Overview of polymer matrix composites performance and materials development for aerospace applications

We review our present and future studies on the performance characterizatio n and materials development of polymer matrix composites for aero-space app lications. For bismaleimide (BMI) - carbon fiber composites we present the effects of monomer composition and cure conditions upon density, Tg, moistu re diffusion characteristics and composite microcrack initiation and develo pment. Longer cure time at 177 degreesC of eight hours versus standard 1.5 hours results in significant decrease in microcracking formation. For polymide (PI) - carbon fiber composites we report the effects of PI hyd rolytic degradation as a function of time ( 1 - 360 days) and temperature ( 100 - 250 degreesC) upon Tg, mechanical properties and molecular weight on a range of PI's. The kinetics of degradation is characterized in terms of depolymerization to polyamic acid and then the monomers, which are both rev ersible processes, and then the onset of irreversible degradation. The diff erences in the kinetics of AFR700, K3B and PETI 5 PI's are described in ter ms of their molecular structure. Issues related to the performance of polymer matrix composites for cryogeni c fuel tank applications will be addressed and our initial results on the c haracterization of the critical parameters controlling the E-beam cure of e poxies will be presented. The development of low cost carbon fibers and high carbon content complex s haped composites from anthracite powder will be reviewed.