Die-Less Forming of Thermoplastic- Matrix, Continuous-Fiber Composites

A die-less forming process is described which is intended to be an eco nomical method for manufacturing large, complex-shaped components from thermoplastic matrix, continuous-fiber composite materials. The concept is specialized to tapered shapes which are singly curved, long in their straight direction, and of arbitrary variable cross section along their length. An array of universal, computer-controlled rollers generates such shapes from initially flat laminates or stacks of prepreg sheet. Heating and bending of the material are strictly local operations occurring only within a small active zone at any one instant, thereby eliminating the need for fixed tooling and for large autoclaves or presses. The rollers are controlled using a "kinematically admissible bending" algorithm which requires interply sliding only in the local hot zone. Despite the fact that all of the regions not being formed are cold and rigid, the fibers of the composite are not forced to change length. Experimental verification to date includes: (1) rapid, local, through-thickness induction heating of carbon fiber, polymer matrix composite workpieces, and (2) kinematically- admissible bending of preconsolidated thermoplastic matrix laminates to simple singly- curved shapes, using a "near-term demonstration" forming machine. Tension superim posed during such bending operations has been shown to be useful for maintaining good fiber alignment.