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Vibration studies for symmetrically laminated circular and elliptical plates resting on elastic point supports
at heating rates greater than 2°C min 1. This was shown to be due to a complex interaction of the instrument, sample thermal conductivity, heating rate and modulus above Tg. Despite this, it was thought that the sensitivity of the technique allowed detection of inhomogeneities due to interphase. An investigation of the influence of anisotropy and frequency on damping in short glass fibre reinforced polypropylene Wray, S., Ashton, J.N. and EI-Sobky, H. Composite Structures Vol 15 No 1 (1990) pp 43-60 The measurement of the dynamic modulus and logarithmic decrement of injection moulded, short glass fibre-reinforced polypropylene is described. The logarithmic decrement was measured from the decaying free transverse vibrations of cantilever beam specimens in the frequency range 60 to 250 Hz. The tests were performed at room temperature in a near vacuum to reduce the effect of air damping. The dynamic moduli of the fibre-reinforced specimens have been compared with the upper and lower bounds derived by Gibson and Yau. Micromechanical characterisation of the nonlinear viscoelastic behaviour of resin matrix composites Aboudi, J. Composites Science and Technology Vo138 No 4 (1990) pp 371-386 In this paper a micromechanical analysis is proposed for the determination of the overall response of unidirectional composites with non-linearly viscoelastic resins. The nonlinear behaviour is modelled by the singleintegral constitutive equations developed by Schapery. The method is implemented for the prediction of the non-linear viscoelastic behaviour of unidirectional glass/epoxy and graphite/epoxy composites subjected to various loading conditions. The predicted response is compared with a finite element solution, and good agreement between the methods is shown to exist. Mode I delamination of a three-dimensional fabric composite Byun, J.-H., Gillespie, J.W. and Chou, T.-W. Journal of Composite Materials Vo124 No 5 (1990) pp 497-518
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COMPOSITES. JANUARY 1991
A double cantilever beam specimen of carbon/epoxy (T300/3501-6) orthogonal interlocked fabric composite was analysed by a finite element method. The effect of through-the-thickness fibres on crack driving force as a function of crack length was investigated using the Mode I strain energy release rate. Experimental results for compliance and strain energy release rate showed the finite element analysis to agree well with practice. The z-fibres were shown to reduce the strain energy release rate in comparison with 2D laminates, more so for stiffer fibres. A model for critical load was proposed for Mode I interlaminar fracture of 3D orthogonal interlocked composites requiring fibre properties, architecture, volume fraction and the Mode I critical strain energy release rate for the 2D laminate.
On isotropic laminate configurations Fukunaga, H. Journal of Composite Materials Vo124 No 5 (1990) pp 519-535 Laminated composites with isotropic stiffness characteristics in- and out-of-plane were considered in this paper. A determining method for isotropic and orthotropic laminate configurations was presented with examples of isotropic laminates of 40 plies. Tensile testing and four-point flexure tests were made on the laminate, giving almost isotropic properties. Static compression failure of carbon fibre T800/924C composite plate with a single hole Soutis, C. and Fleck, N.A. Journal o f Composite Materials Vol 24 No 5 (1990) pp 536558 To determine the mechanics of uniaxial compressive failure in a multi-directional unnotched [(+45/0z)3]~ plate, static tests were carried out. Fibre microbuckliog in the 0° plies was found to be the critical damage mode causing failure in the composite. The compression failure of the [(+__45/02)3]s laminates with circular holes was also investigated using X-ray radiography and SEM to observe damage initiation and propagation. A theoretical model was presented for predicting the static strength of unnotched laminates with an acceptable agreement with experimental data.
