1991 Vol. 8, No. 2
1991, 8(2): 1-8.
Abstract:
Based on energy equivalence Principle,a finite element stochastic enorgy method is presented to predict the mechanical propertics of short fiber composite materials.The method is a combined method of the finite element method with Monte carlo stochsstic sampling method.Some theoretical predicting results of mechanical properties of Carbon/AG3,Carbon/AG321 and Steel/Urethane as numerical examples are given in the paper.The agrcement of the numerical predicting results with expcrimental results shows that the modal and methcd provided in tho papwr is reasonable and effective.
Based on energy equivalence Principle,a finite element stochastic enorgy method is presented to predict the mechanical propertics of short fiber composite materials.The method is a combined method of the finite element method with Monte carlo stochsstic sampling method.Some theoretical predicting results of mechanical properties of Carbon/AG3,Carbon/AG321 and Steel/Urethane as numerical examples are given in the paper.The agrcement of the numerical predicting results with expcrimental results shows that the modal and methcd provided in tho papwr is reasonable and effective.
1991, 8(2): 9-17.
Abstract:
A damaged elasto-brittle material constitutive relation in incremental form which consideres anisotropy of both material and damage is presented in this paper.The formula calculating the tensors(including the damage modulus,the offcctive elastic modulus and the kinetic elastic modulus as well) are also derived.And based on this clastc-brittle damage theory and method,the structural finies element procedure taking local damage into account and its application to simulato damage-failure process of composite plate has been given, Finally the calculating results of the damage process of a glass-fiber woven/epoxy composite plate with a central holl under tensile loading have been shown in the form of equi-damage lines and their change.
A damaged elasto-brittle material constitutive relation in incremental form which consideres anisotropy of both material and damage is presented in this paper.The formula calculating the tensors(including the damage modulus,the offcctive elastic modulus and the kinetic elastic modulus as well) are also derived.And based on this clastc-brittle damage theory and method,the structural finies element procedure taking local damage into account and its application to simulato damage-failure process of composite plate has been given, Finally the calculating results of the damage process of a glass-fiber woven/epoxy composite plate with a central holl under tensile loading have been shown in the form of equi-damage lines and their change.
1991, 8(2): 19-24.
Abstract:
An analysis is made on the studying approaches of +θ/-θ interlaminar fracture toughness of composit-laminates.Under certain mechanical conditions the experimental techniques may becused to determine the "pure mechanical part" Gm of Gc.Combined with the "pure thermal part"GT evaluated numcrically,the value of Gc can be obtainced. A sufficiant condition is raised for DCB specimens.Under that condition,experiments and finite clement analysis are conducted for T300/648 and T300/QY8911 systems,which give the +θ/-θ interlaminer Gc for the range of θ=θ=0°～30°.The,The efffcts of large deformation are discussed and a new correction factor is propesed.A further discussicn is rnade on θ effectc and fractography.
An analysis is made on the studying approaches of +θ/-θ interlaminar fracture toughness of composit-laminates.Under certain mechanical conditions the experimental techniques may becused to determine the "pure mechanical part" Gm of Gc.Combined with the "pure thermal part"GT evaluated numcrically,the value of Gc can be obtainced. A sufficiant condition is raised for DCB specimens.Under that condition,experiments and finite clement analysis are conducted for T300/648 and T300/QY8911 systems,which give the +θ/-θ interlaminer Gc for the range of θ=θ=0°～30°.The,The efffcts of large deformation are discussed and a new correction factor is propesed.A further discussicn is rnade on θ effectc and fractography.
1991, 8(2): 25-32.
Abstract:
The buckling of a circular dclaminate near the surface of a thick laminato is soudied in this paper.Thv thickness of the sublaminate is assumed to be small comparcd with the total laminate thickness.The transverse deflection including a bending-torsion and shear-extension coupling terms is suppcsed and the Rayleighgh-Ritz method is used for the analysis. Effects of the base laminate Poisson's ratio,radius of delaminate and layup on buckling strains are discussed.The results show that(1) the buckling strainse and ara indcpendent on the Poisson's ratio;(2)the buckling strains. increase when the the base laminate Poisson's ratio increases;(3)if there is tension buckling strain is determined by the Poisson's ratio only.
The buckling of a circular dclaminate near the surface of a thick laminato is soudied in this paper.Thv thickness of the sublaminate is assumed to be small comparcd with the total laminate thickness.The transverse deflection including a bending-torsion and shear-extension coupling terms is suppcsed and the Rayleighgh-Ritz method is used for the analysis. Effects of the base laminate Poisson's ratio,radius of delaminate and layup on buckling strains are discussed.The results show that(1) the buckling strainse and ara indcpendent on the Poisson's ratio;(2)the buckling strains. increase when the the base laminate Poisson's ratio increases;(3)if there is tension buckling strain is determined by the Poisson's ratio only.
1991, 8(2): 33-40.
