Pergamon zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB J. Mech. Phys. Solids, Vol. 44, No. 11, pp. 1867-1890, 1996 Copyright 0 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved PI1 : SO0225096(96)000504 0022-5096/96 $15.00+0.00 DYNAMIC COMPRESSIVE FAILURE OF FIBER COMPOSITES WILLIAM S. SLAUGHTER,? JIANQIANG FAN? and NORMAN A. FLECK1 t University of Pittsburgh, Mechanical Engineering Department, Pittsburgh, PA 15261. U.S.A. and $ Cambridge University Engineering Department, Cambridge CB2 lPZ, U.K. (Received 17 October 1995 ; in revised.form 18 March 1996) ABSTRACT A model is presented for the dynamic compressive response of polymer matrix fiber composites. The model includes the effects of fiber misalignment and material nonlinearity as well as material inertia. The role of fiber bending stiffness is included via a couple stress formulation. The response of fiber composites to suddenly applied, constant compressive axial load is examined. It is found that under constant load, inertial effects contribute to a reduction in the critical stress for composite failure. This reduction is greatest for composites with long initial fiber imperfection wavelengths. For a given load, there is a range of initial fiber imperfection wavelengths that will result in composite failure. Within this range, there is a preferred wavelength, which results in the shortest failure time. Copyright 0 1996 Elsevier Science Ltd 1. INTRODUCTION Advanced fiber composites have gained widespread acceptance as structural materials. The benefits of high specific strength and stiffness provided by aligned fiber composites are sufficient to outstrip competing cost considerations in weight critical applications. This is currently most evident in the aerospace industry, but fiber composites are also becoming more common in the automotive and sporting goods industries. The mechanisms of failure in composite materials are more complex than in mono- lithic materials. The ability to predict failure accurately for arbitrary loading con- ditions is important for the efficient design of composite structures, particularly since fiber composites often exhibit little deformation before rupture (Hull, 1981). The complexity of composite failure means, however, that an understanding of uniaxial strength of a unidirectional fiber composite does not translate into an ability to predict strength for general loading of a laminated, multidirectional composite-the mechanisms of failure may be different. In addition, imperfections in the fibers and matrix result in large amounts of scatter in composite strength. An understanding of the mechanisms of failure is required to predict failure reliably. This understanding is also needed for the development of composite materials with greater strength. The subject of this paper is the dynamic, axial compressive failure of fiber composites. The motivation is the potential use of composites in submersible hulls, which may be subjected to shock loading. Much attention has already been focused 1867