Strength of tensile loaded graphite/epoxy laminates containing cracks, open and filled holes Eriksson, I. and Aronsson, C.-G. Journal o f Composite Materials Vol 24 No 5 (1990) pp 456-482 This paper uses the damage zone criterion (DZ¢), which is based on fundamental physical principles as opposed to empirically determined constants, to predict the tensile strength of composite laminates containing holes and cracks. The strength of the laminates was predicted on the basis of the unnotched tensile strength and the critical damage zone length, both fundamental parameters. The resultant predictions were accurate for specimens of different configurations and was simple to apply. Time dependent matrix cracking in cross-ply laminates Moore, R.H. and Dillard, D.A. Composites Science and Technology Vol 39 No 1 (1990) pp 1-12 In this paper the authors describe the use of fibre-reinforced poiymers in static and transient environments. Time-dependent damage accumulation in cross-ply laminates, specifically in the form of matrix cracking, is discussed. The results of this study show that certain composite materials may display significant time-dependent damage under quasistatic and creep loads even at room temperature. Vibration studies for symmetrically laminated circular and elliptical plates resting on elastic point supports Narita, Y. and Iwato, N. Composites Science and Technology Vol39 No 1 (1990) pp 75-88 In this paper a free vibration analysis has been carried out for symmetrically laminated circular and elliptical plates resting on elastic or simple point supports. The Ritz method is used, with a power series as a displacement function, to yield a natural frequency equation for the problem. In a numerical study, the natural frequencies and mode shapes are obtained for plates composed of E-glass/epoxy material. The dependence of vibration characteristics on the material constants, spring stiffness and, in particular, the ply stacking sequence is discussed.
72
COMPOSITES. JANUARY 1991
A double cantilever beam specimen of carbon/epoxy (T300/3501-6) orthogonal interlocked fabric composite was analysed by a finite element method. The effect of through-the-thickness fibres on crack driving force as a function of crack length was investigated using the Mode I strain energy release rate. Experimental results for compliance and strain energy release rate showed the finite element analysis to agree well with practice. The z-fibres were shown to reduce the strain energy release rate in comparison with 2D laminates, more so for stiffer fibres. A model for critical load was proposed for Mode I interlaminar fracture of 3D orthogonal interlocked composites requiring fibre properties, architecture, volume fraction and the Mode I critical strain energy release rate for the 2D laminate.
On isotropic laminate configurations Fukunaga, H. Journal of Composite Materials Vo124 No 5 (1990) pp 519-535 Laminated composites with isotropic stiffness characteristics in- and out-of-plane were considered in this paper. A determining method for isotropic and orthotropic laminate configurations was presented with examples of isotropic laminates of 40 plies. Tensile testing and four-point flexure tests were made on the laminate, giving almost isotropic properties. Static compression failure of carbon fibre T800/924C composite plate with a single hole Soutis, C. and Fleck, N.A. Journal o f Composite Materials Vol 24 No 5 (1990) pp 536558 To determine the mechanics of uniaxial compressive failure in a multi-directional unnotched [(+45/0z)3]~ plate, static tests were carried out. Fibre microbuckliog in the 0° plies was found to be the critical damage mode causing failure in the composite. The compression failure of the [(+__45/02)3]s laminates with circular holes was also investigated using X-ray radiography and SEM to observe damage initiation and propagation. A theoretical model was presented for predicting the static strength of unnotched laminates with an acceptable agreement with experimental data.
Strength of tensile loaded graphite/epoxy laminates containing cracks, open and filled holes Eriksson, I. and Aronsson, C.-G. Journal o f Composite Materials Vol 24 No 5 (1990) pp 456-482 This paper uses the damage zone criterion (DZ¢), which is based on fundamental physical principles as opposed to empirically determined constants, to predict the tensile strength of composite laminates containing holes and cracks. The strength of the laminates was predicted on the basis of the unnotched tensile strength and the critical damage zone length, both fundamental parameters. The resultant predictions were accurate for specimens of different configurations and was simple to apply. Time dependent matrix cracking in cross-ply laminates Moore, R.H. and Dillard, D.A. Composites Science and Technology Vol 39 No 1 (1990) pp 1-12 In this paper the authors describe the use of fibre-reinforced poiymers in static and transient environments. Time-dependent damage accumulation in cross-ply laminates, specifically in the form of matrix cracking, is discussed. The results of this study show that certain composite materials may display significant time-dependent damage under quasistatic and creep loads even at room temperature. Vibration studies for symmetrically laminated circular and elliptical plates resting on elastic point supports Narita, Y. and Iwato, N. Composites Science and Technology Vol39 No 1 (1990) pp 75-88 In this paper a free vibration analysis has been carried out for symmetrically laminated circular and elliptical plates resting on elastic or simple point supports. The Ritz method is used, with a power series as a displacement function, to yield a natural frequency equation for the problem. In a numerical study, the natural frequencies and mode shapes are obtained for plates composed of E-glass/epoxy material. The dependence of vibration characteristics on the material constants, spring stiffness and, in particular, the ply stacking sequence is discussed.