Interfacial fracture in sandwich laminates

A simple test geometry has been developed for characterising adhesion between the composite skin and the lightweight core in a sandwich structure. The test technique has been applied to characterise adhesion in a number of balsa-based glass-fibre-reinforced sandwich structures. A finite-element analysis of the geometry has shown that, for the balsa sandwich structures tested here, the predominant mode of loading is mode I. Tests at low rates of loading have indicated that the interfacial fracture energies associated with several of the sandwich systems is quite high. It has also been shown that prolonged water immersion does not have a dramatic effect on the fracture properties of these glass-fibre-reinforced polyester/balsa sandwich materials. Finally, tests at high loading rates have shown that two of the sandwich materials suffer quite significant reductions in interfacial fracture energy under impact conditions.