DIE-LESS FORMING OF LARGE AND VARIABLE-RADII OF CURVATURE IN CONTINUOUS-FIBER THERMOPLASTIC-MATRIX COMPOSITE-MATERIALS

Die-less forming is a method of forming complex shapes in continuous-f iber thermoplastic-matrix laminates under only software control, i.e., without fixed dies. The ''continuous'' die-less forming concept for t hermoplastic composite laminates has been extended to encompass (a) co nstant-curvature parts having curvature larger than the forming roller s, and (b) variable-curvature parts. Shape accuracies of 0.016 '' have been attained. Prior work with the same process indicates that aircra ft quality (<6 dB ultrasonic loss) can also be maintained throughout t he operations. The key to good shape accuracy and quality is maintenan ce of a substantial (e.g., 25 degrees C) temperature gradient from the main part of the forming zone to the tangent point where the material exits this zone. Manipulation of advective heat transport by proper s election of the forming velocity was effective in maintaining this tem perature gradient. Key internal behavior which governs the shape accur acy includes adequate interply sliding within the forming zone and avo idance of plastic bending outside of it. This work contributes to meth ods for forming continuous-fiber thermoplastic composites to final net shapes without dies.