Design of the Face/Core Interface for Improved Fracture Resistance

This study investigates the face/core fracture behavior of sandwich specimens with different designs. The traditional interface with a quadraxial mat directly adhered to the foam core is compared to interfaces where an additional mat with randomly oriented fibers is inserted between core and face. The extra mat affects the crack propagation path in the sandwich specimen, and makes it more likely for the crack to propagate at or near the interface, instead of kinking into the laminate or core. Further, the extra mat acts as a source for fiber bridging, and hereby the fracture resistance is increased as bridging fibers shield the crack tip from the loading. Results show that the increase in fracture resistance due to fiber bridging is significant. Cohesive laws regarding cracking of sandwich interfaces are extracted.