Measurement of the intrinsic strength and intrinsic and total fracture resistances of stainless steel/E-glass composite joints

Abstract

Parameters that characterize joint fracture are defined and procedures to measure them discussed. The interface strength σ o is measured by using a novel laser spallation experiment, which uses a laser-induced stress wave to separate the interface. The intrinsic (G ir) and total (G or) fracture resistances are measured using double cantilever beam experiments by carrying out these at cryogenic and ambient temperatures, respectively. These experiments are used to obtain hitherto unreported relationships between G or and G ir, and between σ o and G ir, for joints between stainless steel and E-glass composite sections. The durability of the joints under moisture exposure was also studied and was used as a means to alter σ o and G ir. Joint chemistries, including use of silane layers on the steel substrate, are disclosed which optimize the joint performance, with and without the preconditioning treatment of moisture exposure. In such optimized joints, the fracture is always cohesive within the composite adherend. The paper provides quantitative values for G ir, G or and σ o which are useful to a designer to set up the local failure condition in design simulations of ship structures in which such joints are considered as a part.