1994 Vol. 11, No. 4
1994, 11(4): 1-8.
Abstract:
Two thermotropic copolyeters BP-LCP and BPM-LCP have been synthesised.A series of in-situ somposites which composed of polysulfone and copolyesters with different molecular weight have been prepared.The effects of chain structure,molecular weight and content of.LCP on formation of microfiber have been discussed,and the action of shear and stretch on microfiber been investigated.It is proposed that the lower of the compatibility, the better of the microfiber.And the results obtained show that the remakable microfiber is formed when the content of high molecular weight BP-LCP is more.
Two thermotropic copolyeters BP-LCP and BPM-LCP have been synthesised.A series of in-situ somposites which composed of polysulfone and copolyesters with different molecular weight have been prepared.The effects of chain structure,molecular weight and content of.LCP on formation of microfiber have been discussed,and the action of shear and stretch on microfiber been investigated.It is proposed that the lower of the compatibility, the better of the microfiber.And the results obtained show that the remakable microfiber is formed when the content of high molecular weight BP-LCP is more.
1994, 11(4): 9-13.
Abstract:
Wood/plastic Conposite material is a new kind of synthetic materials with wood flour and waste plactic as its main ingredients.In this paper,the ingredients and processes of this material are stuffed.At the same time,the relationships between them and the properties of the synthetic materials are also discussed.
Wood/plastic Conposite material is a new kind of synthetic materials with wood flour and waste plactic as its main ingredients.In this paper,the ingredients and processes of this material are stuffed.At the same time,the relationships between them and the properties of the synthetic materials are also discussed.
1994, 11(4): 14-19.
Abstract:
Recently the subject of the application of XPS on surface analysis got fast development.This paper is to introduce the application of XPS to composite materials.For example,surface elements,surface groups and their contects in fiber before and after treatment,surface graft degree,curing degree of resin and acidbasicity of surface and so on are determined.
Recently the subject of the application of XPS on surface analysis got fast development.This paper is to introduce the application of XPS to composite materials.For example,surface elements,surface groups and their contects in fiber before and after treatment,surface graft degree,curing degree of resin and acidbasicity of surface and so on are determined.
1994, 11(4): 20-25.
Abstract:
The interfacial bonding between aramid fiber and epoxy resins cured by triethylene tetramine is usually very weak,which limits the aramid fiber composite application.In this work,silane coupling agents were used for the surface treatment-of the Kevlar-49 fibers,the interfacial strength was studied by means of single fiber pull-out tests.It turned out that the shear strength (τ0)of interface,the energy of interface fracture (G1)and pull-out friction (Ff) were affected by the structure of silanes.2# was recognized to be the best one among the six studied silanes.After treatment with 2# the G,increased from 45J/m2 to 72J/m2 and the friction force Ff/L,from 15cN/mm to 21cN/mm.
The interfacial bonding between aramid fiber and epoxy resins cured by triethylene tetramine is usually very weak,which limits the aramid fiber composite application.In this work,silane coupling agents were used for the surface treatment-of the Kevlar-49 fibers,the interfacial strength was studied by means of single fiber pull-out tests.It turned out that the shear strength (τ0)of interface,the energy of interface fracture (G1)and pull-out friction (Ff) were affected by the structure of silanes.2# was recognized to be the best one among the six studied silanes.After treatment with 2# the G,increased from 45J/m2 to 72J/m2 and the friction force Ff/L,from 15cN/mm to 21cN/mm.
1994, 11(4): 26-32.
Abstract:
The fabricating processing of carbon fiber reinforced aluminium laminate (CFALL) has been investigated.With the technique,the laminate with excellent mechanical properties,high temperature resistance and fatigue property has been obtained.The effect of the volume fraction and direction of carbon fiber,and temperature on the mechanical properties of CFALL was also researched.The further detail of fatigue and the effect of prestraining on the fatigue of CFALL was also carried out.The results show that CFALL is characterized by low density,high strength,high temperature resistance and excellent fatigue property.The tensile and flexure strength of CFALL are higher than the corresponding values of ARALL and GLALL,and the fatigue property of CFALL is comparable with that of ARALL.
