Damage sensing in multi-functional hybrid natural fiber composites under shear loading

A comprehensive experimental study is performed to investigate the electro-mechanical response of jute/epoxy composites for in situ damage detection under in-plane shear loading conditions. By embedding carbon nanotubes (CNTs) in epoxy matrix and also reinforcing carbon fibers (CFs) using electro-flocking process between the jute laminates, a three-dimensional sensory network is generated inside the composites. A parametric study is conducted to examine the effect of two different weight percentages of CNTs (0.025% and 0.1%), two different CFs lengths (150 and 350 mu m), four different CF flock densities (500, 1000, 1500, and 2000 fibers mm(-2)), and two different laminate orientations ((0-0-0-0)(T) and (0-90-0-90)(T)) on the generation of electrical conductive network and its role on damage detection. The electrical resistance values are measured using four circumferential ring probes measurement system. Results indicated that (0-0-0-0)(T) orientation showed 400% improvement in interlaminar shear strength compared to (0-90-0-90)(T) composites. CF flocking between the laminates experienced maximum increase of 50% in shear strength compared to non-flocked composites. For all composite types, there is no change in resistance during the elastic deformation of shear loading. Beyond elastic deformation, the increase in CF length and its density showed similar electrical response. The increase in CNTs concentration and laminate orientations did not show significant change in electrical response under shear loading conditions.