1985 Vol. 2, No. 3
1985, 2(3): 1-Ⅲ.
Abstract:
Toughening of an epoxy resin system for glass and carbon fiber composites is investigated.The system consists of butadiene-acrylonitrile rubber with random carboxyl groups (CTBNX),epoxy resin of diglycibyl ether of bisphenol A (DGEBA) and 2-ethyl-4-mnthy limidazol.The authors' previous studies[1,2,3] showed the following points:(1) A toughened epoxy resin can be prepared with CTBNX or GTBNX-bisphenol A to form two-phase system.The toughened epoxy resin exhibits significant improvements over the un modified ones by 2 to 10 times in impact strength,by 0.5 to 11.5 times in modulus of toughness(area under the stress-strain curve under tension) and by 1 to 4 times in fracture surface energy.(2) When the toughened epoxy resin is used as matrix for glass fiber composites,it improve longitudinal and transverse impact strength, fracture surface energy, candidate stress intensity factor KQ in unidirectional laminates and other resin-dependent mechanical properties.
Toughening of an epoxy resin system for glass and carbon fiber composites is investigated.The system consists of butadiene-acrylonitrile rubber with random carboxyl groups (CTBNX),epoxy resin of diglycibyl ether of bisphenol A (DGEBA) and 2-ethyl-4-mnthy limidazol.The authors' previous studies[1,2,3] showed the following points:(1) A toughened epoxy resin can be prepared with CTBNX or GTBNX-bisphenol A to form two-phase system.The toughened epoxy resin exhibits significant improvements over the un modified ones by 2 to 10 times in impact strength,by 0.5 to 11.5 times in modulus of toughness(area under the stress-strain curve under tension) and by 1 to 4 times in fracture surface energy.(2) When the toughened epoxy resin is used as matrix for glass fiber composites,it improve longitudinal and transverse impact strength, fracture surface energy, candidate stress intensity factor KQ in unidirectional laminates and other resin-dependent mechanical properties.
1985, 2(3): 13-Ⅳ.
Abstract:
Many design criteria mint be considered in the deaign of composite materials of strctures; amnog them the displacement, stability and vibration are considered in thin paper. The def lection, buckling stress and natural frequency of laminated circular cylindrcial shells wihtriber reinforced composite materials are discussed in detail. The shells are assumed to be simply supported at two ends,each layer of the shells is having the thickness h and an equal number of fibers of the same material in the +α: and -α: directions with the x-axis in the same type of matrix.
Many design criteria mint be considered in the deaign of composite materials of strctures; amnog them the displacement, stability and vibration are considered in thin paper. The def lection, buckling stress and natural frequency of laminated circular cylindrcial shells wihtriber reinforced composite materials are discussed in detail. The shells are assumed to be simply supported at two ends,each layer of the shells is having the thickness h and an equal number of fibers of the same material in the +α: and -α: directions with the x-axis in the same type of matrix.
1985, 2(3): 23-Ⅳ.
Abstract:
This paper deals with the in-plane bending of orthogonal wound GRP circular-shaped curv ed tubes.The features of the tubes are orthotropic,varied in thickness and without coupling effect.A series of formulas are developed for calculating the stresses and deformations of the tubes under the in-plane bending by applying the energy nethod and the ring shell theory. The their limitations are specified.Formulas for estimating the maximum stresses are given herein and demanstrated experimentally.
This paper deals with the in-plane bending of orthogonal wound GRP circular-shaped curv ed tubes.The features of the tubes are orthotropic,varied in thickness and without coupling effect.A series of formulas are developed for calculating the stresses and deformations of the tubes under the in-plane bending by applying the energy nethod and the ring shell theory. The their limitations are specified.Formulas for estimating the maximum stresses are given herein and demanstrated experimentally.
1985, 2(3): 35-Ⅴ.
Abstract:
In this paper, the effects of carhou contents and distrilmtion form on the mechanical, thermal,wear proporrties and fracture motphologies of polysnlfoue (PSF) composites have been studied.With increasing of short-CF content,the imapct strength of PSF slightly dec reases,but tensile and flexible strength increase.In the long-CF/PSF composite system these strengths increase a more prononncedlr than in short-CF/PSF composite.The interlaminar shear strength of long-CF/PSF composite is about 80% of tensile strength of PSF. CF/PSF composites have much better wear yroperties and higher thermal deformation temperature with increasinh of carbon fiber contents.Failure in CF/PSF composite appears in form of dehonding between fiber and resin.
