Mechanical properties of titanium alloys with lamellar microstructures and small beta-grain sizes

A high T g thermosetting PMR-type polyimide, designated as DMBZ-15, was developed by replacing methylene dianline (MDA) in PMR-15 with 2,2'-dimethylbenzidine. Polyimide/carbon fiber (T650-35) composites were fabricated from a formulation of 3,3', 4,4'-benzophenonetetracarboxylic acid dimethyl ester (BTDE) and 2,2'-dimethylbenzidine (DMBZ), along with nadic ester (NE) as the endcap. DMBZ-15 displays a higher glass transition temperature (T g = 414 °C than PMR-15 (T g = 345°C), and thus retains better mechanical properties for brief exposure above 400°C. The physical properties and long-term thermo-oxidative stability of the DMBZ-15 polyimide/carbon fiber composites are also compared to that of PMR-15 composites.