Hierarchical aerospace epoxy composites of carbon fiber and hyperbranched filler: toughening behavior from nanocomposites to composites

In this work the effect of a glassy hyperbranched polymer (G_HBP), characterized by a Tg higher than room temperature (-77 degrees C), on the mechanical properties of a patented epoxy resin was investigated. To define an optimized filler concentration, three different G_HBP contents were prepared by a solvent-free technique and improvements of fracture toughness compared to the neat matrix (Delta KC - 16 % and Delta GC - 39 %) and to the corresponding laboratory solvent-based procedure. The solvent-free procedure and the found optimal filler content were considered to manufactured long carbon fiber composite samples of both neat and G_HBP loaded matrix later tested and compared in terms of tensile and flexural properties, as well as fracture toughness performance. Mode I and II interlaminar fracture toughness tests were carried out, revealing remarkable increase of both onset and propagation (Delta GIConset - 29 % and Delta GICprop - 53 %) and preserving the GIIC value (Delta GIIC-+ 6 %). Validation tests in compression after impact were also performed and analyzed.

Automated summary

This study investigated the effect of a glassy hyperbranched polymer (G_HBP) on the mechanical properties of an epoxy resin. The results showed that the addition of G_HBP significantly improved the fracture toughness of the resin and maintained good performance in the preparation of long carbon fiber composites. These findings are of great significance for improving the performance of composite materials.