the ILSS of composite was not lowered but raised. After the fibers were soaked in water, the drop percent in ILSS of composite was decreased; especially for moisture, the drop percent in ILSS of composite was evidently decreased. This is because the chemical bond of interface was introduced after plasma treatment, and its interfac, cohesive strength and water-resisting property were increased.
Behavior for of moisture sorption of aromatic polyamide fibers(AF) was studied, the diffusion coefficient was calculated and, in the meantime, the effect of moisture sorption of composite on ILSS was studied. It is found that the moisture sorption of AF was increased after plasma treatment, and the ILSS of composite was not lowered but raised. After the fibers were soaked in water, the drop percent in ILSS of composite was decreased; especially for moisture, the drop percent in ILSS of composite was evidently decreased. This is because the chemical bond of interface was introduced after plasma treatment, and its interfac, cohesive strength and water-resisting property were increased.
1996, 13(4): 16-19.
Abstract:
Abstract The effects of liquid crystalline polymers’ structure, thermal history and compatibilizers on the transition temperatures of polysulfone with thermotropic liquid crystalline polymers’ in-situ composites were studied. The compatibility of polysulfone and liquid crystalline polymers obeyed the similar structure rule, and it could be improved by adding block copolymers.High heating rate could get a big peak in DSC curve, and it is easy to obtain Tg value by second heating. The thermal mechanical properties of these blends were also studied.
Abstract The effects of liquid crystalline polymers’ structure, thermal history and compatibilizers on the transition temperatures of polysulfone with thermotropic liquid crystalline polymers’ in-situ composites were studied. The compatibility of polysulfone and liquid crystalline polymers obeyed the similar structure rule, and it could be improved by adding block copolymers.High heating rate could get a big peak in DSC curve, and it is easy to obtain Tg value by second heating. The thermal mechanical properties of these blends were also studied.
1996, 13(4): 20-24.
Abstract:
The experiment of using modifier B to improve the dissolvability of the prepolymer of bismaleimide/diamine is reported. The prepolymer can be dissolved in acetone easily and the solution has enough long harmonious stage at room temperature. It makes convenient for preparing prepreg.Meanwhile, the properties of resins have been studied by DSC and TG analysis method and the composite's performance is characterized by interlaminar shear strength(ILSS) at room temperature, 150℃ and 200℃.
The experiment of using modifier B to improve the dissolvability of the prepolymer of bismaleimide/diamine is reported. The prepolymer can be dissolved in acetone easily and the solution has enough long harmonious stage at room temperature. It makes convenient for preparing prepreg.Meanwhile, the properties of resins have been studied by DSC and TG analysis method and the composite's performance is characterized by interlaminar shear strength(ILSS) at room temperature, 150℃ and 200℃.
1996, 13(4): 25-29.
Abstract:
The superplasticity of aluminum matrix fabricated by spray atomization and co-dleposition was investigated. Before superplastic deformation, the pretreatment of hot compress and hot forward extrusion was utilized. Fine gains and uniformly distributed SiCP in SiCP/LY12 composite are observed. The results of superplastically uniaxial tension show that the SiCP/LY12 composite has good superplasticity and the limit elongation and m-value are greatly affected by the temperature and strain rate. Moreover, the limit elongation is 345% in this compositewith 500℃ of temperature and 1.0×10-3s-1 of initial strain rate.
The superplasticity of aluminum matrix fabricated by spray atomization and co-dleposition was investigated. Before superplastic deformation, the pretreatment of hot compress and hot forward extrusion was utilized. Fine gains and uniformly distributed SiCP in SiCP/LY12 composite are observed. The results of superplastically uniaxial tension show that the SiCP/LY12 composite has good superplasticity and the limit elongation and m-value are greatly affected by the temperature and strain rate. Moreover, the limit elongation is 345% in this compositewith 500℃ of temperature and 1.0×10-3s-1 of initial strain rate.
1996, 13(4): 30-33.
Abstract:
The effects of stress, temperature and heat-treatment on the steady state creep rate of 22vol% short Mullite fiber reinforced LY12 composites were studied. A creep mehanism of cxunposites was advanced. The creep behavior of composites was controlled by the climb of dislocation at low stress state and by the interface conditions at high stress state. The interfac, of cxunposites was analysed by TEM.
