Abstract: The present invention relates to a hybrid prepreg having reinforcing carbon fibers and foreign fibers. The carbon fibers have a diameter ranging from 5-30 microns and are unidirectionally arranged. The foreign fibers are composed either of single monofilaments having a diameter ranging from between about 50-150 microns or of strands formed by bundling together a plurality of single monofilaments having a diameter ranging from between about 5-50 microns. If strands are employed, they have a conversion diameter (D.sub.0) which is less than about 500 microns. The conversion diameter (D.sub.0) is represented by the following equation: ##EQU1## wherein n is the number of monofilaments used in forming the strand, and wherein d is the diameter of these monofilaments. Examples of foreign fibers which can be used when practicing this invention include boron fibers, metal fibers and organic fibers.

Abstract: An epoxy resin composition useful as a matrix for fiber-reinforced composites is disclosed which includes a mixture containing 30-95% by weight of a tetrafunctional epoxy resin, 3-40% by weight of an admixture of trifunctional epoxy resin oligomers and 2-50% by weight of a bisphenol A epoxy resin having a number average molecular weight of 450-1,300 and such a weight average molecular weight as to provide a ratio of the weight average molecular weight to the number average molecular weight of 1.3-3.0.

Abstract: The present invention relates to a hybrid prepreg having reinforcing carbon fibers and foreign fibers. The carbon fibers have a diameter ranging from 5-30 microns and are unidirectionally arranged. The foreign fibers are composed either of single monofilaments having a diameter ranging from between about 50-150 microns or of strands formed by bundling together a plurality of single monofilaments having a diameter ranging from between about 5-50 microns. If strands are employed, they have a conversion diameter (D.sub.0) which is less than about 500 microns. The conversion diameter (D.sub.0) is represented by the following equation: ##EQU1## wherein n is the number of monofilaments used in forming the strand, and wherein d is the diameter of these monofilaments. Examples of foreign fibers which can be used when practicing this invention include boron fibers, metal fibers and organic fibers.

Abstract: A two component-type curing agent composition is disclosed which comprises a first curing agent which is capable of cross-linking an epoxy resin and which is at least one member selected from primary amines, phenolic compounds and acid anhydrides, and a second curing agent which is at least one compounds represented by the following general formula: ##STR1## wherein X is --CR.sub.1 R.sub.2 --, --CO--, --COO--, --SO.sub.2 --, --SO--, --S--, --O--, --NR.sub.1 --, --SiR.sub.1 R.sub.2 -- or --POR.sub.1 -- where R.sub.1 and R.sub.2 each stands for hydrogen, a lower alkyl or a phenyl; Y and Y' each stands for hydrogen, a lower alkyl or an electron attracting group; R is a lower alkyl; and m and n each is an integer of 1-4.

Abstract: A new thermosetting resin composition is disclosed which comprises a Bisphenol A-type epoxy resin having a number average molecular weight of smaller than 650 but not smaller than 450 and a ratio of the weight average molecular weight thereof to the number average molecular weight thereof of in the range of 1.3-3.0; and a curing agent capable of cross-linking the epoxy resin. The curing agent is preferably a compound represented by the following general formula: ##STR1## wherein X is --CR.sub.1 R.sub.2 --, --CO--, --COO--, --SO.sub.2 --, --SO--, --S--, --O--, --NR.sub.1 --, --SiR.sub.1 R.sub.2 -- or --POR.sub.1 -- where R.sub.1 and R.sub.2 each stands for hydrogen, a lower alkyl or a phenyl; Y and Y' each stands for hydrogen, a lower alkyl or an electron attractive group; R is a lower alkyl; and m and n each is an integer of 1-4, or a mixture thereof with a primary amine, a phenolic compound or an acid anhydride.

Abstract: A new thermocurable composition is disclosed which comprises a Bisphenol A-type epoxy resin having a number average molecular weight of 650-1300, 10-40% by weight of the Bisphenol A-type epoxy resin having an epoxy equivalent of 180-195; and a curing agent capable of cross-linking the epoxy resin. The curing agent is preferably a compound represented by the following general formula: ##STR1## wherein X is --CR.sub.1 R.sub.2 --, --CO--, --COO--, --SO.sub.2 --, --SO--, --S--, --O--, --NR.sub.1 --, --SiR.sub.1 R.sub.2 -- or --POR.sub.1 -- where R.sub.1 and R.sub.2 each stands for hydrogen, a lower alkyl or a phenyl; Y and Y' each stands for hydrogen, a lower alkyl or an electron attractive group; R is a lower alkyl; and m and n each is an integer of 1-4, or a mixture thereof with a primary amine, a phenolic compound or an acid anhydride.