Crush Initiators for Increased Energy Absorption in Composite Sandwich Structures

Sandwich composites loaded in edgewise compression often display low energy absorbing failures due to facesheet debonding and/or buckling-type failure modes. Although crush initiators have been used to trigger progressive crushing in monolithic composites, little research has been performed to investigate the use of crush initiators with sandwich composites. In this investigation, fixture-based crush initiators were evaluated for producing progressive crushing failures and high levels of energy absorption under dynamic edgewise compression loading. Four different sandwich configurations were investigated, fabricated using woven or random mat carbon/epoxy facesheets with foam or balsa wood cores. Results show that the effectiveness of crush initiators is highly dependant upon both the facesheet and core materials used in the sandwich construction. Additionally, the initiation of progressive crushing of a sandwich composite appears to be dependent on the stiffness and strength properties of both the facesheets and core as well as the strength of the facesheet/core interfaces. These findings suggest that a sandwich composite may be designed for enhanced energy absorption through the proper selection of facesheet and core materials and geometries such that high-energy absorbing failure progressions are produced, especially with the application of a crush initiator.