Graphite Fiber Reinforced Polyimide Composites

Abstract

Comparatively low-void content, high strength and modulus graphite fiber reinforced polyimide composites were fabricated. Utilizing matrices of Monsanto's Skybond 700 polyimide resin and TRW's P13N polyimide resin and reinforcements of ozone-treated Thornel 40 and 50 graphite fibers, these composites exhibited flexural strengths in excess of 100,000 psi, short-beam shear values in excess of 5000 psi, and void contents as low as 5%. Flexural strength versus time at 600°F is presented for composites of P13N and graphite, Skybond 700 and graphite; P13N and glass; Skybond 700 and glass; and P13N and Morganite II. Short-beam shear strength versus time at 600°F is plotted for a composite of P13N and Morga nite II. The best isothermal heat-aging data was obtained with Sky bond 700 and Thornel 50 (ozone treated) composites. These mate rials showed no short-term loss of flexural strength and demonstrated a 76% retention of the initial room temperature flexural strength after 500 hours at 600°F.