The effects of stress, temperature and heat-treatment on the steady state creep rate of 22vol% short Mullite fiber reinforced LY12 composites were studied. A creep mehanism of cxunposites was advanced. The creep behavior of composites was controlled by the climb of dislocation at low stress state and by the interface conditions at high stress state. The interfac, of cxunposites was analysed by TEM.
1996, 13(4): 34-38.
Abstract:
Based on the empirical electron theory of solids and molecules, the bonding complex models of the martensitic cell are set up, and an analysis of VES for alloying element(V) on the Ms of NiTi shape memory alloysis made. Some preliminary attempts at revealing the relatio nship between alloy composition-structure -property and NiTi alloy martensitic VES are presented.
Based on the empirical electron theory of solids and molecules, the bonding complex models of the martensitic cell are set up, and an analysis of VES for alloying element(V) on the Ms of NiTi shape memory alloysis made. Some preliminary attempts at revealing the relatio nship between alloy composition-structure -property and NiTi alloy martensitic VES are presented.
1996, 13(4): 39-56.
Abstract:
1996, 13(4): 47-52.
Abstract:
A description is given of the effect of hight emperaturet reatment on tribological properties of carbon/carbon(C/C) composites prepared by chemical vapour deposition. The curve diagram of brake moment-brake time of different temperaturet reated samples was anayzed. The results indicated that the average dynamic frictional coefficient(FC) of C/C composites was decreased in drycondition, but dam pcondition average dynamic FC and drycondition averagestatic FC were increased as temperature was increased. After C/C composites were treated under 2500℃, they had smooth brake process and small wear, and their average dynamic FC was slowly decreased in dampcondition. The average dynamic FC of four kinds of samples treated under different temperatures was reduced in dry and dampcondition as brake pressure and energy were raised.
A description is given of the effect of hight emperaturet reatment on tribological properties of carbon/carbon(C/C) composites prepared by chemical vapour deposition. The curve diagram of brake moment-brake time of different temperaturet reated samples was anayzed. The results indicated that the average dynamic frictional coefficient(FC) of C/C composites was decreased in drycondition, but dam pcondition average dynamic FC and drycondition averagestatic FC were increased as temperature was increased. After C/C composites were treated under 2500℃, they had smooth brake process and small wear, and their average dynamic FC was slowly decreased in dampcondition. The average dynamic FC of four kinds of samples treated under different temperatures was reduced in dry and dampcondition as brake pressure and energy were raised.
1996, 13(4): 53-57.
Abstract:
Electro rheological fluids were selected as the active vibration control of smart composite structures. The experimental investigations were focused on evaluating the elasto-dynamic response charact eristics of beams featuring electror heological fluids when the beams were subject ed to forced vibration. Meantime, the active vibration control of smart composite beams is studied. The results of these considerations clearly demonstrate the ability to significantly change the vibrational characteristics of beams fabricated in smart composites by changing the electric field imposed on the fluid domain. A conclusion is made that the shear modulus of ER fluids can be controlled by the application of an electric field to the ER material.
Electro rheological fluids were selected as the active vibration control of smart composite structures. The experimental investigations were focused on evaluating the elasto-dynamic response charact eristics of beams featuring electror heological fluids when the beams were subject ed to forced vibration. Meantime, the active vibration control of smart composite beams is studied. The results of these considerations clearly demonstrate the ability to significantly change the vibrational characteristics of beams fabricated in smart composites by changing the electric field imposed on the fluid domain. A conclusion is made that the shear modulus of ER fluids can be controlled by the application of an electric field to the ER material.
1996, 13(4): 58-63.
Abstract:
Using boundary element method, a study is given on the inter facial fracture toughness of a bimaterial fourpoint bending specimen with either perfector imperfect interface. The complex stress intensity factor and the strain energy density in the tip of interface cracks are calculated for these two kinds of specimens respectively. It is found that within most distance spanned by the innerloading points the above two quantities at tain essentially constant values. This stable behavior will facilitate the test of interfacial fracture toughness.
Using boundary element method, a study is given on the inter facial fracture toughness of a bimaterial fourpoint bending specimen with either perfector imperfect interface. The complex stress intensity factor and the strain energy density in the tip of interface cracks are calculated for these two kinds of specimens respectively. It is found that within most distance spanned by the innerloading points the above two quantities at tain essentially constant values. This stable behavior will facilitate the test of interfacial fracture toughness.