The fabricating processing of carbon fiber reinforced aluminium laminate (CFALL) has been investigated.With the technique,the laminate with excellent mechanical properties,high temperature resistance and fatigue property has been obtained.The effect of the volume fraction and direction of carbon fiber,and temperature on the mechanical properties of CFALL was also researched.The further detail of fatigue and the effect of prestraining on the fatigue of CFALL was also carried out.The results show that CFALL is characterized by low density,high strength,high temperature resistance and excellent fatigue property.The tensile and flexure strength of CFALL are higher than the corresponding values of ARALL and GLALL,and the fatigue property of CFALL is comparable with that of ARALL.
1994, 11(4): 33-38.
Abstract:
Friction and wear properties of randomly oriented carbon fibre/ZA-12 matrix composites fabricated by squeeze casting were studied.The effect of carbon fibre content (Vf) and load on the coefficient of friction and the wear loss of the composites was investigated.The wear surface was observed by scanning electron microscope.The effect on the friction and wear properties of the composites was discussed.
Friction and wear properties of randomly oriented carbon fibre/ZA-12 matrix composites fabricated by squeeze casting were studied.The effect of carbon fibre content (Vf) and load on the coefficient of friction and the wear loss of the composites was investigated.The wear surface was observed by scanning electron microscope.The effect on the friction and wear properties of the composites was discussed.
1994, 11(4): 39-43.
Abstract:
Damping behavior at low frequency was studied on aluminium silicon-matrix graphite particles composites with the method of internal friction technique.The dependence of damping on graphite content,frequency,temperature,strain amplitude,and the variation of elastic modulus were investigated.The damping characteristics of as-cast and as-extruded composites were compared.The preliminary inquiry was made on the damping mechanisms of the composite materials.
Damping behavior at low frequency was studied on aluminium silicon-matrix graphite particles composites with the method of internal friction technique.The dependence of damping on graphite content,frequency,temperature,strain amplitude,and the variation of elastic modulus were investigated.The damping characteristics of as-cast and as-extruded composites were compared.The preliminary inquiry was made on the damping mechanisms of the composite materials.
1994, 11(4): 44-48.
Abstract:
1994, 11(4): 49-54.
Abstract:
The damage of multiple cracking in the interphase may occur before the fiber breaking,which causes the strength of the fiber to descrease seriously.In this article,with four-phase concentric circular cylinder mode (that is,fiber,interphase,matrix and composite material),and assuming that the interface between the fiber and the interphase can't transfer shear stress after debonding,the stressconcentration of the fiber and the interphase caused by the multiple cracking were calculated by using of shear-lag method,then with Weibull distribution function,the change of the cumulative probability of fiber failure was discussed.Finally,the influence of the interface shear strengthτ0 on the fiber strength was studied.It is fund that there is the optimum interface shear strength τ0.
The damage of multiple cracking in the interphase may occur before the fiber breaking,which causes the strength of the fiber to descrease seriously.In this article,with four-phase concentric circular cylinder mode (that is,fiber,interphase,matrix and composite material),and assuming that the interface between the fiber and the interphase can't transfer shear stress after debonding,the stressconcentration of the fiber and the interphase caused by the multiple cracking were calculated by using of shear-lag method,then with Weibull distribution function,the change of the cumulative probability of fiber failure was discussed.Finally,the influence of the interface shear strengthτ0 on the fiber strength was studied.It is fund that there is the optimum interface shear strength τ0.
1994, 11(4): 55-60.
Abstract:
Numerical calculation of the elastic engineering constants of unidirectional fibre composites based on an effective medium theory (EMT)[4] is here employed to find the Young's modulus of 2-dimensional as well as 3-dimensional randomly oriented fibre composites by a method of geometrical average over orientations due to Christensen & Waals[3].The results compare faverably with similar calculations based on theories of Halpin-Tsai[8] and Christensen[7],and show good conformity with experimental data.Thus it is shown that EMT is applicable to the calculation of elastic properties of randomly oriented fibre composites.
Numerical calculation of the elastic engineering constants of unidirectional fibre composites based on an effective medium theory (EMT)[4] is here employed to find the Young's modulus of 2-dimensional as well as 3-dimensional randomly oriented fibre composites by a method of geometrical average over orientations due to Christensen & Waals[3].The results compare faverably with similar calculations based on theories of Halpin-Tsai[8] and Christensen[7],and show good conformity with experimental data.Thus it is shown that EMT is applicable to the calculation of elastic properties of randomly oriented fibre composites.
1994, 11(4): 61-68.
