Crack propagation across an adhesive interlayer in flexural loading

Crack propagation across interlayers separating adjoining brittle plates in flexure was studied using a model glass/epoxy/glass system. A transverse starter crack in the center glass plate was made to propagate to the nearest epoxy interface, where it arrested. System failure occurred at some higher load by crack reinitiation from pre-existing flaws in the adjoining glass surface, not by continuous penetration through the epoxy. A fracture mechanics analysis was developed to elucidate the role of material and geometrical variables.