Statistical Theory of Strength of Laminated Composites

Abstract

A statistical theory for the strength of laminar composites is presented. The tensile strength of a laminate is closer to the ideal strength of the sheet material than individual sheets. This is be cause the effects of bad flaws, which drastically lower the strength of single sheets, are substantially reduced in a laminate. The strength enhancement may be as high as 50% for a laminate with as few as five sheets. The theory also shows the dependence of strength on such factors as sheet dimensions and glue shear strength. The essential features of the theory have been con firmed by experiment. The work suggests that the results are not restricted to uniaxial stress. They may be applied to optimize the biaxial and multi-directional tensile strength properties of the laminated material.