1989 Vol. 6, No. 2
1989, 6(2): 1-8,14.
Abstract:
In this paper,the express of the stress and displacement field of a dissimilar orthotropic laminate with an interfacialedg crack(delamination),under antiplane shear loading,satisfying all of the basic equations,boundary conditions along the crack surfaces and conditions of continuity along the ligament of the interface are obtained by the menthod of complex variable.Furthermore,the coefficient of the singular term(stress intensity factor) is determined by the variational method for multi-regions.The computation results show a satistactory convergency of the stress intensity factors and the calculation is very time-saving.
In this paper,the express of the stress and displacement field of a dissimilar orthotropic laminate with an interfacialedg crack(delamination),under antiplane shear loading,satisfying all of the basic equations,boundary conditions along the crack surfaces and conditions of continuity along the ligament of the interface are obtained by the menthod of complex variable.Furthermore,the coefficient of the singular term(stress intensity factor) is determined by the variational method for multi-regions.The computation results show a satistactory convergency of the stress intensity factors and the calculation is very time-saving.
1989, 6(2): 9-Ⅱ.
Abstract:
To establish the stress-strain relationship and strength criterion of 3D carbon-carbon rriaterial,it is imperstive to acliievcari experimental technique to realize the combined state of stresses.The conventional,thinwalled tulle specimen cannot.be used since the fiber bundles of 3D,carbon-carbon material are woven in three otrhogonal directions and to fabricate a tube will cut the fiber bundles and cause a teduction in specimen strength and change the stress-strain relationship.In view of sepcific mechauical properties of 3D carbon-carbon material,the cruciform specimen was employed.In order to ensure the failure of the material will occur in the central gage area,the thickness of central gage area was milled thinner without injuring the remaining fiber bundles in that reg ion.On the cruciform specimens,the vertical force was exerted from a testing machine while the horizontal force was brought to bear by a specially designed loading setup hung freely on a frame with pulleys with negligible friction.To achieve Tension-shear testings,a modified Iocipescu setup was comployed.The shear stear of 3D carbon-carbon material is so large as to amount to scores of 103 με.To measure such a large strain,a specially designed measuring device was fabricated.The experimental result show that the stress-strain relationships under tension-tension,tension-compression and compression compression arc linear.The nonlinearity stems only from shear,In the case of combined stress state with tension stress in one direction and compression in the another,to determine whether the tension or compression modulus should be used,this paper suggests that the fiber bundle stresses instead of principal stresses will doffiinate,The symmetry of the elastic coefficient matrix is attained by assuming the existence of strain potential.Strength data are fitted with quadratic function separately in each quadrant of the stress plane,Both the constitutive equations and strength criteria thus established agree with the experimental results fairly well.
To establish the stress-strain relationship and strength criterion of 3D carbon-carbon rriaterial,it is imperstive to acliievcari experimental technique to realize the combined state of stresses.The conventional,thinwalled tulle specimen cannot.be used since the fiber bundles of 3D,carbon-carbon material are woven in three otrhogonal directions and to fabricate a tube will cut the fiber bundles and cause a teduction in specimen strength and change the stress-strain relationship.In view of sepcific mechauical properties of 3D carbon-carbon material,the cruciform specimen was employed.In order to ensure the failure of the material will occur in the central gage area,the thickness of central gage area was milled thinner without injuring the remaining fiber bundles in that reg ion.On the cruciform specimens,the vertical force was exerted from a testing machine while the horizontal force was brought to bear by a specially designed loading setup hung freely on a frame with pulleys with negligible friction.To achieve Tension-shear testings,a modified Iocipescu setup was comployed.The shear stear of 3D carbon-carbon material is so large as to amount to scores of 103 με.To measure such a large strain,a specially designed measuring device was fabricated.The experimental result show that the stress-strain relationships under tension-tension,tension-compression and compression compression arc linear.The nonlinearity stems only from shear,In the case of combined stress state with tension stress in one direction and compression in the another,to determine whether the tension or compression modulus should be used,this paper suggests that the fiber bundle stresses instead of principal stresses will doffiinate,The symmetry of the elastic coefficient matrix is attained by assuming the existence of strain potential.Strength data are fitted with quadratic function separately in each quadrant of the stress plane,Both the constitutive equations and strength criteria thus established agree with the experimental results fairly well.
1989, 6(2): 15-Ⅲ.
Abstract:
The doubly curved orthotropic laminated shell is considered in this paper,The shell may be composed of an arbitary number of bounded layers,each of which may posses different thickness and elastic properties.In this theory the displacements between layers are considered as fundamental unknown functions.The transverse shear deformation extensional strain in earch lamina is included.Equations of equlibrium for laminae are first derived.The continuity of displacement and stress has been prescribed at the interfaces between laminae before the final governing equations are derived.
