Vacuum infusion of a composite E-glass vinylester laminate for nautical application: experimental response to repeated impacts.

The aim of this paper is to investigate the response to repeated impacts of a non-symmetric glass fibre reinforced laminate. The laminate is intended for a nautical application and the manufacturing technique is vacuum infusion. In a first part of the work, four impact velocities (1.566 m/s, 2.215 m/s, 3.132 m/s and 3.836 m/s) were considered, and a minimum of four specimens for any given velocity were subjected to forty repeated impacts or up to perforation. The impact response was evaluated in terms of damage progression by visual observation of the impacted specimens, evolution of the peak force and of the bending stiffness with the number of impacts and by calculating the damage degree (ratio between the absorbed energy and the impact energy). In a second part of the work, additional single impact tests were performed at 4.429 m/s and 6.264 m/s to investigate the laminate strain-rate sensitivity. Repeated impact tests pointed out that the delamination area grows very rapidly in the first few impacts to then level off, following closely the behaviour of the bending stiffness against the number of impacts. The value of the peak force increases in the first few impacts due to compaction and strain-hardening of the resin with a related decrease of the damage degree. Comparison between quasi-static penetration tests and impact tests demonstrates a strain-rate dependency of the laminate bending stiffness and first damage load. The values of R-2 show a good fitness of a linear function on the experimental data.