Studies on Stress Intensity Factors and Interaction Effects for Orthotropic Materials

Abstract

Composite materials are indispensable in many industries. Thorough understanding of their behavior under load is required for safe and reliable design of the components. The cracking of orthotropic material can occur during manufacturing or service life. The fracture resistance of a component containing cracks is evaluated using stress intensity factors (SIF). newlineThe mixed mode SIF are determined in the present work for newlinei. The cracks emanating from a circular hole in a finite orthotropic lamina subjected to i) uniaxial stress ii) biaxial stress and iii) mixed boundary condition. Modified mapping collocation method is used to study variation of stress intensity factors with i) crack length / lamina width ratio, crack length / hole radius ratio, for various fibre angles and ii) biaxial loading, and mixed boundary condition for fibre angle 00. newlineii. Inclined and / or eccentric crack in a finite orthotropic lamina using boundary collocation method. Variation of SIF with eccentricity in x, y directions, fibre angle, biaxial loading, crack angle is reported. newlineiii. Two interacting cracks in an orthotropic lamina subjected to uniaxial stress. One of the crack is horizontal and located in the centre of the lamina while the other crack is inclined to the first. Here again, boundary collocation method is used. For the given fibre angle, orientations of second crack which result in increase / decrease in SIF as compared to single crack solution are found out. Also, combinations of fibre angle and crack angles that result in crack closure at the second crack tip are reported. newlinev newlineIn order to determine the SIF, stress functions are defined i) representing stress singularity at the crack tips, ii) satisfying governing equations in the domain and iii) satisfying stress free condition on the crack surfaces (this condition is not satisfied in the study of interaction effect of two cracks).