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Acoustic emission monitoring of stress corrosion cracks in aligned GRP
apparatus is described, and its performance discussed. The morphology of the resulting ribbon was studied by optical and electron microscopy. This showed that the presence of a wire may reduce the cross-section of the ribbon. The reduction in cooling rate caused by the inclusion of the wire may result in the formation of embriltling crystallites.
Damage in composites-modeling of imperfect bonding Aboudi, J. Composites Science and Technology Vol 28 No 2 (1987) pp 103-128 A mathematical model which incorporates damage due to the imperfect bonding between reinforcing fibres and matrix is presented. The model may bc used to predict overall moduli anti coefficients of thermal expansion.
GENERAL
Delamination growth in angle-ply laminated composites Kim, K.D. anti Hong, C.S.Journal ol'Composite Materials Vo120 (Sepwmber 1986) pp 423-438 The stability of dclamination crack growth in angle-ply laminates subjected to mechanical and thermal loading were analysed using the rule-of-mixtures and the strain-energy release rate concept in linear fracture mechanics. A quasi three-dimensional finite element method was used. The effect of delamination on the tensile strength lbr small fibre angles was also evaluated. The authors conclude that mode 3 is the dominant fracture mode of free edge delamination. Delamination was found to be influenced by fibre orientation, ply thickness, thermal residual stresses (which play a significant role) and loading conditions (tensile/compressive). It was found that thicker laminates delaminate at lower strain levels. The tensile strength results from the present analysis were closer to experimental results than those predicted using the failure criterion for small fibre angles.
Accelerated environmental conditioning of corn posites Lee, W.l., Ciriscioli. P.R. and Springer, G.S. S4MPE Quarterly Vol 17 No 4 (July 1986) pp 27-31 A procedure which has been developed to reduce the time required to perform environmental tests is described. Equations are given which provide the environmental conditions leading to the fastest moisture uptake in the organic matrix and charts are presented from which the conditions for accelerated tests can be obtained. On the analysis and design of the end notched flexure (ENF) specimen for Mode I! testing Carlsson, L.A.. Gillespie Jr, J.W. and Pipes, R.B, Journal q/'('ompo~ite Materials Vo120 (November 1986) pp 594-604 An extension of the beam theory solution to invcstigate the influence of interlaminar shear deformation and friction between the crack surfaces on the strain-energy release rate is presented. The optimum design for an endnotched flexure specimen, to obtain a linear response, is presented. It was [ound that for reasonable coefficients of friction, the error in G u induced by neglecting friction was only 2-4%. "['he influence of the interlaminar shear dclormation may be minimized by using beams with small thickness-to-crack length ratios. Analysis of progressive failure in composites Ochoa, O.O. and Engblom. J.J. ('omposite,s Sciem'e and I~'chnolo,W Vol 28 No 2 (1987) pp ,W-102 An incrcmcnlal failure accumulation technique is presented for angle-ply, cross-ply and uniaxial composite laminates. Piecewise smooth failure criteria that distinguish between lhe failure modes arc implemented in a finite clement analysis. The analytical capability of this progressive failure method which distinguishes between failure modes and traces failure progression to ultimate laminate failure is dcmunstrated for uniaxial tension and fourpoint bending problems. Boundary element study of a loaded hole in an orthotropic plate Mahajcrin, E. and Sikarskie, D.L. Journal Of Composite MuteriaL~ Vol 20 (July 1986) pp 375-389 A boundary element method (BEM) for the analysis of mechanically fastened composites is presented. The traditional BEM method was modified to allow for the determination of boundary stress and displacements. An analytical scheme was developed lbr the evaluation of boundary integrals in elements containing singularities and combined with a special integration quadrature formula for the remaining elements. Accurate results were obtained for the stress concentration factors lbr different hole sizes and various boundary conditions. The method was compared directly with the finite element method.
