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Numerical analysis of impact deformation and failure in composite plates
Literature survey Prepared by M.R. Alexander, C. Barren, J. Collins, M.D. Glendenning and A.J. Host)/, University of Sheffield, UK GENERAL Control of interfacial adhesion in continuous carbon and Kevlar fibre reinforced polymer composites Jang, B.Z. Composites Science and Technology Vo144 No 4 (1992) pp 333-349 Cold plasmas of oxygen, nitrogen, argon, ammonia and propylene were used to treat carbon fibre surfaces. A two-component bismaleimide, an epoxy and a model thermoplastic polypropylene resin were used as matrices for composites. The ability of the various plasmas to improve interfacial adhesion between fibres and resin was demonstrated. Increased mechanical keying, improved wettability and chemical bonding are presented as mechanisms of improved adhesion. Plasma-polymerized polypropylene was seen to be capable of improving the compatibility between carbon fibres and a polypropylene matrix. An evaluation of the Iosipescu specimen for composite materials shear property measurement Morton, J., Ho, H., Tsai, M.Y. and Farley, G. L. Journal of Composite Materials Vo126 No 5 (1992) pp 708-750 A detailed study is made of the suitability of the Iosipescu specimen tested in the modified Wyoming fixture. The uniformity of the shear stress in the vicinity of the notch and the effect of non-uniformity in the stress field on strain gauge measurements is investigated using a finite element analysis. It is shown that the position of the load introduction point in relation to the test section and material orthotropy has a large effect on the gauge readings. However, it is also shown that the lack of pure shear has little effect on the measurement of shear modulus. Correction factors are determined for the region occupied by the strain gauges. A comparison between strain gauge readings from one surface and Moir~ interferometry on the opposite face reveals a large sensitivity of some fibre orientations to eccentric loading, leading to spurious stress/strain curves. The inconsistent shear property data found in the literature is attributed to this specimen twisting. The application of this study to improving the reliability and accuracy of shear modulus calculations is discussed, and the implications for shear strength calculations are mentioned. Fatigue damage mechanics of composite materials Part 111: Prediction of post-fatigue strength Spearing, S.M. and Beaumont, P.W.R. Composites Science and Technology Vol 44 No 4 (1992) pp 29~307 This paper presents a damage-based model for post-fatigue notch strength. It is an extension of a model for measuring notch strength in laminated composites. A localized stress distribution at the notch tip damage zone is obtained using a simple finite element analysis. The laminate strength is evaluated from a uniaxial stress failure criterion applied to the 0° axis plies. Residual strength is calculated
462
from the applied loading conditions, specimen geometry and lay-up for (90/0)s, (90/0)2, and (90J0)2s T300/914C carbon fibre/epoxy laminates subjected to tensio~tension fatigue cycling.
Fatigue damage mechanics of composite materials Part IV: Prediction of post-fatigue stiffness Spearing, S.M. and Beaumont, P.W.R. Composites Science and Technology Vol 44 No 4 (1992) pp 309-317 The stiffness of carbon fibre cross-ply laminates containing a notch has been determined theoretically. Appropriate degraded stiffness properties for the damaged areas of the laminate have been deduced from a combination of theoretical and experimental results. A finite element analysis of the notched laminate has been employed, incorporating the degraded stiffness results to predict the overall stiffness. The agreement with experimental work is satisfactory. The influence of interphase regions on local thermal displacements in composites Sottos, N.R. and McCullough, R.L. Composites Science and Technology Vol 44 No 4 (1992) pp 319-332 The influence of the interphase on local thermal displacements in polymer-matrix composites has been studied, the experimental work being concentrated on the development of a scanning micro-interferometer for in situ measurements of thermal displacements at the interphase. Successful measurements have been obtained for specimens containing a single carbon fibre in an epoxy matrix. The thermal displacements of the single fibre specimen were modelled using a three-phase composite cylinder system. A comparison of theoretical and experimental results indicates that matrix properties differ from bulk values near the fibre surface. The data is taken as evidence of a lower glass transition temperature near the interphase. Internal failures in model elastomeric composites Gent, A.N. and Hwang, Y.