Compressive characteristics of foam-filled composite egg-box sandwich panels as energy absorbing structures

This paper describes compressive tests on foam-filled composite egg-box panels which were carried out to assess their performance as energy absorbers. Material type, number of plies and stacking angle were varied. Stacking sequences of CFRP [0]nT, CFRP [45]nT (n = 3, 4) and GFRP [0/90]S, [±45]S were used for foam-filled egg-box cores. Fracture modes of representative composite egg-box cores without foam, including crack initiation and propagation, were observed and analysed by multiply-interrupted compressive tests using transparent acrylic face plates on both sides of the egg-box core. The concept of premature buckling of the foam-filled egg-box panels is used to explain the small initial stress peak. Finally, the collapse curve of the core was used to estimate energy absorption capacity. It was found that the foam-filled composite egg-box sandwich panels had a good energy absorption capacity with a stable collapse response resembling the ideal energy absorber.