CCM 95-35 Abstract
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CCM 95-35
Effect of Processing Variables on Consolidation and Bonding in the
Thermoplastic Fiber Placement Process
N. B. Ersoy, O. Vardar, B. K. Fink, and J. W. Gillespie Jr. (advisor/advisors: name(s))
keywords: Thermal degradation, thermoplastic, fiber placement, bonding
Effects of elevated-temperature exposure during thermoplastic fiber placement
on bonding and consolidation is investigated experimentally for AS4/PEKK
composites. Coupons of 24 layers are consolidated on the University of
Delaware's Center for Composite Materials (UD-CCM) fiber placement robot at
deposition rates of 20 and 40 mm/s over a wide range of process temperatures
(700-900deg.C in 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 build-up are considered: polymer bonding and
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 370deg.C and 0.70 MPa pressure) in order to remove any effect of poor
consolidation on strength. The void content of the robot consolidated panels
ib measured. Short beam shear tests are performed on the specimens cut from
each coupon. Strength and void content measurements of the robot-consolidated
panels are presented to illustrate the effect of processing parameters on
product quality. Results of the short beam shear strength test performed on
reconsolidated coupons indicate that there is a significant decrease in the
strength of coupons consolidated at the 20 mm/s deposition rate, suggesting
that polymer degradation is insignificant at that rate. Experimental values
for the degree of bond and final void content of robot-consolidated panels are
compared with the model-predicted values. Model predictions for degree of bond
are in good agreement with experimental results except for high temperatures at
the 20 mm/s deposition rate, where polymer degradation is expected to occur.
However, the model overestimates the final void content. The effects of void
content on short beam shear tests are discussed.
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