Maximizing the interlaminar fracture toughness of thermoset interleaved woven glass fiber laminates

Interleaving is an effective way to increase delamination resistance in composites. However, there exist very few design rules as to the type of resin that should be used for interleaving. The literature would argue that any resin can be used since laminate toughness depends only on the relative interleaf thickness compared to the plastic deformation zone. However, we argue that the choice of resins is critical for the translation of toughness properties. In this work, we use a range of thermoset resins to systematically change the ratio of mechanical properties from fiber matrix to Resin rich layer (RRL). Our results clearly indicate that both the RRL thickness and the resin properties strongly influence the achievable interlaminar toughness. Ultimately, the degree of toughness translation of the RRL is shown to depend on the ratio of the toughness of the two resins. We conclude that a moderate interleaf matrix toughness ratio is fundamental for effective interleaving.