On the penetration energy of fibre-reinforced plastics under low-velocity impact conditions

The paper deals with the prediction of penetration energy of fibre reinforced plastics subjected to low-velocity impact. Some results available in the literature are reviewed first, allowing to individuate the main parameters affecting the energy absorbing capacity of a composite laminate. It is shown that, for a given fibre type, the penetration energy is substantially influenced by the total fibre volume and tup diameter, whereas other factors, such as resin type and content, fibre architecture, stacking sequence and orientations, play a secondary role in the phenomenon. Then, an empirical power law equation recently proposed by the authors, from which the penetration energy can be evaluated, is assessed on the basis of experimental data previously published. The results indicate that the exponent of the power law is perhaps independent of the material considered, being practically the same for graphite fibre, as well as glass fibre reinforced plastics, and even for an isotropic material as polycarbonate, prone to extensive plastic yielding before final failure. The formula proposed, useful for in-plane isotropic and moderately anisotropic composites, can also permit the comparison of impact data generated under different impact conditions.