An improved methodology of constructing inter-fiber failure criteria for unidirectional fiber-reinforced composites

Based on Mohr?s failure theory and physical mechanisms of unidirectional (UD) fiber-reinforced composites, an improved methodology of constructing inter-fiber failure (IFF) criteria is proposed. The expression of the failure criteria is a quadratic polynomial, in which the variables are the normal and shear stress components (an, Tnl, Tnt) on the potential failure plane. The coefficients of the quadratic polynomial are independent of empirical parameters and calibrated only by four basic strengths of a UD composite, i.e. transverse tensile and compressive strengths, Yt and Yc, as well as transverse and longitudinal shear strengths, S23 and S21. It avoids some deficiencies of the previous criteria for IFF in which some parameters may need to be determined by multiaxial stress tests or by empirical data-fitting operation. Compared with the theoretical prediction results and the experimental data of various UD composites, the present IFF criteria show good prediction accuracy.