Thermoplastic-particle Interlayer Toughening Technology

Toughening thermoset matrix composites with interlayered thermoplastic particles is an effective method to improve fracture toughness and impact resistance without sacrificing hot/wet properties. Furthermore, transverse strength, fatigue resistance and solvent resistance can also be enhanced. Drapability and tackness of interleaved prepreg is maintained as conventional level. Therefore, interlayer toughened composites are the excellent candidate materials for primary structure of aircrafts.In this paper, composites modified with particle-interlayer were fabricated. Based on the aims of improving compression strength after impact (CAI) and evaluate damage resistance and damage tolerance, Mode II fracture toughness test and quasi-static indentation test (QSI) were conducted. The optimum combination and damage parameters were determined according to experimental results. The toughening mechanisms reveal that interlayer zones, formed by thermoplastic particles and matrix, significantly suppress delamination and absorb amount of fracture energy. The parameters affecting toughening effects were also investigated, which is helpful for future engineering application. A Finite Element Analysis (FEA) was eventually conducted, using Mori-Tanaka model and J-integral, to further explain the toughening mechanisms and fracture behaviour of the particle interleaved composites. The aim of the analysis was to examine the influence of the particle concentration and size, and the interaction between the particle and the crack tip. FEA results indicate that interlayer zones can effectively lower J-integral and stress around the crack tip, and the high stress distribution in the region close to the interface can be the driving force for interfacial failure.