The Interfacial Failure of Bonded Materials and Composites

Abstract

Composites and adhesive joints are being increasingly used in modern structures. It becomes very important to characterize the failure in such materials especially at the interface between constituents. This dissertation is focused on interfacial failure in composites and bonded polymers. A short-beam shear fracture approach is developed to measure the mode-II fracture toughness of materials with a preferred interface. This method is more efficient than previous methods due to minimal friction between crack faces. A novel failure criterion proposed by Leguillon (2002) is used to predict crack initiation from notches. This dissertation advances the scope of this criterion to predict failure from notches with a connected interface. Same- and bi-material systems are tested under three-point bending to provide relevant data for verification which is also expected to be a benchmark for future numerical simulations. Finally, the compression-after-impact (CAI) of glass/vinyl ester composites subject to sea water aging is investigated experimentally. A reduced order multiscale computational model is used to explain the damage mechanisms in the composite and to capture the experimental degradation in CAI strength.