Hybrid prepreg containing carbon fibers and at least one other reinforcing fiber in specific positions within the prepreg

A thin hybrid prepreg having a thickness ranging from between 80-200 .mu.m, said prepreg comprising:

• (a) a plurality of foreign fibers, wherein each foreign fiber is in the form of either a single monofilament having a diameter ranging from between 50-150 .mu.m or a strand formed by bundling together a plurality of monofilaments each having a diameter ranging from between 5-50 .mu.m, said strand having a conversion diameter (D.sub.0) less than 500 .mu.m, the conversion diameter (D.sub.0) being represented by the equation ##EQU4## wherein n is the number of said monofilaments employed in making the strand, and wherein d is the diameter of the monofilaments employed in forming the strand;
• (b) a plurality of reinforcing fibers, wherein each reinforcing fiber has a diameter ranging from between 5-30 .mu.m, and wherein each reinforcing fiber comprises carbon fibers which are unidirectionally arranged on one side of the prepreg and glass fibers which are arranged on the other side of the prepreg, said glass fibers being aligned in the same direction as said carbon fibers;
• and
• (c) a thermosetting matrix resin with which said plurality of reinforcing carbon fibers and said plurality of foreign fibers are impregnated,
• said plurality of foreign fibers are at least one kind of fibers selected from the group consisting of boron fibers, metal fibers and organic fibers, said plurality of foreign fibers are spaced at fixed intervals and are arranged in the same direction as the direction of said reinforcing carbon fibers, and said foreign fibers are positioned approximately at the center of the resulting hybrid prepreg.