Development and Evaluation of an Alternative Powder Prepregging Technique for Usewith LaRC-TPI/Graphite Composites

摘要

The study investigates an alternative powder prepregging method for use withLangley Research Center Thermoplastic Polyimide (LaRC-TPI)/graphite composites. The alternative method incorporates the idea of moistening the fiber prior to powder coating. The material was subsequently laminated into small coupons which were evaluated for processing defects using electron microscopy. After the initial evaluation of the material, no major processing defects were encountered but there appeared to be an interfacial adhesion problem. As a result, prepregging efforts were extended to include an additional fiber system, XAS, and an semicrystalline form of the matrix. The semicrystalline form of the matrix was the result of a complex heat treating cycle. Using SEM, the fiber/matrix adhesion was evaluated in these systems relative to the amorphous/AS-4 coupons. Of the samples evaluated, the semicrystalline/AS-4 and amorphous/XAS showed improvements relative to the amorphous/AS-4 coupons. Based on these results, amorphous and semicrystalline/AS-4 and XAS materials were prepregged and laminated for transverse tensile testing. Of the samples tested, the amorphous/AS-4 and XAS coupons had average transverse tensile strengths around 33 MPa, and average transverse tensile moduli around 9.3 GPa. The semicrystalline/AS-4 and XAS had a poorer mechanical performance. The average transverse strengths for these samples was approximately 11 MPa. There was a slight improvement in the transverse modulus for the semicrystalline/AS-4 sample but there was no improvement in the modulus for the XAS counterpart. In terms of adhesion, the interfacial adhesion was comparable with previous results.