Abstract: A phenol resin-impregnated sheet formed by impregnating a porous resin sheet with a phenol resin having a degree of cure of from 70% to 95% is arranged on and lamininated to the surface of a carbon fiber-reinforced thermosetting resin sheet. The thickness of the phenol resin impregnated sheet is between 0.01 mm and 1.0 mm. A very even, strong and water-proof wood reinforcing material is obtained. The wood reinforcing material is intergrated and cured on the surface of the wood material by the phenol resin-impregnated sheet to reinforce wood material (single board or bonded board) to form a reinforced wood material. The wood reinforcing material adheres suitably with the wood material and does not cause environmental contamination.

Abstract: The first group of the present invention is a wood reinforcing carbon fiber prepreg, which is produced through impregnation with a mixture resin at a viscosity of 3 to 150 poises at 20° C., wherein the mixture resin contains one or more resins selected from resorcinol based resins and resol type phenol based resins, formaldehydes as curing agents and inorganic acids or organic acids as curing catalysts. The first group of the present invention is a wood reinforcing carbon fiber prepreg having a longer usable time and being capable of imparting the rigidity and elastic modulus of carbon a fiber to the wood to be reinforced at a high ratio. The second group of the present invention is a wood reinforcing carbon fiber prepreg attached wood based sheet, wherein a wood based sheet of a thickness of 0.01 mm to 0.06 mm is arranged on at least one face of a carbon fiber prepreg sheet produced through impregnation with a mixture resin containing a thermosetting resin and a curing agent or a curing catalyst.