Interfacial fracture in sandwich laminates

A simple test geometry has been developed for characterising adhesion betwe en the composite skin and the lightweight core in a sandwich structure. The test technique has been applied to characterise adhesion in a number of ba lsa-based glass-fibre-reinforced sandwich structures. A finite-element anal ysis of the geometry has shown that, for the balsa sandwich structures test ed here, the predominant mode of loading is mode I. Tests at low rates of l oading have indicated that the interfacial fracture energies associated wit h several of the sandwich systems is quite high. It has also been shown tha t prolonged water immersion does not have a dramatic effect on the fracture properties of these glass-fibre-reinforced polyester/balsa sandwich materi als. Finally, tests at high loading rates have shown that two of the sandwi ch materials suffer quite significant reductions in interfacial fracture en ergy under impact conditions. (C) 1999 Elsevier Science Ltd. All rights res erved.