Effect of Notch Root Radius on the Apparent Fracture Toughness in CNT and Carbon Fiber Reinforced, Epoxy-Matrix Hybrid Composite

Significantly improved fracture resistance (in terms of fracture toughness) can be imparted to monolithic materials by adopting composite design methodology based on fiber and nano particulate reinforcement technology. The present work describes the fracture behaviour of one such reinforced material; in this case, carbon fiber (Cf)- and carbon nanotube (CNT)- reinforced epoxy composite. The Cf and CNT reinforced, epoxy-matrix hybrid composite in longitudinal and transverse orientations with varied finite notch root radii (in the range of 120–750 μm) are subjected to mode-I (tensile) fracture. The fracture toughness/resistance (KQ) of the material is then evaluated and analyzed by investigating the influence of varying notch root radii in longitudinal and transverse orientations. Such an analysis has revealed that the present unidirectional epoxy hybrid composite exhibits a critical notch root radius of 270 μm in longitudinal and 390 μm in transverse orientation.