Abstract:
This paper presents two calculation methods for determining transverse shear stiffness coefficients,weight function method and strain energy method.The first method is similar to that proposed in Ref.〔1〕,with the exception of abandoning the assumption of parabolic distribution of transverse shear stress through thickness of the lamicate.Becaus the real distribution of shear stress is not exactly parabelie,especially for unsymmetrical laminates,the formula in Ref.〔1〕often yields inaccuracy. First of all,the formulas of transverse shear stress were derived.The least square method wa,s used to obtain the approximate weight functions for both symmetrical and unsytrimetrical laminates.Then.the shear stiffness coefficients were calculated by using the two methods. The results show that for the unsyrrirrtetrical laminat:the weight functiara method is better than the formula of Ref.〔1〕.As foe the comperison between the two methods of this paper,strain energy rnethod might be supcrior to the other one.
This paper presents two calculation methods for determining transverse shear stiffness coefficients,weight function method and strain energy method.The first method is similar to that proposed in Ref.〔1〕,with the exception of abandoning the assumption of parabolic distribution of transverse shear stress through thickness of the lamicate.Becaus the real distribution of shear stress is not exactly parabelie,especially for unsymmetrical laminates,the formula in Ref.〔1〕often yields inaccuracy. First of all,the formulas of transverse shear stress were derived.The least square method wa,s used to obtain the approximate weight functions for both symmetrical and unsytrimetrical laminates.Then.the shear stiffness coefficients were calculated by using the two methods. The results show that for the unsyrrirrtetrical laminat:the weight functiara method is better than the formula of Ref.〔1〕.As foe the comperison between the two methods of this paper,strain energy rnethod might be supcrior to the other one.
1991, 8(2): 41-46.
Abstract:
The present note proposes a new nonlocal model of interface with semi-inffinite nterfacial crack,which relates the displacement jump to the traction(sce the formula(6)).Specially,for the case where the power of the stress singuiarity is equal to(1/2),we drive a simple relationship(see the formula(10)). in which this a typical nonlocal length,and K1 the interface constant. A similar ratationship can also btabtained between [ut] and σt.
The present note proposes a new nonlocal model of interface with semi-inffinite nterfacial crack,which relates the displacement jump to the traction(sce the formula(6)).Specially,for the case where the power of the stress singuiarity is equal to(1/2),we drive a simple relationship(see the formula(10)). in which this a typical nonlocal length,and K1 the interface constant. A similar ratationship can also btabtained between [ut] and σt.
1991, 8(2): 47-50.
Abstract:
By deriving the relation between the accuracy of strength test and the failure position of composite materials,as well as the probabilities of specimen breaking at different regions this paper studies the effect of stress concentration test on strength accuracy are test results of composites materials.The methods to improve also discussed.
By deriving the relation between the accuracy of strength test and the failure position of composite materials,as well as the probabilities of specimen breaking at different regions this paper studies the effect of stress concentration test on strength accuracy are test results of composites materials.The methods to improve also discussed.
1991, 8(2): 51-56.
Abstract:
The effects of fiber aspect ratio on the dynamic mechanical properties for both the glass/epoxy and carbon/epoxy composites have been investigated. The results show that the mechanical internal friction of materials reduce and the modulus enhances with fiber aepoct ratio.After a certain aspect ratio both the internal frictionwand modulus begin to levol off and to approach the values of continuous f fiber composite.Therefore,the f fiber utilization cfficicncy is fully played.The internal friction of carbon fiber composite is higher than that of glass one.The higher the test temperature and the lower the matrix modulus,the fiber efficiency will be lower.Hence,the aspect ratio for the same of fiber eff iciency will be higher.The phenomenon mentioned above cold be acccunted by that the stressces in the ffibers and at the fiber/resin interface along the length of the fibers would change with aspect ratio under the external loading or the thermal shrinkage stresses are applied.
The effects of fiber aspect ratio on the dynamic mechanical properties for both the glass/epoxy and carbon/epoxy composites have been investigated. The results show that the mechanical internal friction of materials reduce and the modulus enhances with fiber aepoct ratio.After a certain aspect ratio both the internal frictionwand modulus begin to levol off and to approach the values of continuous f fiber composite.Therefore,the f fiber utilization cfficicncy is fully played.The internal friction of carbon fiber composite is higher than that of glass one.The higher the test temperature and the lower the matrix modulus,the fiber efficiency will be lower.Hence,the aspect ratio for the same of fiber eff iciency will be higher.The phenomenon mentioned above cold be acccunted by that the stressces in the ffibers and at the fiber/resin interface along the length of the fibers would change with aspect ratio under the external loading or the thermal shrinkage stresses are applied.
1991, 8(2): 57-62.
Abstract:
In the present paper the creep curves of glass fiber reinforced polypropy-lene are measured by the creep test in tensile conditions.Based on the proposed Theological models the constitutive equations of creep are constructed and the rheological paraments are obtained. The effects of temperature and the quantity of glass fiber upon the Theological behavior are further discussed.