264
Effect of fibre and matrix maximum strain on the energy absorption of composite materials Farley, (i.L. Journal o[ Composite Materials Vol 20 (July 1986) pp 322-334 The el'feet of fibre and matrix maximum strain at failure on the energy ubsorption of a variety of commercial graphite reinIorccd composites was investigated. Static crushing tests were perlbrmed on chamfered tube specimens and the specific sustained crushing stress was used to compare the energy-absorbing capability of thc different tubes. The crushing characteristics demonstrated that for maximum energy absorption from a particular fibre, the matrix material in the composite must have a greatcr strain at failure than the fibre. The effect of load distribution on the strength of pin loaded holes in laminated eomposites Chang, F.K. Journal o[' Composite MateriaLv Vol 20 (July 1986) pp 401-409 The effect of an assumed cosine load distribution in the inside boundary of the hole, on the calculated strength and predicted failure mode of pin-loaded holes, was compared with the calculated results from a knowledge of the actual displacements on the inside surface of a hole. The strengths and failurc modes calculated by both mcthods were found to agree closely when using the Yamada-Sun failure criterion with the Chang-Scott-Springer characteristic curve. Fibre inclination model of three-dimensional textile structural composites Yang, J.-M., Ma, C.-L., Chou, T.-W. Journal q[' Composites Material.s; Vol 20 (September 1986) pp 472-484 The effective in-plane elastic moduli of threedimensional textile composites were analysed using modified classical laminate plate theory and a fibre inclination model. In this model, the unit cell treats the yarns as being composed of straight segments of an inclincd unicfircctional
laminate oriented in different directions. The results show reasonably good agreement with experimental data.
FTIR characterization of advanced materials Young, P.R. and Chang, A.C. SAMPE Quarterly Vol 17 No 4 (July 1986) pp 32-38 A survey of Fourier transform infrared spectroscopy sampling techniques as applied to resins, fibres, prepregs and composites is presented. Scveral promising specialized FTIR techniques are discussed. The optimal design of symmetric laminated beams considering damping Liao, D.X., Sung, C.K and Thompson, B.S. Journal (?.[Composite Materials Vo120 (Sepwmber 1986) pp 485-501 An experimentally validated analytical model for laminate damping was incorporated into an optimization algorithm to establish a viable design tool to synthesize laminated beams for optimal damping anti stiffness. The thickness of each ply. its location relative to the plane of beam symmetry and the orientation of fibres in each ply wcrc considered. IHustrativc examples tbr several test problems arc presented including the constraint condition of invariable flexural rigidity. Predicting the orientation of short fibres in thin compression mouldings Jackson, W.C., Advani, S.G. and Tucker. C.L Journal of ('omposite Materials Vo120 (November 1986) pp 539-557 A method is presented for predicting the orientation of short, rigid fibres in thin compression moulded parts. The method extends Folgar and Tuckers orientation model to show how a mould filling simulation can be combined with the orientation mode[ to predict the fibre orientation in moulded purls in the presence of non-homogcncous flow fields. A generalized Hele-Shaw modcl was used to predict flow and deformation during mould filling. The results of the calculations compare favourably with experiments on sheet moulding compound and a model suspension of nylon fibres in siliconc oil.
Simple design for reliable high performance laminates Spencer, A.M. Composiws Science and Techno/ogy Vol 28 No 1 (1987) pp 57-77 Bused on the assumption that only axially aligned plies can sustain any load and that all applied shears can be carried as tension and compression forces at 45° to the shear axes, a simple design for laminates is presented and discussed. Stress singularity in composite laminates by finite element method Yeh, J.R. and Tadjbakhsh. I.G. Journal q[ Composite MateriaL~' Vol 20 (July 1986) pp 34 7-364 The stress singularity at the boundary-layer of an interface betwcen adjacent laycrs in a laminated composite was analysed using a compact quasi three-dimensiomd finite clement formulation, based on singularity transformation. The numerical results achieved correlated well with existing analytical solutions. It was concluded that thc boundary layer stress singularity depends only on material properties and fibre orientation of the adjacent layers in a composite laminate and determines the fundamental nature of the boundary layer effects.