In this paper, the effects of carhou contents and distrilmtion form on the mechanical, thermal,wear proporrties and fracture motphologies of polysnlfoue (PSF) composites have been studied.With increasing of short-CF content,the imapct strength of PSF slightly dec reases,but tensile and flexible strength increase.In the long-CF/PSF composite system these strengths increase a more prononncedlr than in short-CF/PSF composite.The interlaminar shear strength of long-CF/PSF composite is about 80% of tensile strength of PSF. CF/PSF composites have much better wear yroperties and higher thermal deformation temperature with increasinh of carbon fiber contents.Failure in CF/PSF composite appears in form of dehonding between fiber and resin.
1985, 2(3): 41-Ⅴ.
Abstract:
The density and dynamic properties of epoxy composites filled by Al2O3,CaF2 and glass microbead were investigated.It was found that a dense polymeric interface layer would be formed on the surface of solid fillers due to the interaction between particulate filler surface and epoxy matrix.The properties of interface layer are different from that of cuatrix. These composites are considered as three-element systems,consisting of filler, interface and bulk resin. From concept of "Critical concentration of the filler",the density, thickness and volume fraction of interface layer are measured.
The density and dynamic properties of epoxy composites filled by Al2O3,CaF2 and glass microbead were investigated.It was found that a dense polymeric interface layer would be formed on the surface of solid fillers due to the interaction between particulate filler surface and epoxy matrix.The properties of interface layer are different from that of cuatrix. These composites are considered as three-element systems,consisting of filler, interface and bulk resin. From concept of "Critical concentration of the filler",the density, thickness and volume fraction of interface layer are measured.
1985, 2(3): 46-Ⅵ.
Abstract:
This paper is concerned with the damage of cross-ply carben fiber reinforcod epoxy composites under static and fatigue loading.Acoustic emission, microscopie observation,infrared thermography are employed to detect the formation and prepagation of the damage and to test the fatigue behaviour. The relationships of microstructure damage with acoustic emrssion characteristic parameter and temperatuer variation are studied.The damage mechaniesm of unnotched and notched specimens are compared.
This paper is concerned with the damage of cross-ply carben fiber reinforcod epoxy composites under static and fatigue loading.Acoustic emission, microscopie observation,infrared thermography are employed to detect the formation and prepagation of the damage and to test the fatigue behaviour. The relationships of microstructure damage with acoustic emrssion characteristic parameter and temperatuer variation are studied.The damage mechaniesm of unnotched and notched specimens are compared.
1985, 2(3): 54-Ⅶ.
Abstract:
In this paper tension-tension (R=0.1) fatigue behaviour and residual static tensile strength of unidirectional graphite/epow composite were studied by using GB 3354-82 spec imens of straight-sided type with long gage length (GB-National Standard,China).The S-N curve and fatigue limit were obtained by means of test method in group and the staircase method. The number of stress cycles,at which the machine stops or the load drops due to the damage or crack occuring in the specimen,is taken as the life of the specimen at that stress level.The S-N curve ie a straight line and tends to horizon near the fatigue limit.
In this paper tension-tension (R=0.1) fatigue behaviour and residual static tensile strength of unidirectional graphite/epow composite were studied by using GB 3354-82 spec imens of straight-sided type with long gage length (GB-National Standard,China).The S-N curve and fatigue limit were obtained by means of test method in group and the staircase method. The number of stress cycles,at which the machine stops or the load drops due to the damage or crack occuring in the specimen,is taken as the life of the specimen at that stress level.The S-N curve ie a straight line and tends to horizon near the fatigue limit.
1985, 2(3): 61-Ⅶ.
Abstract:
The effect of R-Glycidoxypl trimc thozysilane (KH-560) surface treatment agent on the curing process of glass-fibre/epoxy; composite has been studied by means of torsional braid technology.When both sizing and preblending mdthods of surface treatment are used to add KH-560 into composite,the curing rate decreases and the reaction activation energy increased.
