STUDIES OF GEOMETRY-EFFECTS ON STRAIN-ENERGY RELEASE RATE OF COMPOSITE LAMINATE

The width and thickness effects on the strain-energy release rates of composite laminates under uniaxial tension are presented. The influenc e of width on the strain-energy release rate can be ignored only when the width is at least eight times larger than the laminate thickness. For laminates stacked with similar sublaminates, energy release rates decrease with thickness, while for those laminates grouped by like pli es, the energy release rates go up first and then decrease. All the ma ximum energy release rates for different widths fall on the same ratio of thickness/width to which laminate designers should give their atte ntion. A series of comparisons were carried out for strain-energy rele ase rates calculated by the rule of mixtures and finite-element method . By taking the moment resultant into account, the results calculated by the rule of mixtures can be more properly correlated with the strai n-energy release rates. The effect of thickness on the energy release rate of laminates stacked with similar sublaminates can be determined by utilizing the rule of mixtures, but it is not valid for laminates g rouped by like plies. The limitations and applications of the rule of mixtures are discussed in detail.