Anti-symmetric laminates for improved consolidation and reduced warp of tapered C-sections

Abstract

This paper challenges the conventional use of symmetric stacking sequences by proposing fully uncoupled anti-symmetric laminates that simultaneously improve consolidation and reduce warp of tapered laminates. A demonstrator C-section laminate with an anti-symmetric stacking sequence has been designed to eliminate coupling between in-plane and out-of-plane deformation. Results are compared with a conventional, symmetric baseline. The two laminate designs were deposited on a male tool using automated fiber placement and final de-bulk and cure were performed in a single autoclave operation. It is postulated that long continuous plies spanning a tapered region can inhibit consolidation in unidirectional material when they are not equidistant from the tool surface. The ply termination strategy of the anti-symmetric laminate mitigates this effect. It has been found that the anti-symmetric demonstrator achieved better consolidation compared with the baseline symmetric demonstrator. The results also show for the first time, that the level of warping exhibited by the anti-symmetric laminate is approximately 50% lower than the symmetric baseline.