-C. Journal of Materials Science Vol 25 No 12 (1990) pp 4981-4986 The release rate of strain energy due to the growth of an internal crack in a model composite, consisting of a layer of elastomeric materical bonded between two flat rigid surfaces or rigid spheres, is evaluated by finite element analysis. A crack in the centre of the layer causes about twice the reduction in strain energy caused by an interfacial crack of the same size. It is shown that in thin layers a crack can reach a stable size without causing failure, while in a thick layer once the crack begins to grow it will continue to do so. The results are in agreement with some experimental observations. Linear and non-linear failure analysis of composite laminates with transverse shear Reddy, Y.S.N. and Reddy, J.N. Composites Science and Technology I/ol44 No 3 (1992) pp 227 255 The linear and non-linear (von Karman) first
COMPOSITES. NOVEMBER 1992
ply failure loads of composite laminates subjected to in-plane and transverse loads have been studied using a finite element method. The first ply loads are calculated for a uniformly distributed transverse load, a concentrated transverse load acting at the centre of the plate, and a uniformly distributed inplane edge load for simply supported and clamped boundary conditions. The various predicted failure loads differ from each other by about 35% for linear loads and 50% for non-linear loads, and the failure locations differ randomly. The difference in failure load is great between linear and non-linear for transversely loaded, simply supported laminates and thin plates, but is seen to be small for in-plane loading and thick laminates.
Low-velocity impact response of foam-core sandwich composites Nemes, J.A. and Simmonds, K.E. Journal of Composite Materials Vol 26 No 4 (1992) pp 500-519 Experimental and computational methods are employed to study the low-velocity impact response of foam-core sandwich composites with glass fibre/epoxy face sheets. A linear elastic constitutive model is used for the face sheets and epoxy bond layer, while a constitutive model is used for the foam that accounts for non-linear hardening, plasticity and coupling between volumetric and deviatoric deformation. A finite element method is used to obtain deformation histories for the composites which are compared with the experimental results. Qualitative agreement is observed between the experimental and theoretical results. Mode-coupling of waves in laminated tubes Kohl, T., Datta~ S.K., Shah, A.H. and Rattanawangcharoen, N. Journal of Composite Materials Vo126 No 5 (1992) pp 661~682 The modal and dispersive behaviour of tubes made from fibre-reinforced laminates is studied over a range of frequencies. A combination of a wave proagation method with a finite element technique in the radial direction is used to show the radial variation in the constitutive properties of the laminate tubes. A study is made of the effect of altering the number of plies in a laminate on the propagating models and the coupling between these modes. A detailed study is made of the predominantly longitudinal and predominantly torsional modes. Numerical analysis of impact deformation and failure in composite plates Bogdanovich, A.E. and Iarve, E.V. Journal of Composite Materials Vol 26 No 4 (1992) pp 520-545 Transverse impact by a rigid body on a rectangular composite plate is studied analytically. Displacements, deformation and stresses and impact contact characteristics are calculated. The analysis is performed for graphite/epoxy and organic glass/polymeric adhesive laminated plates. The results show the dependence of contact force on time for several levels of mass and velocity of impactor. The analysis of impact damage zones is presented and the change of failure mode with impactor velocity is also studied.
462
from the applied loading conditions, specimen geometry and lay-up for (90/0)s, (90/0)2, and (90J0)2s T300/914C carbon fibre/epoxy laminates subjected to tensio~tension fatigue cycling.
