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 threedimensional 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 mm and 350 mm) 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 mm long carbon fibers showed the lowest resistivity of 10 X/sq. Unlike the resistance values, composites of 350 mm carbon fibers showed a significant decrease in Young's modulus compared to 150 mm counterparts. For the electro-mechanical response, composites containing carbon fibers of 150 mm long demonstrated a maximum value of percentage change in resistance. These results were then compared to both 350 mm and no added carbon fibers under quasi-static tensile loading.

Polymer composites subjected to cyclic loading would exhibit damage precursors, such as crazes and microcracks, during the first few load cycles. However, damage precursors are not readily detectable with existing sensing techniques, and as such current service life prediction methods depend on macroscopic damage measures. For critical airframe structures, information on macroscopic damage does not provide adequate warning time for corrective actions. This article explores the feasibility of embedding particulate magnetostrictive particles for sensing damage precursors during the early stage of fatigue damage. The sensing is based on the notion that magnetostrictive particles undergo irreversible changes in magnetization intensity when subjected to cyclic loading, and that this change can be captured with an induction coil sensor. In the sequel, Terfenol-D particles are embedded between layers of pre-preg AS4/3501-6 material system. The specimen is then subjected to fatigue loading while monitoring the change in the strength of the magnetic flux density using pickup coil. Results show that the embedded system exhibits a change in magnetic state, in tens to hundreds of millivolts of pickup coil, starting from the first few load cycles. Scanning electron microscopy and acoustic emission data were used to validate the observed results.

Background: The goal of the study is to understand the potential energy absorption benefits ofcomponents fabricated using fused deposition modeling additive manufacturing under high strain rateloading.

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Electrical and shear behaviour of electrically conductive glass fibre/epoxy composites is studied under interlaminar shear loading. A well-connected network is developed by dispersing carbon nanotubes in the matrix and reinforcing micro carbon fibres between the glass laminates. The effect of carbon fibre length and their densities on the electrical and shear behaviour of the composite is investigated. Although interlaminar shear strength was increased by 20% with addition of carbon fibres, they failed to bridge the delamination between the laminates. For all composite types, there is no change in resistance during elastic deformation due to the formation of new contacts between the CNTs. However, during the non-linear deformation, the carbon fibres debonding and micro-crack coalescence increased resistance steadily for all cases. The composites of shorter carbon fibres showed a higher slope in the resistance change and a maximum peak resistance change compared to that of longer carbon fibres.