Abstract: Honeycomb fabricated of non-crosslinked polymer is prepared by impregnating a fiber web with a linear prepolymer which is soluble in an organic solvent, and which is readily converted by thermal curing in the absence of a crosslinking agent to an insoluble form with a glass transition temperature exceeding 200.degree. C., preferably exceeding 250.degree. C. The preferred prepolymer is the product of diaminodiphenylsulfone and trimellitic anhydride, and forms a poly(amide-imide) upon cure. A process for forming the impregnated honeycomb is also disclosed, which involves impregnating ribbons or sheets, forming them into stacks bonded together at node lines, expanding the stacks into honeycomb structures, and heat soaking the expanded structures to cure the resin and stabilize the structure.