We are designing and synthesizing multi-functional composite materials for a variety of applications including smart skin, multi-functional textiles, epidermal electronics all the way to transportation materials. These applications require electrically conductive materials that are very thin yet tough. We recently demonstrated a new direct approach to transform Vertically Aligned (VA)CNTs into dense, strong and tough textile sheets by designing a bio-inspired brick-and-mortar micro-architecture and achieving it by capillary-induced weaving and splicing of CNTs. In addition to high strength and electrical conductivity, the pristine CNT sheets demonstrate high specific fracture energy of 11,000 J/m2 at specific gravity of 1, thus four orders of magnitude higher than copper at the same thickness. This high energy dissipation results from the hierarchical micro- architecture which leads to effective nanoscale dissipation process zone size spanning several mm propagating ahead of a crack tip, in addition to significant crack bifurcations at the microscale. These results open new routes for designing strong materials having hierarchical nanoscale architectures.