PROCESSING AND PROPERTIES OF IM7 PETI COMPOSITES/

A phenylethynyl terminated imide (PETI) oligomer from the reaction of 3,3',4,4 '-biphenyltetracarboxylic dianhydride, an 85:15 molar ratio o f 3,4'-oxydianiline and 1,3-bis(3-aminophenoxy)benzene and 4-phenyleth ynylphthalic anhydride as the end-capper at a theoretical number avera ge molecular weight (Mn) of similar to 5,000 g/mol was evaluated as a composite resin matrix. Unidirectional prepreg was made by coating an N-methylpyrrolidinone solution of the amide acid oligomer onto unsized IM7. The thermal and rheological properties and the solvent/volatile depletion rates of the amide acid/NMP system were determined. This inf ormation was used to successfully design a molding cycle for composite fabrication. Composites molded under 1.38 MPa at 371 degrees C consis tently yielded good consolidation as measured by C-scan and optical ph otomicrography. Composite mechanical properties at various temperature s included short beam shear strength, flexural strength and modulus, l ongitudinal compression strength and modulus (IITRI), longitudinal ten sile strength and modulus and open hole compression (OHC) strength. Th ese composites exhibited excellent resin dominant properties. The OHC strength values, in particular, suggested that PETI composites have ex cellent damage tolerance.