1996, 13(4): 64-69.
Abstract:
A new type of structure of vehicleplate spring-glass/epoxy cliping layer plate spring was designed and manufactured. Finite elementmet hod is used to study stress and place moving field inside the structure and electric measure method is utilized to verify the result of calculation. At the end, the advantage of this structure design is explained.
A new type of structure of vehicleplate spring-glass/epoxy cliping layer plate spring was designed and manufactured. Finite elementmet hod is used to study stress and place moving field inside the structure and electric measure method is utilized to verify the result of calculation. At the end, the advantage of this structure design is explained.
1996, 13(4): 70-74.
Abstract:
Fracture to ughness of PP/AT Composites was studied by means of the method created by williams, et al. which was developed on the basis of LEFM. By utitizing a simple and economical method in which varying measure scales are required, the fractal dimension of fracture surfaces can be determined conveniently. After relating fractal dimension to fracture toughness, it is found that the fractal dimension increases with increasing fracture toughness. This means that fracture to ughness can be inferred by the fractal dimension of fracture surface.
Fracture to ughness of PP/AT Composites was studied by means of the method created by williams, et al. which was developed on the basis of LEFM. By utitizing a simple and economical method in which varying measure scales are required, the fractal dimension of fracture surfaces can be determined conveniently. After relating fractal dimension to fracture toughness, it is found that the fractal dimension increases with increasing fracture toughness. This means that fracture to ughness can be inferred by the fractal dimension of fracture surface.
1996, 13(4): 75-81.
Abstract:
A new test method is presented to determine the stress and strain within the syn-thetic material parts using super high frequency electromagnetic wave of the polarization to transmit it. The relationship between the stress, strain and dielectric constant, the structure and working principle of the test instrument, and the practical examples are given.
A new test method is presented to determine the stress and strain within the syn-thetic material parts using super high frequency electromagnetic wave of the polarization to transmit it. The relationship between the stress, strain and dielectric constant, the structure and working principle of the test instrument, and the practical examples are given.
1996, 13(4): 82-88.
Abstract:
Anidea of stiffness partition is proposed to develop the constitutive relations foracracked composite laminate with anisotropic constraint layers. The governing equation of the coupled stiffness problem is derived after partition. As an example, the stiffness degradation for cracked(-θm/90n/θm)s laminates is studied.
Anidea of stiffness partition is proposed to develop the constitutive relations foracracked composite laminate with anisotropic constraint layers. The governing equation of the coupled stiffness problem is derived after partition. As an example, the stiffness degradation for cracked(-θm/90n/θm)s laminates is studied.
1996, 13(4): 89-94.
Abstract:
The compression and tension mechanical behaviors of short fibre reinforced composite material——PPS(Polyphenylene sulfide) overa wide range of strain rates covering six orders of magnitude are described. The fracture appearance and the cross-section of tested specimens were observed. The results show that the strength and Young smodulus of the short fiber reinforced thermoplastic PPS increase with increasing strain rates and reveal that the fracture of short fibre-reinf orced PPS exhibits brittle behavior. The results indicate that the strain rate effect is remarkable.
The compression and tension mechanical behaviors of short fibre reinforced composite material——PPS(Polyphenylene sulfide) overa wide range of strain rates covering six orders of magnitude are described. The fracture appearance and the cross-section of tested specimens were observed. The results show that the strength and Young smodulus of the short fiber reinforced thermoplastic PPS increase with increasing strain rates and reveal that the fracture of short fibre-reinf orced PPS exhibits brittle behavior. The results indicate that the strain rate effect is remarkable.
1996, 13(4): 95-101.
Abstract:
A general solution for piezothermoelastic materials is obtained by applying the extended version of Stroh's formulation when all eigenvalues are distinct. When some piezoelectric eigenvalues are equal, the general solution for this degenerate casehas also been given and discussed. Attention is also paid to the case where the heat eigenvalue pair becomes equal to one ormore pairs of the piezoelectric eigenvalues and the particular solution for this degenerate piezot hermoel astic problem is also given. Finally, it is shown that one can make the form of the arbitrary function fα(zα) for the degenerate piezotherm oelastic solution the same as that for the undegenerate case except for some parameters included in the form ulation.
