Low velocity impact of marine composites: Experiments and Theory

This chapter seeks to provide an overview on the dynamic behavior of Navy-relevant composite materials to low velocity impact, at room and extreme temperatures. The study focuses on carbon fiber laminates toward establishing a compelling body of empirical results, which could support numerical and semi-empirical models for the prediction of dynamic behavior. Experiments were carried out using a modular falling weight tower with a thermal chamber, for different energy levels. Results were collated in terms of maximum load, penetration extent, absorbed energy, indentation, delamination, and residual strength. The main novelty of the research lies in the experimental scheme which was realized to dynamically load marine panels, across a range of experimental temperatures in the presence of the water simulating realistic operating conditions of marine vessels. The setup is based on a modified falling weight machine, in which an instrumented impactor falls on a clamped specimen, resting upon a water column or it is immersed in it, at a controlled temperature. The effectiveness of two non-destructive techniques (ultra sound and electronic speckle pattern interferometry) in detecting barely-visible and non-visible impact damage was investigated. In agreement with our intuition, the presence of the water was found to critically shape the dynamic loading experienced by the panel. Preliminary insight from a physically-based theoretical model was presented to shed light on the underlying fluid-structure interaction and parametrically investigate the role of geometric and physical parameters on the dynamic response of water-backed panels subjected to low velocity impact.