A prepreg comprising a layer of impregnated reinforcing fibers comprising at least one layer of reinforcing fibers impregnated by a resin composition comprising at least a thermosetting resin, a curing agent and an accelerator, such that the accelerator has a gradient concentration which is more concentrated in the resin composition in the vicinity of the reinforcing fibers than further away. The resin composition comprising a first resin composition impregnates the reinforcing fibers to provide a layer of impregnated reinforcing fibers and a surface layer comprising a second resin composition is formed on the layer of impregnated reinforcing fibers, wherein the first resin composition has at least one peak exotherm occurring at a time earlier than and/or at a temperature lower than any peak exotherm of the second resin composition. The heat generation from the first resin composition is tailored to initiate or speed up the curing of the second resin composition, leading to a substantial reduction of cure cycle time of the prepreg. Excellent handling and processing abilities of the uncured prepreg and excellent physical, thermal and mechanical properties when cured are achieved.