In the present paper the creep curves of glass fiber reinforced polypropy-lene are measured by the creep test in tensile conditions.Based on the proposed Theological models the constitutive equations of creep are constructed and the rheological paraments are obtained. The effects of temperature and the quantity of glass fiber upon the Theological behavior are further discussed.
1991, 8(2): 63-70.
Abstract:
The processing and performance of continuous carbon fiber reinforced polyethersulphone(PES)were evaluated.An improved method for fabricating prepregs of continuous fiber/thermoplastic composites was suggested and an optimum forming process was supplied.The obtained T300/PES composite showed low void rate and excellent mechanical performance,the apparent interlaminar shear strength being as high as 82.7MPa.Lastly,the fracture modes and morphologies of T300/PES composite were analysed.
The processing and performance of continuous carbon fiber reinforced polyethersulphone(PES)were evaluated.An improved method for fabricating prepregs of continuous fiber/thermoplastic composites was suggested and an optimum forming process was supplied.The obtained T300/PES composite showed low void rate and excellent mechanical performance,the apparent interlaminar shear strength being as high as 82.7MPa.Lastly,the fracture modes and morphologies of T300/PES composite were analysed.
1991, 8(2): 71-76.
Abstract:
The paper is about measuriug curing ruction of SY-25 adhcsiv DSC-7 of PFRKIN-ELMER Company.Kinetic parameters of curing reaction activation energy, reaction order and pre-exponcntial factor can be obtained based on the kinetic equation which is constructed.in accordance with the measuring principle of DSC-7.Using the kinetic parameters,the relationship among degree of curing,curing temporeture and curing time is predicted.This work may be used to proviole a throretical data for making curing technology parameters of SY-25 adhesive.
The paper is about measuriug curing ruction of SY-25 adhcsiv DSC-7 of PFRKIN-ELMER Company.Kinetic parameters of curing reaction activation energy, reaction order and pre-exponcntial factor can be obtained based on the kinetic equation which is constructed.in accordance with the measuring principle of DSC-7.Using the kinetic parameters,the relationship among degree of curing,curing temporeture and curing time is predicted.This work may be used to proviole a throretical data for making curing technology parameters of SY-25 adhesive.
1991, 8(2): 77-83.
Abstract:
The processing of silicon carbide reinforced with carbon fibre by nmans of polycarbosilane(PC) chemical transformation was studied in this work.The mismatch of thermal expansion coefficient between carbon fibre and silicon carbide matrix was alleviated by the addition of a small amount of zirconia to the matrix.The composite material possesses much improved toughness due to the fibre incorporation.The results of mechanical and thermal experiments show that the composite has good comprehensive properties.
The processing of silicon carbide reinforced with carbon fibre by nmans of polycarbosilane(PC) chemical transformation was studied in this work.The mismatch of thermal expansion coefficient between carbon fibre and silicon carbide matrix was alleviated by the addition of a small amount of zirconia to the matrix.The composite material possesses much improved toughness due to the fibre incorporation.The results of mechanical and thermal experiments show that the composite has good comprehensive properties.
1991, 8(2): 85-90.
Abstract:
The dry cliding wear behavior of SiCw whisker reinforces aluminium(SiCw/Al)compositer was ctudied.The wear mechanism map was presented in thispaper.The microm chanism of wear damage was further analyzed according to the wear surface morphology and wear mechanism map.Scals-like wear morphology was also discussed with a modal proposed in this paper.
The dry cliding wear behavior of SiCw whisker reinforces aluminium(SiCw/Al)compositer was ctudied.The wear mechanism map was presented in thispaper.The microm chanism of wear damage was further analyzed according to the wear surface morphology and wear mechanism map.Scals-like wear morphology was also discussed with a modal proposed in this paper.
1991, 8(2): 91-96.
Abstract:
Impact fracture bshavior of SiC whisker reinforced 6061AL metal matrix composites has been studied by combining SEAM fractographic analysis and instrumented charpy testing.As compared with that of isotropic SiCw/6061Al composite in which SiCw were randomly oriented,the hot-extruded composite has higher impact toughness.It is shown that hot-extrusion improves the properties of SiCw/6061 Al composites.Delamination fracture phenomenon was observcd. The impact fracture models of SiCw/6061Al corriposites were discussed in detail. The impact fracture behavior of the composite after extrusion is different from that of the as-fabricated composite.The reasons why the impact toughness was improved by extrusion of SiCw/6061Al. were analysed.
Impact fracture bshavior of SiC whisker reinforced 6061AL metal matrix composites has been studied by combining SEAM fractographic analysis and instrumented charpy testing.As compared with that of isotropic SiCw/6061Al composite in which SiCw were randomly oriented,the hot-extruded composite has higher impact toughness.It is shown that hot-extrusion improves the properties of SiCw/6061 Al composites.Delamination fracture phenomenon was observcd. The impact fracture models of SiCw/6061Al corriposites were discussed in detail. The impact fracture behavior of the composite after extrusion is different from that of the as-fabricated composite.The reasons why the impact toughness was improved by extrusion of SiCw/6061Al. were analysed.