Abstract:
A simple higher-order shear deformation theory for laminated composite plates is developed.Its displacement field accounts for the continue of displacement and shear stresses between layers,and ensure that τxx、τyx on the plate surfaces are equal to the loads.The theory contains the same unkows as in the first-order shear deformation theory,but its solutions are much more exact.The theory includs reasonably the affect of loads paralleling the plate surfaces,and the precision for analysing these problems is improved considerably.
A simple higher-order shear deformation theory for laminated composite plates is developed.Its displacement field accounts for the continue of displacement and shear stresses between layers,and ensure that τxx、τyx on the plate surfaces are equal to the loads.The theory contains the same unkows as in the first-order shear deformation theory,but its solutions are much more exact.The theory includs reasonably the affect of loads paralleling the plate surfaces,and the precision for analysing these problems is improved considerably.
1994, 11(4): 69-75.
Abstract:
The static compressive characteristics of glass micro-ballon/epoxy composites of three different densities were experimentally determined and their fractographs were analysed.In-site observations of the micro-structure during the fracture process were carried out.Experiments were done on Instron testing machine and SEM with its loading stage.The elastic constants and ultimate compressive strengths of the materials were determined.Based on the results of the micro-observations,the fracture patterns,deformation features, bondine conditions and the wav of fracture of the materials were discussed.
The static compressive characteristics of glass micro-ballon/epoxy composites of three different densities were experimentally determined and their fractographs were analysed.In-site observations of the micro-structure during the fracture process were carried out.Experiments were done on Instron testing machine and SEM with its loading stage.The elastic constants and ultimate compressive strengths of the materials were determined.Based on the results of the micro-observations,the fracture patterns,deformation features, bondine conditions and the wav of fracture of the materials were discussed.
1994, 11(4): 76-80.
Abstract:
A Preliminary model for the analysis of thermo-mechanical behavior of interfacial coating on fibers in unidirectional composites was developed on the solution of thermo-elastic mechanics.The low modulus coating can effectively reduce the interfacial stress caused by different thermal expansion coefficient between fibers and matrix,no matter how high or low the expansion coefficients of coatings are in CF/Al and SiC/Ti systems,however,high modulus coating can decrease the interfacial compressive stress,only when the thermal expomsion of coating is low.
A Preliminary model for the analysis of thermo-mechanical behavior of interfacial coating on fibers in unidirectional composites was developed on the solution of thermo-elastic mechanics.The low modulus coating can effectively reduce the interfacial stress caused by different thermal expansion coefficient between fibers and matrix,no matter how high or low the expansion coefficients of coatings are in CF/Al and SiC/Ti systems,however,high modulus coating can decrease the interfacial compressive stress,only when the thermal expomsion of coating is low.
1994, 11(4): 81-88.
Abstract:
A finite element computer program is developed for composite golf shaft designer to make the ideal choice of shaft structure in relation to players.A club with composite shaft can be designed for a special golfer with the program.The motion of golf club during swing is divided into two parts:rigid boby motion and vibration.In rigid motion,the club is considered as a bar with a concentrated mass.A two nodal element is used to calculate the dynamic responses of the club during vibration.Impact force caused by impact are calculated based on static indentation test and the impact force is used to predict the motion of the Golf ball after impact.The computed strain results are compared with the test results and both of them agree well.
A finite element computer program is developed for composite golf shaft designer to make the ideal choice of shaft structure in relation to players.A club with composite shaft can be designed for a special golfer with the program.The motion of golf club during swing is divided into two parts:rigid boby motion and vibration.In rigid motion,the club is considered as a bar with a concentrated mass.A two nodal element is used to calculate the dynamic responses of the club during vibration.Impact force caused by impact are calculated based on static indentation test and the impact force is used to predict the motion of the Golf ball after impact.The computed strain results are compared with the test results and both of them agree well.
1994, 11(4): 89-94.
Abstract:
The platuea stresses of honeycombs and their corresponding deformation mechanisms are analysed under in-plane uniaxial loading condition.It shows that a new deformation mechanism,plastic buckling,may occur when the bending resistability of cell is strong enough.The influences of geometry and material property of cell on the platurs stresses and corresponding deformation mechanisms are discussed for elastic,perfectly plastic materials.
