KNITTED CARBON FIBER REINFORCED THERMOPLASTICS

Structure-Properties Relations

Abstract

The paper provides an overview over a 4 years research work embedded in the framework of a BRITEEURAM Project. In this study, PEEK and PA12 as matrix systems intermingled with the carbon fiber yarns, either continuous or staple spun yarns, were investigated. Structure-properties relations of knitted fabric reinforced composites were elucidated varying systematically, fiber content, number of knit layers, yarn and matrix properties. The 3-dimensional fiber orientation in the composite was assessed by reconstruction of the bundle geometry from stacked cross sections. Static tensile and bending properties were determined at various angles between wale and course direction indicating a strong correlation between these properties and the respective knit orientation. Fatigue tests revealed a considerable influence of the yarn properties indicating a higher fatigue resistance for staple yarns than for continuous yarns. Fracture mechanical as well as impact failure studies supported the importance of the fiber bundle for the understanding of the properties of the composite and they proved the insensitivity of these materials against delamination and notch effects.