IM7 LARC(TM)-IAX-3 POLYIMIDE COMPOSITES

LARC(TM)-IAX-3 (Langley Research Center(TM)-improved adhesive experime ntal resin-3) aromatic polyimide, based on oxydiphthalic anhydride, 3, 4'-oxydianiline (3,4'-ODA) and 1,4-phenylenediamine (p-PDA), was evalu ated as a matrix for high-performance composites. Four poly(amide acid ) solutions in either N-methypyrrolidone or gamma-butyrolactone, end-c apped with phthalic anhydride to various theoretical molecular weights , were synthesized. Unidirectional prepreg was fabricated from each of the four resins utilizing NASA-Langley's multipurpose prepreg machine . The temperature-dependent volatile depletion rates, the thermal crys tallization behaviour and the resin rheology were characterized. Based on this information, a composite moulding cycle was developed which c onsistently yielded well consolidated void-free laminate parts. Compos ite mechanical properties such as short beam shear strength, longitudi nal and transverse flexural strength and flexural modulus, longitudina l tensile strength and notched and unnotched compression strengths wer e measured at room temperature (RT) and elevated temperatures. Similar properties were obtained independent of the carrier solvent used duri ng matrix resin synthesis. These mechanical properties were superior t o those previously measured for IM7/LARC(TM) IA and IM7/LARC(TM)-IAX c omposites. The enhanced mechanical properties were attributed to the s ubstitution of 25% 3,4'-ODA by p-PDA in the LARC(TM)-IA imide backbone s.