Factors influencing face/core crack propagation in PVC foam core sandwich

Fracture toughness of a large range of PVC foam cores was determined using the single edge notch bend (SENB) specimen. Debond fracture toughness for sandwich specimens with the same foam cores was characterized using the TSD specimen. Examination of the crack propagation path in specimens with adequate face/core adhesion revealed that the debonding process occurred by crack propagation in the core, near the face/core interface. It was observed that the debond toughness and core toughness are of similar magnitude although the debond toughness exceeds the core toughness, especially for the higher density cores. Possible reasons for the elevation of the debond toughness over the core toughness such as plastic zone enlargement, mode mixity, core thickness, and gradient of properties of the core are examined. It was found that the plastic zone enlargement is a major factor for increase in debond toughness over the other factors examined.