The doubly curved orthotropic laminated shell is considered in this paper,The shell may be composed of an arbitary number of bounded layers,each of which may posses different thickness and elastic properties.In this theory the displacements between layers are considered as fundamental unknown functions.The transverse shear deformation extensional strain in earch lamina is included.Equations of equlibrium for laminae are first derived.The continuity of displacement and stress has been prescribed at the interfaces between laminae before the final governing equations are derived.
1989, 6(2): 24-Ⅲ.
Abstract:
By taking unsymmetrically angleply laminated plates of anisotropic composites as an example to make an analysis of tha complete solution analysis process (including calculating examples) of non-linear flexural forced vibration of plates under the harmonic force,the writers obtain amplitude-frequency relationship of anisotropic unsymmetrically angle-ply laminated plates under the load of different-magnitude,and the effect of the change in plying layers of laminated plats upon the amplitude-frepuency relationship of non-linear flexural forced vibration.The solution analysis result thus obtained is reliable and the conclusion drawn from the result is representative.What has been done so far is undoubtedly a meaningful attempt in the matter of non-linear dynamics of anisotropic laminated plates and will be a great help in the further research of some other note-linear dynamics of anisotropic laminated plates.
By taking unsymmetrically angleply laminated plates of anisotropic composites as an example to make an analysis of tha complete solution analysis process (including calculating examples) of non-linear flexural forced vibration of plates under the harmonic force,the writers obtain amplitude-frequency relationship of anisotropic unsymmetrically angle-ply laminated plates under the load of different-magnitude,and the effect of the change in plying layers of laminated plats upon the amplitude-frepuency relationship of non-linear flexural forced vibration.The solution analysis result thus obtained is reliable and the conclusion drawn from the result is representative.What has been done so far is undoubtedly a meaningful attempt in the matter of non-linear dynamics of anisotropic laminated plates and will be a great help in the further research of some other note-linear dynamics of anisotropic laminated plates.
1989, 6(2): 31-Ⅳ.
Abstract:
In this paper,it is shown that,by introducing a function of displacement,the governing equations in ref,[1] for the classical laminate theory of orthotropic la urinated cylindrical shell can be reduced to one equation in terms of displacement function,On the basis of such a differential equation and by extending W.Nowacki's method,an analytical solution to the problem of buckling of a laminated composite cylin drical shell with longitudinal ribs is given.The reliability of the function of displacement is checked by calculating some examples in which all the parameters refered to the ribs are neglected.T he calculated results of the critical loads are exactly equal to those in ref,[1],which shows that the derived displacement function is correct.The calculated results of the examples also show that the influence of ribs obviously exists,generally,the values of the critical load for laminated composite cylindrical shells without ribs are lower than the corresponding ones for cylindrical shells with reinforced longitudinal ribs.
In this paper,it is shown that,by introducing a function of displacement,the governing equations in ref,[1] for the classical laminate theory of orthotropic la urinated cylindrical shell can be reduced to one equation in terms of displacement function,On the basis of such a differential equation and by extending W.Nowacki's method,an analytical solution to the problem of buckling of a laminated composite cylin drical shell with longitudinal ribs is given.The reliability of the function of displacement is checked by calculating some examples in which all the parameters refered to the ribs are neglected.T he calculated results of the critical loads are exactly equal to those in ref,[1],which shows that the derived displacement function is correct.The calculated results of the examples also show that the influence of ribs obviously exists,generally,the values of the critical load for laminated composite cylindrical shells without ribs are lower than the corresponding ones for cylindrical shells with reinforced longitudinal ribs.
1989, 6(2): 39-Ⅴ.
Abstract:
A theoretical analysis is presented for the postbuckling behaviour of simply supported orthotropic rectangular Plates subjected to combinedo in-plane biaxial compression and edge shear,By perturbation technique and selecting the perturbation parrrieter relating to the maximum deflection,the nonlinear coupled partial differential epuations are reduced to a system of uncoupled linear partial differential equations and then salved by using the double Fourier series method.Numerical results are obtained for glass-epoxy composite plates,The effect of aspect ratio and loading parameter on the postbuckling behaviour is illustrated graphically and discussed.The numerical results show a good convergence of the present solution and they are in good agreement with the available data.
A theoretical analysis is presented for the postbuckling behaviour of simply supported orthotropic rectangular Plates subjected to combinedo in-plane biaxial compression and edge shear,By perturbation technique and selecting the perturbation parrrieter relating to the maximum deflection,the nonlinear coupled partial differential epuations are reduced to a system of uncoupled linear partial differential equations and then salved by using the double Fourier series method.Numerical results are obtained for glass-epoxy composite plates,The effect of aspect ratio and loading parameter on the postbuckling behaviour is illustrated graphically and discussed.The numerical results show a good convergence of the present solution and they are in good agreement with the available data.
1989, 6(2): 48-Ⅵ.
Abstract:
The laminate with different construction,i.e,with laminae laying up with different orientations,will have different failure sequence and different final damage state from which the strength can be predicted,The failure sequence of laminae in a laminate can be determined by a stress analysis integrated with an apropriate strength criterion.The stress analysis will be extremely complicated due to the randomness and rich variety of damage modes.
