Mode III Loading of Composite Panels

Abstract

Efficient design of modern aircraft requires an understanding of the mechanical behavior of carbon fiber panels under both in-plane and out-of-plane loading conditions. Currently, relatively little published literature exists for out-of-plane shear (mode III) loading. This paper presents both experimental and computational results for strain fields showing damage initiation, and propagation of notched carbon fiber panels under mode III loading. Experimentally, strain fields were measured using digital image correlation. Computationally, the commercial finite element package Abaqus, using typical composite analysis techniques, was used to calculate strain fields. Comparisons were made between measured and calculated values. Experimental results indicated that areas of both tensile and compressive strain concentrations existed at the notch tip. Damage initiation occurred in these areas, typically only in one or the other. Subsequent damage propagation occurred both in areas of elevated tensile strain and in areas of elevated compressive strain. Computational results showed differences of typically to as compared with experimental results for notch tip strain concentrations before damage and with larger differences after damage had occurred. Overall, these results provide information on how notched carbon fiber panels behave under mode III loading and the effectiveness of a commonly used computational approach in predicating this behavior.