Dynamic Cracking and Energy Absorption in Laminates Containing Through-Thickness Reinforcement

Inertial e4ects in the mechanism of 'bre pullout (or push-in) are examined, with emphasis on how the rate of propagation of stress waves along the 'bre, and thence the pullout dynamics, are governed by friction and the propagation of companion waves excited in the matrix. With a simple shear lag model (assuming zero debond energy at the 'bre/matrix interface), the e4ect of uniform frictional coupling between the 'bre and the matrix is accounted for in a straightforward way. Analytical solutions are derived when the pullout load increases linearly in time. The process zone of activated material is generally divided into two or three domains along the axis of the 'bre. Within these domains, slip in the sense implied by the load, slip in the opposite sense (reverse slip), and stick may be observed. The attainable combinations de'ne three regimes of behavior, which are realized for di4erent material parameter values. The elastodynamic problem is also solved more accurately using a plane stress 'nite element method, with friction represented by an interfacial cohesive zone. The predictions of the shear lag theory are broadly con'rmed. ? 2003 Elsevier Science Ltd. All rights reserved.