COMPOSITES. JULY 1987
Damage in composites-modeling of imperfect bonding Aboudi, J. Composites Science and Technology Vol 28 No 2 (1987) pp 103-128 A mathematical model which incorporates damage due to the imperfect bonding between reinforcing fibres and matrix is presented. The model may bc used to predict overall moduli anti coefficients of thermal expansion.
GENERAL
Delamination growth in angle-ply laminated composites Kim, K.D. anti Hong, C.S.Journal ol'Composite Materials Vo120 (Sepwmber 1986) pp 423-438 The stability of dclamination crack growth in angle-ply laminates subjected to mechanical and thermal loading were analysed using the rule-of-mixtures and the strain-energy release rate concept in linear fracture mechanics. A quasi three-dimensional finite element method was used. The effect of delamination on the tensile strength lbr small fibre angles was also evaluated. The authors conclude that mode 3 is the dominant fracture mode of free edge delamination. Delamination was found to be influenced by fibre orientation, ply thickness, thermal residual stresses (which play a significant role) and loading conditions (tensile/compressive). It was found that thicker laminates delaminate at lower strain levels. The tensile strength results from the present analysis were closer to experimental results than those predicted using the failure criterion for small fibre angles.
Accelerated environmental conditioning of corn posites Lee, W.l., Ciriscioli. P.R. and Springer, G.S. S4MPE Quarterly Vol 17 No 4 (July 1986) pp 27-31 A procedure which has been developed to reduce the time required to perform environmental tests is described. Equations are given which provide the environmental conditions leading to the fastest moisture uptake in the organic matrix and charts are presented from which the conditions for accelerated tests can be obtained. On the analysis and design of the end notched flexure (ENF) specimen for Mode I! testing Carlsson, L.A.. Gillespie Jr, J.W. and Pipes, R.B, Journal q/'('ompo~ite Materials Vo120 (November 1986) pp 594-604 An extension of the beam theory solution to invcstigate the influence of interlaminar shear deformation and friction between the crack surfaces on the strain-energy release rate is presented. The optimum design for an endnotched flexure specimen, to obtain a linear response, is presented. It was [ound that for reasonable coefficients of friction, the error in G u induced by neglecting friction was only 2-4%. "['he influence of the interlaminar shear dclormation may be minimized by using beams with small thickness-to-crack length ratios. Analysis of progressive failure in composites Ochoa, O.O. and Engblom. J.J. ('omposite,s Sciem'e and I~'chnolo,W Vol 28 No 2 (1987) pp ,W-102 An incrcmcnlal failure accumulation technique is presented for angle-ply, cross-ply and uniaxial composite laminates. Piecewise smooth failure criteria that distinguish between lhe failure modes arc implemented in a finite clement analysis. The analytical capability of this progressive failure method which distinguishes between failure modes and traces failure progression to ultimate laminate failure is dcmunstrated for uniaxial tension and fourpoint bending problems. Boundary element study of a loaded hole in an orthotropic plate Mahajcrin, E. and Sikarskie, D.L. Journal Of Composite MuteriaL~ Vol 20 (July 1986) pp 375-389 A boundary element method (BEM) for the analysis of mechanically fastened composites is presented. The traditional BEM method was modified to allow for the determination of boundary stress and displacements. An analytical scheme was developed lbr the evaluation of boundary integrals in elements containing singularities and combined with a special integration quadrature formula for the remaining elements. Accurate results were obtained for the stress concentration factors lbr different hole sizes and various boundary conditions. The method was compared directly with the finite element method.