The platuea stresses of honeycombs and their corresponding deformation mechanisms are analysed under in-plane uniaxial loading condition.It shows that a new deformation mechanism,plastic buckling,may occur when the bending resistability of cell is strong enough.The influences of geometry and material property of cell on the platurs stresses and corresponding deformation mechanisms are discussed for elastic,perfectly plastic materials.
1994, 11(4): 95-103.
Abstract:
The effect of water environment on the growth of delamihation fatigue cracks was investigated with unidirectional laminates' made from ICI APC-2 thermoplastic prepregs (AS4/PEEK).Tests were carried out under mode I opening loading by using double cantilever beam specimens.the testing environment was water at 23℃ and 50℃.Moisture conditioned specimens were also tested in water at 23℃,The water envirnoment did not induce large detrimental effects.The crack growth rate was expressed as two power functions of the equivalent stress intensity range.The exponent of the power functions in the low growth rate region was smaller than that in the high growth rate region.lowering the frequency of stress cycling yielded accelerated crack growth in water,suggesting the time-dependent mechanism of crack growth.The difference of the enviromental effects between CF/PEEK and CF/epoxy laminates was discussed on the basis of the fractographic observation and mechanism consideration.
The effect of water environment on the growth of delamihation fatigue cracks was investigated with unidirectional laminates' made from ICI APC-2 thermoplastic prepregs (AS4/PEEK).Tests were carried out under mode I opening loading by using double cantilever beam specimens.the testing environment was water at 23℃ and 50℃.Moisture conditioned specimens were also tested in water at 23℃,The water envirnoment did not induce large detrimental effects.The crack growth rate was expressed as two power functions of the equivalent stress intensity range.The exponent of the power functions in the low growth rate region was smaller than that in the high growth rate region.lowering the frequency of stress cycling yielded accelerated crack growth in water,suggesting the time-dependent mechanism of crack growth.The difference of the enviromental effects between CF/PEEK and CF/epoxy laminates was discussed on the basis of the fractographic observation and mechanism consideration.
1994, 11(4): 104-109.
Abstract:
Impact tests of compressed T300/QY8911 laminates are carried out in this paper. Ultrasonic scanning,metallographic technique and deplying method are used to give a careful observation and description of impact damage,and relatively comprehensive microscopic damage features are obtained.Studies show that delamination is the major damage form and occurs in almost all interfaces.The shape of every delamination is irregular,and the axis of it coincides with the fiber orientation of the lamina beneath the interface.The delamination area is related to the angle between fiber directions of two adjacent laminate and stacking sequence of them.The pre-compression has a greater effect on the distribution of inner delaminations,and the most serious delamination is located at the interface near the midplane at the back of the laminate.
Impact tests of compressed T300/QY8911 laminates are carried out in this paper. Ultrasonic scanning,metallographic technique and deplying method are used to give a careful observation and description of impact damage,and relatively comprehensive microscopic damage features are obtained.Studies show that delamination is the major damage form and occurs in almost all interfaces.The shape of every delamination is irregular,and the axis of it coincides with the fiber orientation of the lamina beneath the interface.The delamination area is related to the angle between fiber directions of two adjacent laminate and stacking sequence of them.The pre-compression has a greater effect on the distribution of inner delaminations,and the most serious delamination is located at the interface near the midplane at the back of the laminate.
1994, 11(4): 110-116.
Abstract:
The tensile impact loading-unloading test of unidirectional glass fiber reinforced epoxy are carried out on a self-designed tensile impact setup in the first time.Combined with the results of transient temperature rising and energy analysis under tensileimpact,a perfect composed bundle model is proposed and the one-dimensional constitutive equation under tensile impact is derived.Comprehensive tensileimpact tests in the strain rate range(300-2000 l/s)for that composite are carried on.The specific constitutive equation simulated from the statistical analysis and rate-dependence analysis of the testing results shows effective and possesses obvious physical meaning.
The tensile impact loading-unloading test of unidirectional glass fiber reinforced epoxy are carried out on a self-designed tensile impact setup in the first time.Combined with the results of transient temperature rising and energy analysis under tensileimpact,a perfect composed bundle model is proposed and the one-dimensional constitutive equation under tensile impact is derived.Comprehensive tensileimpact tests in the strain rate range(300-2000 l/s)for that composite are carried on.The specific constitutive equation simulated from the statistical analysis and rate-dependence analysis of the testing results shows effective and possesses obvious physical meaning.
