Electro-mechanical studies of multi-functional glass fiber/epoxy reinforced composites

An experimental study is performed to investigate the electro-mechanical response of three-dimensionally conductive multi-functional glass fiber/epoxy laminated composites under quasi-static tensile loading. To generate a three-dimensional conductive network within the composites, multi-wall carbon nanotubes are embedded within the epoxy matrix and carbon fibers are reinforced between the glass fiber laminates using an electro-flocking technique. A combination of shear mixing and ultrasonication is employed to disperse carbon nanotubes inside the epoxy matrix. A vacuum infusion process is used to fabricate the laminated composites of two different carbon fiber lengths (150 mu m and 350 mu m) and four different carbon fiber densities (500, 1000, 1500, 2000 fibers/mm(2)). A four circumferential probe technique is employed to measure the in-situ electrical resistance of composites under tensile load. Although composites of both carbon fiber lengths showed significant decrease of sheet resistance under no mechanical load conditions, composites of 350 mu m long carbon fibers showed the lowest resistivity of 10 omega/sq. Unlike the resistance values, composites of 350 mu m carbon fibers showed a significant decrease in Young's modulus compared to 150 mu m counterparts. For the electro-mechanical response, composites containing carbon fibers of 150 mu m long demonstrated a maximum value of percentage change in resistance. These results were then compared to both 350 mu m and no added carbon fibers under quasi-static tensile loading.