Peel Adhesion: Rate Dependence of Micro Fracture Processes

Abstract

The micro-fracture mechanism of peeling is studied by means of a “bond stress analyses” which permits direct measurement of the distribution of normal or “cleavage” type stresses localized at the propagating boundary of failure. Improved instrumentation now permits direct stress analysis over nearly three decades of peeling rate. Experimental stress distributions are presented for an acrylic adhesive peeled from stainless steel. This study covers the transition region from elastomeric to flow state response where the viscoelastic transition from apparent interfacial to cohesive failure is observed for this acrylic copolymer. The major features of the cleavage stress distribution are qualitatively interpreted in terms of a cavitation-filamentation model which describes entanglement slippage as the dominant rate factor for cleavage response.