Failure analysis of marine composite sandwich beams with syntactic foam cores under bending loads

In this work, a progressive failure analysis framework is proposed to investigate the bending failure mechanisms of composite sandwich beams with syntactic foam cores. The numerical framework incorporates the cohesive zone model to simulate interface debonding and adopts Hashin's failure criteria to evaluate damage in composite facesheets. Moreover, a novel crushable foam numerical model considering tension-compression asymmetry is developed for the syntactic foam, where the maximum stress criterion and maximum strain criterion are employed to predict its tensile and compressive failure, respectively. Numerical predictions show good agreement with experimental results and successfully capture the damage initiation and propagation during the bending process. Results demonstrate that the final failure mode consists of facesheet compressive failure, foam tensile failure, and interface debonding. Variations in span length alter the failure process of the sandwich beam, driving the failure behavior to shift from progressive damage accumulation to catastrophic collapse. The numerically constructed failure mechanism maps offer critical insights into the correlation between failure load thresholds and design parameters. Specifically, variations in span length and asymmetric configurations impose remarkable effects on the failure evolution process, while the foam-to-facesheet thickness ratio exhibits minor influence on failure mode.