Improving the Impact Behaviour of Structural Foams

Injection moulded thermoplastic foams, which are always structural foams, combine the versatility of thermoplastic materials with substantial material and energy savings. Through different studies, it has been demonstrated that their mechanical properties can be improved through the control of the foam morphology. In a study conducted at the IKV, several foam morphologies have been prepared and their impact properties have been studied through instrumented puncture tests. Both an amorphous material and a semi-crystalline material have been evaluated. The force vs. displacement curves have been obtained for each material and the properties of maximal impact force and energy absorbed have been correlated with the morphological parameters of skin thickness, cell size and foam density. The results show that the absorption capabilities of the foam can be substantially improved if the foam morphology is controlled. Furthermore, the foam structure affects the fracture behaviour during impact.