264
Effect of fibre and matrix maximum strain on the energy absorption of composite materials Farley, (i.L. Journal o[ Composite Materials Vol 20 (July 1986) pp 322-334 The el'feet of fibre and matrix maximum strain at failure on the energy ubsorption of a variety of commercial graphite reinIorccd composites was investigated. Static crushing tests were perlbrmed on chamfered tube specimens and the specific sustained crushing stress was used to compare the energy-absorbing capability of thc different tubes. The crushing characteristics demonstrated that for maximum energy absorption from a particular fibre, the matrix material in the composite must have a greatcr strain at failure than the fibre. The effect of load distribution on the strength of pin loaded holes in laminated eomposites Chang, F.K. Journal o[' Composite MateriaLv Vol 20 (July 1986) pp 401-409 The effect of an assumed cosine load distribution in the inside boundary of the hole, on the calculated strength and predicted failure mode of pin-loaded holes, was compared with the calculated results from a knowledge of the actual displacements on the inside surface of a hole. The strengths and failurc modes calculated by both mcthods were found to agree closely when using the Yamada-Sun failure criterion with the Chang-Scott-Springer characteristic curve. Fibre inclination model of three-dimensional textile structural composites Yang, J.-M., Ma, C.-L., Chou, T.-W. Journal q[' Composites Material.s; Vol 20 (September 1986) pp 472-484 The effective in-plane elastic moduli of threedimensional textile composites were analysed using modified classical laminate plate theory and a fibre inclination model. In this model, the unit cell treats the yarns as being composed of straight segments of an inclincd unicfircctional
laminate oriented in different directions. The results show reasonably good agreement with experimental data.
FTIR characterization of advanced materials Young, P.R. and Chang, A.C. SAMPE Quarterly Vol 17 No 4 (July 1986) pp 32-38 A survey of Fourier transform infrared spectroscopy sampling techniques as applied to resins, fibres, prepregs and composites is presented. Scveral promising specialized FTIR techniques are discussed. The optimal design of symmetric laminated beams considering damping Liao, D.X., Sung, C.K and Thompson, B.S. Journal (?.[Composite Materials Vo120 (Sepwmber 1986) pp 485-501 An experimentally validated analytical model for laminate damping was incorporated into an optimization algorithm to establish a viable design tool to synthesize laminated beams for optimal damping anti stiffness. The thickness of each ply. its location relative to the plane of beam symmetry and the orientation of fibres in each ply wcrc considered. IHustrativc examples tbr several test problems arc presented including the constraint condition of invariable flexural rigidity. Predicting the orientation of short fibres in thin compression mouldings Jackson, W.C., Advani, S.G. and Tucker. C.L Journal of ('omposite Materials Vo120 (November 1986) pp 539-557 A method is presented for predicting the orientation of short, rigid fibres in thin compression moulded parts. The method extends Folgar and Tuckers orientation model to show how a mould filling simulation can be combined with the orientation mode[ to predict the fibre orientation in moulded purls in the presence of non-homogcncous flow fields. A generalized Hele-Shaw modcl was used to predict flow and deformation during mould filling. The results of the calculations compare favourably with experiments on sheet moulding compound and a model suspension of nylon fibres in siliconc oil.
Simple design for reliable high performance laminates Spencer, A.M. Composiws Science and Techno/ogy Vol 28 No 1 (1987) pp 57-77 Bused on the assumption that only axially aligned plies can sustain any load and that all applied shears can be carried as tension and compression forces at 45° to the shear axes, a simple design for laminates is presented and discussed. Stress singularity in composite laminates by finite element method Yeh, J.R. and Tadjbakhsh. I.G. Journal q[ Composite MateriaL~' Vol 20 (July 1986) pp 34 7-364 The stress singularity at the boundary-layer of an interface betwcen adjacent laycrs in a laminated composite was analysed using a compact quasi three-dimensiomd finite clement formulation, based on singularity transformation. The numerical results achieved correlated well with existing analytical solutions. It was concluded that thc boundary layer stress singularity depends only on material properties and fibre orientation of the adjacent layers in a composite laminate and determines the fundamental nature of the boundary layer effects.
COMPOSITES. JULY 1987