Fabrication and characterization of three-dimensional PMR polyimide composites reinforced with woven basalt fabric

A PMR polyimide composite reinforced with three-dimensional (3D) woven basalt fabric is fabricated for medium high temperature applications. The PMR polyimide matrix resin is derived from 4,4′-methylenediamine (MDA), diethyl ester of 3,3′,4,4′-oxydiphthalic (ODPE) and monoethyl ester of Cis-5-norbornene-endo-2,3-dicarboxylic acid (NE). The rheological properties of the PMR polyimide matrix resin are investigated. Based on the curing reaction of the PMR type polyimide and the rheological properties, an optimum two-step fabrication method is proposed. The three dimensional fabric preforms are impregnated with the polyimide resin in a vacuum oven at 70 °C for 1 h followed by removing the solvent and pre-imidization. The composites are then consolidated by an optimized molding procedure. Scanning electron microscopy analysis shows that needle shaped voids are generated in yarns and the void volume fraction is 4.27%. The decomposition temperature and the temperature at 5% weight loss of the composite post-cured at 320 °C for 24 h are 440 °C and 577 °C, respectively. The dielectric constant and the dielectric loss of the composite are measured by circular cavity method at 7-12 GHz. The tensile strength and the modulus in the warp direction of the composite are 436 MPa and 22.7 GPa. The composite shows a layer-by-layer fracture mode in three-point bending test. The flexure strength and modulus in the warp direction of the composite are 673 MPa and 27.1 GPa, respectively.