MAINTAINING FIBER ALIGNMENT DURING DIE-LESS FORMING OF THERMOPLASTIC MATRIX COMPOSITES

Abstract

ABSTRACT Die-less forming experiments on continuous-fiber, thermoplastic matrix composites using a new “cluster roller” concept have been conducted. Good fiber alignment can be produced, and this results in reasonably accurate cross-sectional shape and in good longitudinal straightness despite the absence of fixed dies. The mechanism by which the cluster roller maintains fiber alignment appears to be the shear tractions imparted to the workpiece, which help keep the fibers under tension during bending operations. Fiber alignment is affected by the transverse feed per pass. Springback does not appear to a problem. The minor shape deviations which are observed are consistent with small permanent length changes in the non-transverse plies due to the stress gradient from bending, and will probably need to be predicted as part of the control software for the full die-less forming machine (now being designed). Variations in coil-to-workpiece coupling with workpiece position under the induction coil can create a “cold end” problem, which is resolvable by using a variable velocity profile.