Strengthening of L-shaped composite laminates using carbon nanotube reinforcement and thin ply non-crimp fabrics

Arca, Miray Aydan
The advances in manufacturing technologies have increased the use of composite materials in complex shapes such as curved beams. However, use of composites in complex geometries creates a weakness at the curvature and causes delamination failure. Major objective is to provide solution for this problem without degrading properties or increasing the weight of the structure. In this study, the effect of CNTs in the resin and the use of non-crimp fabric on the fracture toughness and curved beam strength of laminates are investigated experimentally. Curved beam composite laminates were subjected to four-point bending loading according to ASTM D6415. Double cantilever beam (DCB) tests and end notch flexure (ENF) tests were conducted to determine mode-I and mode-II fracture toughness, respectively. In the first part, mode-I and mode-II fracture toughness of 3% CNT added laminates are found to be 25% and 10% higher, respectively, compared to prepreg-fabric laminates. However, detrimental effect on the curved beam strength was found. In the second part, changing the material type from unidirectional to thin-ply non-crimp fabric material increased the mode I, mode II fracture toughness and curved beam strength of the laminates. It is observed that the manufacturing defects are the potential failure initiation sides.