Composites Part C: Open Access (Aug 2020)
Damage resistance of composite structures with unsymmetrical stacking sequence subjected to high velocity bird impact
Abstract
It is current aerospace standard to design composite laminates using a zero [B]-matrix in order to avoid warpage during manufacturing. A zero [B]-matrix is typical for symmetric laminates, thus making symmetric stacking sequences the preferred choice in aerospace designs. In recent works, unsymmetrical stacking sequences with a zero [B]-matrix have been found and proofed to perform well for low velocity impact if some plies are clustered at the impacted side. In this article, the potential of these unsymmetrical stacking sequences is analyzed for the case of a high velocity bird impact onto a composite rotorcraft structure. Four different stacking sequences were examined: two symmetric laminates made with clustered plies and with dispersed plies and two unsymmetrical laminates one with ply-clustering at the impacted face (LPCI) and one with ply-clustering at the non-impacted face (LPCN). All laminates feature a zero [B]-matrix, but differ in the [D]-matrix. For standard ply thicknesses, all laminates showed comparable damage patterns when subjected to bird impact. For thinner composites, when the [D]-matrix becomes more prominent, some differences were found; however, no stacking sequence was significantly superior to the other ones evaluated.