The influence of stitching and unconventional fibres orientation on the tensile properties of CFRP laminates

In the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked together with a particular sequence in order to give specific mechanical characteristics. Layers are organized with different angles, different sequences and different technological processes to obtain innovative materials. This paper introduces a new parameter, able to improve mechanical properties of composites. It analyses an unconventional fibres orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of CFRP. Conventional carbon fibres orientation is generally referred to a Cartesian coordinate system, in which fibres are arranging in bundles along different angle orientations respect to the zero lamina. In this paper a polar coordinate system of continue carbon tow is introduced to create specimens as well as complex geometry components in an easy way. Five different configurations are studied: two are classified as traditional composites (unstitched and Cartesian orientation of woven carbon cloth), three are defined as innovative composites (stitched laminates and continue carbon tow organized in polar or Cartesian system). The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon.