Influence of the manufacturing process on the interlaminar tensile strength of thick unidirectional continuous epoxy/carbon fibre composites

Racing yachts that fly over the sea level use appendices called hydrofoils made out of carbon fibre reinforced plastics. This study discusses the influence of the manufacturing process on their interlaminar tensile strength (ILTS). Indeed, ILTS is a key design parameter, since tensile out-of-plane stresses in the hydrofoil elbow may cause the structure to fail by delamination. Hydrofoils are usually manufactured by traditional hand lay-up and more recently by automated fibre placement technology (AFP). Thick unidirectional L-beam specimens were manufactured from the same prepreg material, either by AFP or by hand lay-up (MAN). AFP specimens were 40 % stronger than MAN ones. The investigation of failure locations as compared to estimated ones made us highlight that AFP specimens reach their highest possible strength while MAN specimens fail prematurely, due to manufacturing-induced defects, such as localised porosities. The key features of AFP technology, with respect to the traditional MAN process, are eventually discussed.