A self-healing smart syntactic foam under multiple impacts

In this study, a shape memory polymer (SMP) based syntactic foam and the foam cored sandwich structures were developed for the purpose of repeatedly self-healing impact damage. The foam was made of shape memory polystyrene, glass microballoon, and multi-walled carbon nanotube. The foam cored composite sandwich plates were prepared per the vacuum assisted resin infusion molding (VARIM) technology. A stress-controlled programming was coupled with the curing process of the sandwich plates for shape fixity. The foam was characterized per TEM, DSC, and flat-wise compression test. The sandwich panels were subjected to seven rounds of impact-healing cycles. C-scan and SEM were used to characterize the impact damage and healing efficiency. The impact response was characterized per the load and energy traces. The impact damaged and healed sandwich specimens were then tested using the compression after impact (CAI) tests to evaluate their residual load carrying capacity. The test results show that the impact damage can be healed under multiple impacts and the impact tolerance and residual strength can be recovered. It is also found that coupling the programming with sandwich curing is an effective way of making the foam smart.