Rotationally moulded thermoplastic sandwich composites in small marine leisure craft: Fracture properties and damage analysis of the composite structure

The use of thermoplastic composite structures is increasing in small marine leisure craft as it is more cost effective for large production runs and the material is recyclable. The use of a thermoplastic sandwich composite made using rotational moulding techniques is now being used. A rotational moulding thermoplastic sandwich composite has two skins separated by a thermoplastic foamed core that is manufactured in a single step providing better attachment between core and skin layers than traditional sandwich structures manufactured using thermosets. This paper outlines the work that has been carried out to investigate the damage tolerance of rotationally moulded thermoplastic sandwich composites under impact. A number of samples of different skin-core thickness combinations have been tested under low velocity drop weight impact loading at three different impacted energy levels 20, 30 and 50 J in order to identify the damage at different layers as well as the effect of the core-skin thickness on the impact behaviour of this composite. From the testing it is seen that the stiffness of the sandwich composites increases with foamed core thickness as well as overall thickness of the samples. The skin thickness is found to have more effect to increase the stiffness than the foamed core thickness. Visible plastic deformation was found on the outer surfaces without any crack in the core materials and no delamination was found at skin/core interfaces.