Novel tow termination method for delimitation suppression in tapered composite laminates

The manufacture of composites structures with thickness variation via Automated Fibre Placement (AFP) necessitates the sequential termination of prepreg tapes (ply drops). This termination in turn creates localised fibre discontinuities with small pockets of resin in the tapered region ahead of the dropped tapes owing to the discrete ply thickness. These discontinuities can be responsible for early onset of delamination in components, having been shown to adversely affect static and fatigue strengths as well as damage tolerance. Previous methods used to mitigate such effects has involved optimising the locations of the discontinuities relative to one-another or changing the stacking sequence, with most approaches complicating the design process, and none fully suppressing delamination. In this work, a novel tow termination method that tapers the ply end, thus removing the discontinuity in the tapered composite was demonstrated. Its effect on the delamination suppression was experimentally and numerically investigated.