Low temperature impact of composite hull wall with floating rigid body

An experimental activity conducted in order to assess the impact behavior, at room and low temperature, of laminates used in the shipbuilding industry, was reported. The conditions which reproduce the impact of a hull at low temperature with a solid body suspended in the water was reproduced. A test equipment was designed and realized to reproduce the real material behaviour in water to obtain a load distribution on the entire surface of the specimen. The results were obtained impacting the laminates placed between the cilyndrical steel impactor and the bag containing water. A falling weight machine equipped with an instrumented steel impactor and a thermal chamber was adopted for the experimental tests. Laminates made by vinyl ester matrix and carbon fibres were considered during the tests, and the results in terms of impact behaviour in hostile environments were compared to what obtained at room temperature. The data obtained under a distributed load were also compared with the results of impacts at concentrated loads

Low-velocity impact behaviour of fibreglass-aluminium laminates

Low-velocity impact tests were performed on fibreglass–aluminium composites made of 2024 T3 sheets and S2-glass/epoxy prepreg layers, using an instrumented falling weight machine. For comparison purposes, similar tests were carried out on monolithic 2024 T3 sheets of equivalent thickness. In the tests, the impact speed, mass, and energy were varied, to ascertain the influence of these parameters on the material response. From the results obtained, the overall force–displacement curve only depends on the impact energy, rather than on the mass and speed separately. Further, the energy required for penetration is higher for monolithic aluminium than for the fibreglass– aluminium. However, the latter material seems to offer better performance than carbon fibre- and glass fibre-reinforced laminates in terms of penetration energy, damage resistance, and inspectability. The main failure modes of fibreglass – aluminium were assessed by both ultrasonic C-scan and chemical grinding of aluminium sheets. It was found that the energy required for first failure is very low, whereas the energy level resulting in first fibre failure is similar to that inducing first cracking in the 2024 T3 sheets. From the experimental data, simple empirical relationships were found for the calculation of maximum contact force, energy, and residual displacement as a function of the maximum displacement