Mode I and Mode II fracture toughness of high-performance 3000 g mole(-1) reactive poly(etherimide)/carbon fiber composites

A phenylethynylphthalic anhydride terminated poly(etherimide) oligomer with a molecular weight of M-n = 3000 g mole(-1) has been synthesized for use i n high-performance composite and adhesive applications. This reactive poly( etherimide) exhibits excellent thermooxidative stability and solvent resist ance upon curing at high temperatures. Towpreg has been produced by coating unsized, G30-500, 12k carbon fiber tow with this oligomer in a powder form . A minimal dry powder prepregging technique was employed for rapid process ing to circumvent the problems associated with high viscosity and to perfor m the operation in an organic solvent-free environment. This towpreg has be en manufactured into flat composite laminates via manual lay-up and hot pre ss consolidation and cure. The Mode I and Mode II fracture toughness of the se composite panels has been investigated via the double cantilever beam (D CB) and end-notch flexure (ENF) test methods. Fracture surface and microstr ucture features are correlated with the measured mechanical properties. (C) 1998 Elsevier Science Ltd. All rights reserved.