Pre-impregnated composite material (prepreg) that can be cured/molded to form aerospace composite parts that are designed to tolerate hot and wet conditions. The prepreg includes fibers and an uncured resin. The uncured resin includes an epoxy component that is a combination of a trifunctional epoxy resin, a tetra functional epoxy resin and a solid epoxy resin. The resin includes polyethersulfone and a thermoplastic particle component. The uncured resin also includes a curing agent.