Journal of the Mechanics and Physics of Solids 51 (2003) 425–460 www.elsevier.com/locate/jmps Dynamic crack growth along a polymer composite–Homalite interface D. Coker a , A.J. Rosakis b , A. Needleman a ; * a Division of Engineering, Brown University, Box D, Providence, RI 02912-9104, USA b Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA Received 11 March 2002; received in revised form 24 July 2002; accepted 30 July 2002 Abstract Dynamic crack growth along the interface of a ber-reinforced polymer composite–Homalite bimaterial subjected to impact shear loading is investigated experimentally and numerically. In the experiments, the polymer composite–Homalite specimens are impacted with a projectile caus- ing shear dominated interfacial cracks to initiate and subsequently grow along the interface at speeds faster than the shear wave speed of Homalite. Crack growth is observed using dynamic photoelasticity in conjunction with high-speed photography. The calculations are carried out for a plane stress model of the experimental conguration and are based on a cohesive surface formulation that allows crack growth, when it occurs, to emerge as a natural outcome of the deformation history. The eect of impact velocity and loading rate is explored numerically. The experiments and calculations are consistent in identifying discrete crack speed regimes within which crack growth at sustained crack speeds is possible. We present the rst conclusive ex- perimental evidence of interfacial crack speeds faster than any characteristic elastic wave speed of the more compliant material. The occurrence of this crack speed was predicted numerically and the calculations were used to design the experiments. In addition, the rst experimental observation of a mother–daughter crack mechanism allowing a subsonic crack to evolve into an intersonic crack is documented. The calculations exhibit all the crack growth regimes seen in the experiments and, in addition, predict a regime with a pulse-like traction distribution along the bond line. ? 2003 Elsevier Science Ltd. All rights reserved. Keywords: Dynamic fracture; Intersonic crack speed; Interface fracture; Bimaterials ∗ Corresponding author. Tel.: +1-401-863-2863; fax: +1-401-863-1157. E-mail address: needle@engin.brown.edu (A. Needleman). 0022-5096/03/$ - see front matter ? 2003 Elsevier Science Ltd. All rights reserved. PII:S0022-5096(02)00082-0