Chemorheologically viscosity tailored matrix resin formulations for use in forming prepregs and composite articles are disclosed. These formulations have a specified viscosity profile obtained from a curable matrix resin and an effective amount of a reactive resin curing agent reactive at room temperature and a latent resin curing agent substantially nonreactive at room temperature. The latent resin curing agent is activated upon heating or radiation. The matrix resin formulation is adapted upon formulation to have a viscosity sufficiently low enough to enable the matrix resin to impregnate fibers or broadgoods at room temperature without the necessity for the application of heat or solvent and which, upon standing at room temperature after impregnation into the fibers or broadgoods to form a prepreg composition, rises in viscosity. The matrix resin in the prepreg experiences a reduction in viscosity upon heating to a viscosity minimum sufficiently low to allow the matrix resin to flow and substantially eliminate formation of voids in the composite article from said prepreg yet not so low as to permit excessive bleeding of the matrix resin from the prepreg. With continued heating, the matrix resin in the composite article cures to a hardened or gelled state.

Composite pressure vessels having improved fiber strength translation of the unidirectional, axial, impregnated strand are obtained by a process in which chemorheologically viscosity tailored matrix resin formulations containing surface-active agents or compounds acting as surface-active agents are employed. The use of chemorheologically viscosity tailored matrix resin formulations containing surface-active agents reduces the strength variation of pressure vessels produced from prepregs of the disclosed matrix resin formulations.