Analysis of a compressive shear test for adhesion between elastomeric polymers and rigid substrates

A compressive shear test for investigating adhesion between an elastomeric polymer and a rigid substrate has been studied. The test consists of loadin g a specimen comprising of a 3-ply laminate: substrate/polymer/ substrate, in compression and shear at a specified angle to the loading direction. Und er displacement control and when adhesion is sufficiently low, an interfaci al crack nucleates at one interface early during loading and propagates sta bly up to a critical load at which unstable propagation with an associated load drop ensues. The case of an isothennal hyperelastic material has been analyzed by computing the energy release rate for an interfacial crack as a function of crack length. The analysis shows that for a range of initial c rack size interfacial crack propagation is stable until crack length reache s a critical size at which unstable propagation ensues. The energy release rate at this instability is relatively insensitive to angle of loading, str ain, and hyperelastic parameters, which allows one to extract an interfacia l toughness, Gamma(0), from overall measurement of stress and strain. The a nalysis has been extended to consider combined hyperelasticity and viscoela sticity by using a cohesive zone model for crack propagation implemented as a cohesive finite element. The energy release rate and cohesive zone analy ses give identical results for an hyperelastic material. For a viscoelastic -hyperelastic material, the cohesive zone approach allows the viscous losse s in the bulk polymer to be estimated separately from the value of interfac ial fracture toughness. Both analyses have been applied to experiments on g lass/polyvinyl butyral (Butacite (R))/glass laminate specimens. The 'intrin sic' interfacial toughness, consisting of contributions from bond rupture a nd a near-tip process zone, is found to be rate-dependent and lies in the r ange 50-200 J m(-2).