Failure characteristics and multi-objective optimisation of CF/EP composite sandwich panels under edgewise crushing

In this study we design an optimal composite structure for the reinforcement of vehicle components with enhanced energy absorption but reduced weight, based on the evaluation of damage responses and failure modes of composite sandwich panels under edgewise crushing. A numerical model for compressive crushing of the CF/EP composite sandwich panels is then built and validated experimentally. The results demonstrate complete buckling and progressive failure-to-buckling mode of the panels without and with a bevel, respectively. Considering both the bevel angle and effective height, a failure mode map associated with the energy-absorption assessments is established. The panels in sustained progressive failure exhibit remarkably greater specific energy absorption (SEA) than those in buckling failure. A multi-objective optimisation is then conducted using an optimal surrogate modelling technique to ameliorate energy-absorption capability and light-weight efficiency, with the bevel angle and effective height as variables. The resulting optimal panel with the bevel angle of 36.5 degrees and effective height of 27 mm is obtained and is validated experimentally, showing sustained progressive crushing with the favourable SEA of about 50 kJ/kg. A comparative study proves the advantages of the designed CF/EP composite sandwich structures in terms of energy absorption as compared to other composite (sandwich) structures under edgewise crushing.