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Thermal Degradation Effects on Consolidation and Bonding in the Thermoplastic Fiber-Placement Process
Final rept. Aug 1994-Sep 1995
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
Pagination or Media Count:
Effects of elevated temperature exposure during thermoplastic fiber placement on bonding and consolidation are investigated experimentally for AS 4polyetherketoneketone PEKK composite. Coupons of 24 layers are consolidated on the University of Delaware Center for Composite Materials UD-CCM fiber-placement robot at deposition rates of 20 and 40 mms over a range of process temperatures 700-900 degC, with 50 deg C increments. The main torch and preheater distances and the compaction force are held constant for all coupons. Two competing mechanisms governing strength buildup are considered 1 polymer bonding and 2 degradation. Coupons are sectioned, and one-half of each coupon is reconsolidated in a hot press at conventional processing conditions i.e., 30 min at 370 deg C and 0.70-MPa pressure in order to remove any effect of poor consolidation on strength. Void content of the robot-consolidated panels is measured. Short-beam shear SBS tests are performed on the specimens cut from each coupon. Strength and void-content measurements for robot-consolidated panels are presented to illustrate the effect of processing parameters on product quality. Results of the SBS strength tests performed on reconsolidated coupons indicate that there is significant decrease in the strength of coupons consolidated at 20-mms deposition rate and high torch temperatures, possibly due to polymer degradation, whereas approximately the same value of reconsolidated strength is measured for the 40-mms deposition rate, suggesting that polymer degradation is insignificant at that rate. Effects of void content on SBS tests are discussed.
APPROVED FOR PUBLIC RELEASE