Failure of CFRP airframe sandwich panels under crash-relevant loading conditions

Abstract

New aircraft fuselage concepts have to prove equivalent crashworthiness standards compared to conventional metallic fuselages for certification. Brittle failure mechanisms of CFRP structures make the verification of equivalent crashworthiness for novel CFRP fuselage concepts challenging since conventional metal fuselages absorb a significant part of the kinetic energy by plasticization. In this context, the damage initiation and failure of twin-walled fuselage panels were investigated under crash relevant bending compression loads. Since the sandwich failure is initiated by core failure, a trigger concept for CFRP composite sandwich panels was developed based on local modifications in the fold pattern of the core for controlled failure initiation. By locally adjusting the collapse strength of the core in normal direction, the failure position and failure load can be adapted according to the defined kinematic hinge requirements. The core trigger concept was validated in experiments with triggered and untriggered sandwich panels under identical loading conditions.