Axial compressive properties of randomly distributed discontinuous long-carbon fiber reinforced themoplastic matrix composite

Planar randomly fiber reinforced composites are of interest in certain structural applications because they have some advantages: (1) they can provide stiffness and strength for multiple load directions; (2) they have ease of fabrication of complex components. The use of randomly distributed discontinuous long-CFRTP has the potential to lead to significant cost savings over continuous CFRP or CFRTP as automated manufacturing methods can be more easily employed. Moreover, high levels of automation lead to more consistent part quality and reduced cycle times, therefore lending these composites to high volume manufacture processes Mechanical characterizations of random composites are required to design structural components from these materials. The potential of the randomly distributed discontinuous long-CFRTP has not been fully recognized in the fiber composite technology community as yet. In the present study, the axial compressive properties of the randomly distributed discontinuous long-CFRTP were investigated. The stress-strain curve shows large non-linear behaviour. The axial compressive modulus of 24.9 (in-plane) and 9.7 (through-thickness) GPa. The axial compressive strength was 211 (in-plane), and 144 (through-thickness) MPa. The results clearly indicate that there are large scattering of axial compressive modulus and strength. The failure morphology for the specimens oriented in-plane and through-thickness directions is significantly different. The specimens oriented in-plane directions show cracks propagating through the kinking of the load-aligned tows and matrix cracking (delamination or splitting). The specimens oriented through-thickness directions show the deformation mode with plies extruding out of the free surfaces of the specimen perpendicular to the fiber direction.