A solvent-free epoxy resin matrix composition comprising: (a) a liquid epoxy resin or a liquid mixture of epoxy resins, (b) a benzylidenamine compound, (c) an aliphatic or cycloaliphatic primary monoamine and/or disecondary diamine; and (d) a catalytically curing tertiary amine. The epoxy resin matrix composition is used as an impregnating resin to form impregnated fiber composite materials.