DEBONDING AND CRACK KINKING IN FOAM CORE SANDWICH BEAMS .1. ANALYSIS OF FRACTURE SPECIMENS

Sandwich beam specimens, recently developed For the study of facing/co re debond fracture, were analyzed using the finite element method. Pee l fracture was approached using a modified double cantilever beam (DCB ) sandwich specimen with a precrack between the facing and core, while shear fracture employed a modification of the ASTM block shear test t o include a facing/core precrack. Complex and conventional stress inte nsity factors were calculated for bimaterial cracks located between fa cing and bondlayer and bondlayer and core over a large range of core m oduli. Overall, much larger stress intensity factors were observed for an interfacial crack between the facing and bondlayer than for a crac k between the bondlayer and core for both types of specimens. Crack ki nking analysis of the DCB specimen revealed that the debond tends to r emain interfacial for stiff core materials, but may deflect into the c ore for compliant core materials. In shear loading of a debonded sandw ich beam it was demonstrated that crack kinking is possible for any co re material.