Fatigue damage mechanics of composite materials Part IV: Prediction of post-fatigue stiffness Spearing, S.M. and Beaumont, P.W.R. Composites Science and Technology Vol 44 No 4 (1992) pp 309-317 The stiffness of carbon fibre cross-ply laminates containing a notch has been determined theoretically. Appropriate degraded stiffness properties for the damaged areas of the laminate have been deduced from a combination of theoretical and experimental results. A finite element analysis of the notched laminate has been employed, incorporating the degraded stiffness results to predict the overall stiffness. The agreement with experimental work is satisfactory. The influence of interphase regions on local thermal displacements in composites Sottos, N.R. and McCullough, R.L. Composites Science and Technology Vol 44 No 4 (1992) pp 319-332 The influence of the interphase on local thermal displacements in polymer-matrix composites has been studied, the experimental work being concentrated on the development of a scanning micro-interferometer for in situ measurements of thermal displacements at the interphase. Successful measurements have been obtained for specimens containing a single carbon fibre in an epoxy matrix. The thermal displacements of the single fibre specimen were modelled using a three-phase composite cylinder system. A comparison of theoretical and experimental results indicates that matrix properties differ from bulk values near the fibre surface. The data is taken as evidence of a lower glass transition temperature near the interphase. Internal failures in model elastomeric composites Gent, A.N. and Hwang, Y.-C. Journal of Materials Science Vol 25 No 12 (1990) pp 4981-4986 The release rate of strain energy due to the growth of an internal crack in a model composite, consisting of a layer of elastomeric materical bonded between two flat rigid surfaces or rigid spheres, is evaluated by finite element analysis. A crack in the centre of the layer causes about twice the reduction in strain energy caused by an interfacial crack of the same size. It is shown that in thin layers a crack can reach a stable size without causing failure, while in a thick layer once the crack begins to grow it will continue to do so. The results are in agreement with some experimental observations. Linear and non-linear failure analysis of composite laminates with transverse shear Reddy, Y.S.N. and Reddy, J.N. Composites Science and Technology I/ol44 No 3 (1992) pp 227 255 The linear and non-linear (von Karman) first
COMPOSITES. NOVEMBER 1992
ply failure loads of composite laminates subjected to in-plane and transverse loads have been studied using a finite element method. The first ply loads are calculated for a uniformly distributed transverse load, a concentrated transverse load acting at the centre of the plate, and a uniformly distributed inplane edge load for simply supported and clamped boundary conditions. The various predicted failure loads differ from each other by about 35% for linear loads and 50% for non-linear loads, and the failure locations differ randomly. The difference in failure load is great between linear and non-linear for transversely loaded, simply supported laminates and thin plates, but is seen to be small for in-plane loading and thick laminates.
Low-velocity impact response of foam-core sandwich composites Nemes, J.A. and Simmonds, K.E. Journal of Composite Materials Vol 26 No 4 (1992) pp 500-519 Experimental and computational methods are employed to study the low-velocity impact response of foam-core sandwich composites with glass fibre/epoxy face sheets. A linear elastic constitutive model is used for the face sheets and epoxy bond layer, while a constitutive model is used for the foam that accounts for non-linear hardening, plasticity and coupling between volumetric and deviatoric deformation. A finite element method is used to obtain deformation histories for the composites which are compared with the experimental results. Qualitative agreement is observed between the experimental and theoretical results. Mode-coupling of waves in laminated tubes Kohl, T., Datta~ S.K., Shah, A.H. and Rattanawangcharoen, N. Journal of Composite Materials Vo126 No 5 (1992) pp 661~682 The modal and dispersive behaviour of tubes made from fibre-reinforced laminates is studied over a range of frequencies. A combination of a wave proagation method with a finite element technique in the radial direction is used to show the radial variation in the constitutive properties of the laminate tubes. A study is made of the effect of altering the number of plies in a laminate on the propagating models and the coupling between these modes. A detailed study is made of the predominantly longitudinal and predominantly torsional modes. Numerical analysis of impact deformation and failure in composite plates Bogdanovich, A.E. and Iarve, E.V. Journal of Composite Materials Vol 26 No 4 (1992) pp 520-545 Transverse impact by a rigid body on a rectangular composite plate is studied analytically. Displacements, deformation and stresses and impact contact characteristics are calculated. The analysis is performed for graphite/epoxy and organic glass/polymeric adhesive laminated plates. The results show the dependence of contact force on time for several levels of mass and velocity of impactor. The analysis of impact damage zones is presented and the change of failure mode with impactor velocity is also studied.