The laminate with different construction,i.e,with laminae laying up with different orientations,will have different failure sequence and different final damage state from which the strength can be predicted,The failure sequence of laminae in a laminate can be determined by a stress analysis integrated with an apropriate strength criterion.The stress analysis will be extremely complicated due to the randomness and rich variety of damage modes.
1989, 6(2): 55-Ⅵ.
Abstract:
Based on the laminated beam theory established in ref.[1],the dynamic governing equations of laminated beams on elastic foundations obtained and simplified to give the dynamic governing equations which do not include transverse shear deformations.The corresponding exact solutions of free vibrating of laminated beams on elastic foundations are obtained by using these two different governing equations,and the effect of transverse shear deformations is also discussed on the characteristic frequency of laminated beams.
Based on the laminated beam theory established in ref.[1],the dynamic governing equations of laminated beams on elastic foundations obtained and simplified to give the dynamic governing equations which do not include transverse shear deformations.The corresponding exact solutions of free vibrating of laminated beams on elastic foundations are obtained by using these two different governing equations,and the effect of transverse shear deformations is also discussed on the characteristic frequency of laminated beams.
1989, 6(2): 61-Ⅶ.
Abstract:
The thermoplastic nylon-1010 is rainforced with short general purpose (GP) pitch-based carbon fibers,KH-550 treated high-strength glass fibers and their hybrid fibers.Results show that both stiffness and strength may be increased and the extent of this improvement is dependent on the nature of the fibers used and the fiber volume fraction.The mechanical properties of the hybrid carbon/glass fibre reinforced nylon-1010 composite are better than those of the pure pitch-based carbon fiber tomposite,The fracture feature of theses composites and the "hybrid effect" have also been studied.
The thermoplastic nylon-1010 is rainforced with short general purpose (GP) pitch-based carbon fibers,KH-550 treated high-strength glass fibers and their hybrid fibers.Results show that both stiffness and strength may be increased and the extent of this improvement is dependent on the nature of the fibers used and the fiber volume fraction.The mechanical properties of the hybrid carbon/glass fibre reinforced nylon-1010 composite are better than those of the pure pitch-based carbon fiber tomposite,The fracture feature of theses composites and the "hybrid effect" have also been studied.
1989, 6(2): 68-Ⅶ.
Abstract:
Birefringent behaviors of some currently used fiber-reinforced sites and transparent filament-resin photoelastic rriaterials were investi gated by using a self-made Laser Optical Microscopic Analyzer(LOMA).The birefringent characteristics were estimated based on a I-O curve recorded,where I is the light intensity transmitted normally through polarizers and a specimen,and O is the pass plane of the polarizer.
Birefringent behaviors of some currently used fiber-reinforced sites and transparent filament-resin photoelastic rriaterials were investi gated by using a self-made Laser Optical Microscopic Analyzer(LOMA).The birefringent characteristics were estimated based on a I-O curve recorded,where I is the light intensity transmitted normally through polarizers and a specimen,and O is the pass plane of the polarizer.
1989, 6(2): 74-Ⅷ.
Abstract:
The optimum design of composite laminated structures subjected to multiple constraints,such as stresses,displacements and frepuency,is described in this paper,Variables are ply thicknesses and angles of or thotropy,A new method,quasianalytic sequence quadratic program method(SQP),is applied.With this method,a computer program SOD is compiled.Computational results for several typical examples show that the SQP method performs satisfactorily,and a considerable weight reduction can be achieved in tho optimum design of composite laminated structures.
The optimum design of composite laminated structures subjected to multiple constraints,such as stresses,displacements and frepuency,is described in this paper,Variables are ply thicknesses and angles of or thotropy,A new method,quasianalytic sequence quadratic program method(SQP),is applied.With this method,a computer program SOD is compiled.Computational results for several typical examples show that the SQP method performs satisfactorily,and a considerable weight reduction can be achieved in tho optimum design of composite laminated structures.
1989, 6(2): 84-89.
Abstract:
A minimum weight design on a composite aircraft wing structure subjected to displacements and size constraints conducted in this paper,The ply-thicknesses of composite skin are stimulated by polynomials.The Finite element method is ussd in the structural analysis.A feasible direction approach is applied to the optimum proc0dures.The coefficients of polynomials and the thicknesses or sectional are,as of finite elements are taken as design variables,By grouping the variables,the scale of the problem is deduced,Examples of a composite material box sector and a composite material wing strure show satisfactory results.
A minimum weight design on a composite aircraft wing structure subjected to displacements and size constraints conducted in this paper,The ply-thicknesses of composite skin are stimulated by polynomials.The Finite element method is ussd in the structural analysis.A feasible direction approach is applied to the optimum proc0dures.The coefficients of polynomials and the thicknesses or sectional are,as of finite elements are taken as design variables,By grouping the variables,the scale of the problem is deduced,Examples of a composite material box sector and a composite material wing strure show satisfactory results.
