A prepreg comprising at least one layer of carbon fibers and a curable thermosetting resin system, the curable thermosetting resin system at least partly impregnating the at least one layer of carbon fibers, wherein the curable thermosetting resin system comprises: a. a curable thermosetting resin including at least one epoxide group; b. a curing agent for curing the curable thermosetting resin, wherein the curing agent is present in the liquid phase and includes a cyanamide reactive group; c. an accelerator for accelerating the curing of the thermosetting resin by the curing agent, wherein the accelerator includes at least one urea reactive group; and d. a rheology modifier for the curable thermosetting resin system, wherein the rheology modifier is at least one of a thermoplastic resin and an inorganic particulate thickener or a mixture thereof.