DESTRUCTIVE IMPACT DAMAGE ANALYSIS OF GFRP LAMINATES

Impact behaviour of composite laminates represents a very important point to investigate at the aim to introduce these kind of materials as structural components, in large aeronautical and automotive fields. The main problem is the inner non visible damage under low velocity impact conditions. A lot of researchers [1, 2] have investigated about the possibility to know the onset and the propagation damage mechanism. In literature [3], a debate exists about the better approach to face and solve the problem: even if the force parameter is somewhere used, especially for the damage initiation, the energy-based approach results the more efficient one since it gives the possibility to investigate about the different behaviour related to the three major energy terms responsible for the creation of different damages [4]: the energy stored elastically, the energy necessary for the creation of matrix cracks and the last one for the fibre failure. Another point of interest is, so, represented by the possibility to find a way to distinguish the different kind of the damages and to correlate them to the particular energy stored. In the present research, the attention was particularly put on the extension of the delamination in GFRP laminates subjected to low velocity impact conditions, following an energy based approach. What it was tried to in do in this work was to know the exact location of the delamination along the thickness and to correlate it to the impact energy level and the particular fibre layer orientation. The delaminated areas were investigated layer by layer, for different impact energies adopted, by a destructive analysis. Efforts were done at the aim to correlate the area obtained by the addition of the single measured extensions in each layer to the total projected delaminated one. Analysis in the same direction were carried out in order to investigate about the fibre failure mechanism.