Effect of basalt fibre hybridization on high velocity impact behaviour of carbon/epoxy composites

The aim of this work is to investigate the effect of basalt fibre hybridization on carbon/epoxy laminates when subjected to high velocity impacts. Four different stacking configurations are studied in order to assess the effect of different lay-ups on impact resistance. Two hybrid configurations are manufactured: in the first one (BCBS) fabrics are stacked as a sandwich-like sequence with carbon fibres as a core and basalt fibres as skins, while in the second configuration (CBCS) the core is made of basalt fibres and the skins of carbon fibres. Not hybridized basalt (B) and carbon (C) composites are also manufactured as reference configurations. The response to high velocity impact tests is assessed through the evaluation of the impact and residual velocities of the projectile and the ballistic limit, calculated using experimental data, is compared with the results given by an analytical method, showing a good agreement. The damage in composite laminates is investigated by destructive (optical microscopy) and non-destructive (ultrasonic phased array) techniques. In addition to high velocity impact tests, also three-point bending tests are performed on undamaged specimens. As a result of basalt hybridization, the ballistic limits of all sandwich configurations are enhanced if compared to those of carbon laminates. Therefore the observed decrease of static mechanical properties, namely flexural strength and modulus, of hybrid composites seems to be largely compensated by improved response to impact. Advantages also come in terms of cost saving, since the basalt fibre is far less expensive than the carbon one.