Carbon-and Glass-Fiber Knits for Thermoplastic Composites in Cars

Knitted high performance fibers as reinforcement are interesting for loaded parts, due to their drapability and the possibility of waste free near net shape production methods. Additionally, a considerable advantage is seen in the coherence of the knit structure, which prevents uncontrolled fiber flow during thermoforming processes and allows strain hardening and strain stiffening during controlled drawing. Compared to common composite manufacturing processes, this may lower costs.

The knit structure allows an adjustable anisotropy of the mechanical composite-properties due to its drawability. It has been shown that the rate of drawing and the mechanical anisotropy have a linear correlation. Specific weakening of the fiber-matrix interface revealed a dependence of fiber-matrix adhesion on the failure behavior.

Two advantageous manufacturing techniques for advanced composite processing were studied for knitted fiber reinforced thermoplastics: net- shape pressing and organo sheet deep drawing.