A general solution for piezothermoelastic materials is obtained by applying the extended version of Stroh's formulation when all eigenvalues are distinct. When some piezoelectric eigenvalues are equal, the general solution for this degenerate casehas also been given and discussed. Attention is also paid to the case where the heat eigenvalue pair becomes equal to one ormore pairs of the piezoelectric eigenvalues and the particular solution for this degenerate piezot hermoel astic problem is also given. Finally, it is shown that one can make the form of the arbitrary function fα(zα) for the degenerate piezotherm oelastic solution the same as that for the undegenerate case except for some parameters included in the form ulation.
1996, 13(4): 102-111.
Abstract:
Abstract Computational methods for simulating and predicting progressive fracture in composite structures are the current important research subject in composite community and these researches are of significant practical use. The fundamental principles of the progres-sive damage models and the state-of-the artreview of these methods are presented. Furthermore, two types of interface elements, spring interface elements and six-noded interface elemenu, which are developed by the present author and can be used to predict delamination failure of composites, are introduced in detail. Many examples are provided which show good agreement between theoretical predictions and experiments. These examples indicate that it is very possible to simulate the progressive fracture of cxunposite structures with a computer.
Abstract Computational methods for simulating and predicting progressive fracture in composite structures are the current important research subject in composite community and these researches are of significant practical use. The fundamental principles of the progres-sive damage models and the state-of-the artreview of these methods are presented. Furthermore, two types of interface elements, spring interface elements and six-noded interface elemenu, which are developed by the present author and can be used to predict delamination failure of composites, are introduced in detail. Many examples are provided which show good agreement between theoretical predictions and experiments. These examples indicate that it is very possible to simulate the progressive fracture of cxunposite structures with a computer.
1996, 13(4): 102-111.
Abstract:
Computational methods for simulating and predicting progressive fracture in composite structures are the current important research subject in composite community and these researches are of significant practical use. The fundamental principles of the progressive damage models and the state-of-the-art review of these methods are presented. Further-more, two types of interface elements, spring interface elements and six-noded int erface elements, which are developed by the present author and can be used to predict delamination failure of composites, are int roduced in detail. Many examples are provided which show good agreement between theoretical predictions and experiments. These examples indicate that it is very possible to simulate the progressive fracture of composite structures with a computer.
Computational methods for simulating and predicting progressive fracture in composite structures are the current important research subject in composite community and these researches are of significant practical use. The fundamental principles of the progressive damage models and the state-of-the-art review of these methods are presented. Further-more, two types of interface elements, spring interface elements and six-noded int erface elements, which are developed by the present author and can be used to predict delamination failure of composites, are int roduced in detail. Many examples are provided which show good agreement between theoretical predictions and experiments. These examples indicate that it is very possible to simulate the progressive fracture of composite structures with a computer.
1996, 13(4): 112-113.
Abstract:
Using the Simple High-order Shear Deformation Laminate Theory and large deformation theory, the geometricnonlinear analysis of rubber rectangular composite laminate plate is presented. Compared with the linear theory, the results, including stress and strain distributions, are more reasonable.
Using the Simple High-order Shear Deformation Laminate Theory and large deformation theory, the geometricnonlinear analysis of rubber rectangular composite laminate plate is presented. Compared with the linear theory, the results, including stress and strain distributions, are more reasonable.
1996, 13(4): 117-122.
Abstract:
Based on the secant modulus method and Weibull statistic law, a microm echanical method is advanced to model the matrix plastic deformation and the particulate cracking for metal matrix composites during straining. The influences of the particul at emean size and its scatter on the composite macroscopic behavior are analyzed in details. It is found that the particulate mean size plays a key role in the composite damage properties. The theor etical results fora SiCP/Al composite agree well with the experimental ones in the literature.
Based on the secant modulus method and Weibull statistic law, a microm echanical method is advanced to model the matrix plastic deformation and the particulate cracking for metal matrix composites during straining. The influences of the particul at emean size and its scatter on the composite macroscopic behavior are analyzed in details. It is found that the particulate mean size plays a key role in the composite damage properties. The theor etical results fora SiCP/Al composite agree well with the experimental ones in the literature.