The effect of R-Glycidoxypl trimc thozysilane (KH-560) surface treatment agent on the curing process of glass-fibre/epoxy; composite has been studied by means of torsional braid technology.When both sizing and preblending mdthods of surface treatment are used to add KH-560 into composite,the curing rate decreases and the reaction activation energy increased.
1985, 2(3): 66-Ⅶ.
Abstract:
The thermal expansion properties of unidirectional fiber reinforced composites were studied in this paper. The interface adhesive coefficient C was introduced and the thermal elastic theory was used to derive the eilnatien calculating the revised linear expansion coefficient.The linear expansion coefficients of loth glass and carhon fiher reinforced composites had been measurred by thermal analysis method under different interface conditions and different fiber contents.The calculated values coincided with the measured values and the deviations were only less than 10%.
The thermal expansion properties of unidirectional fiber reinforced composites were studied in this paper. The interface adhesive coefficient C was introduced and the thermal elastic theory was used to derive the eilnatien calculating the revised linear expansion coefficient.The linear expansion coefficients of loth glass and carhon fiher reinforced composites had been measurred by thermal analysis method under different interface conditions and different fiber contents.The calculated values coincided with the measured values and the deviations were only less than 10%.
1985, 2(3): 75-Ⅷ.
Abstract:
The problem about the teclmology and thr equipmcnts for winding continous GRP pipe includes many aspects.In this paper the feasibility of automatical demoulding for "step to step" monld-axle and the raeional distribution of temperature for heatinh up the mould-axle are emphatically discussced.The prerequisite to automatical demoulding is proposed based on the mechenical an alasis.
The problem about the teclmology and thr equipmcnts for winding continous GRP pipe includes many aspects.In this paper the feasibility of automatical demoulding for "step to step" monld-axle and the raeional distribution of temperature for heatinh up the mould-axle are emphatically discussced.The prerequisite to automatical demoulding is proposed based on the mechenical an alasis.
1985, 2(3): 84-Ⅹ.
Abstract:
As we know,Perturbation Method gives an effective way to analyze nonlinear probl ems but it is still very difficuit to solve step by step the linear problems obtained from the nonlinear problems after perturbation.On the other hand,Weighted Residual Method(WRM) has been succeeded insolving linear problems,but it is also difficult to hande directly non linear algebric equations by WRM alone. In this paper, we integrate the advantage of both the perturbation and WRM for applying to solve large deflection bending problems of composite laminated thin plates.This approach consists in linearizing a nonlinear problem with perturbational method at first,then solving resulted linear one in unified form with the use of the combination of quintic B-spline function as the basis of try-function by use of Least Square and Collocation Method.
As we know,Perturbation Method gives an effective way to analyze nonlinear probl ems but it is still very difficuit to solve step by step the linear problems obtained from the nonlinear problems after perturbation.On the other hand,Weighted Residual Method(WRM) has been succeeded insolving linear problems,but it is also difficult to hande directly non linear algebric equations by WRM alone. In this paper, we integrate the advantage of both the perturbation and WRM for applying to solve large deflection bending problems of composite laminated thin plates.This approach consists in linearizing a nonlinear problem with perturbational method at first,then solving resulted linear one in unified form with the use of the combination of quintic B-spline function as the basis of try-function by use of Least Square and Collocation Method.
1985, 2(3): 88-Ⅸ.
Abstract:
This paper improves on the early work's modal[1].A generalized plane strain computer programm is formulated with 8 nodes isoparameter element.The initial yield surfaces of unidirectiornally reinforced composites are obtained with the change in fiber volume fractions and the concentration factor is given under transverse loading. The results of the paper are useful without doubt to composite material designs and micro-failure mechanism analysis.
This paper improves on the early work's modal[1].A generalized plane strain computer programm is formulated with 8 nodes isoparameter element.The initial yield surfaces of unidirectiornally reinforced composites are obtained with the change in fiber volume fractions and the concentration factor is given under transverse loading. The results of the paper are useful without doubt to composite material designs and micro-failure mechanism analysis.
