University of Massachusetts, Dartmouth,
Keywords: CNT, composites
Summary:Multi-wall carbon nanotubes (CNTs) are used to detect the damage in polymer composites under various types of mechanical loads. To detect damage in composites, electrical conductive network generated by well dispersed CNTs is used. A combination of shear mixing and ultrasonication are used to achieve good dispersion of CNTs with low percolation threshold in epoxy matrix. Rubber particulate is added to epoxy polymer to determine the effect of different damage mechanisms on electro-mechanical response. At higher weight fraction of rubber particulates, the fracture surface of composites demonstrated severe stress whitening associated with void growth around the particulates. In addition to electrical measurements, acoustic emission studies are also conducted and later compared with that of electrical response. The investigation of damage sensing capability of CNTs embedded polymers at impact loading conditions revealed that the electrical response correlates well with the damage evolution captured using high-speed images. With success of damage sensing in particulate composites, experiments are performed on natural fiber laminated composites. With additional reinforcement of short carbon fibers between the laminates, a three-dimensional conductive network is generated along with embedded CNTs in the matrix. At higher fiber densities of carbon fibers, the electrical resistivity of natural fiber composites can be reduced to 0.019 Ohms-m. Numerical studies are also explored in conjunction with theoretical model to predict the change in number of contact types of CNTs under tensile load. The analytical predictions are later compared with experimental findings.