Low pressure process for producing substantially voidless composites

Claim 1

A low pressure method of fabricating substantially voidless filament-reinforced composites comprising the steps of (a) mixing a plurality of monomeric compounds of the formulas: ##STR7## wherein R 1 is a tetravalent aryl radical; R 2 is alkyl or hydrogen and at least two R 2 are alkyl; H.sub.2 N-R.sub.3 -NH.sub.2 ( 2) wherein R 3 is a divalent aryl radical; and ##STR8## wherein R 2 is alkyl or hydrogen and at least one R 2 is alkyl and R 4 is a divalent radical of the formula: ##STR9## wherein R 5 is hydrogen or lower alkyl; and wherein the molar ratio of (1):(2):(3) is N:(N+1):2, wherein N has a value of 1 to 20; (b) applying said mixture as a matrix material to a plurality of filaments; (c) imidizing to fully convert said monomeric compounds to obtain, by condensation polymerization, a prepolymer having a defined melt temperature range; (d) heating said prepolymer to an addition polymerization temperature to effect cure; (e) before reaching said temperature and while in said melt temperature range, applying a pressure of 50-300 psi; and (f) maintaining said pressure during cure.