Glass fiber cross-ply composites with electrophoretically deposited carbon nanotubes for sensing of transverse cracking
Date
2020
Authors
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Publisher
University of Delaware
Abstract
Multi-walled carbon nanotubes can be implemented in hierarchical composites to improve their electrical and mechanical properties and enable opportunities for in situ sensing of damage and applications in structural health monitoring. The multi-walled carbon nanotubes are sonicated in an aqueous solution with ozone before functionalizing with polyethyleneimine. These functionalized carbon nanotubes can be deposited onto electrically insulated substrates to create a piezoresistive network. ☐ The piezoresistive network is able to identify damage formation. As a load is applied to the network, the contact points will be pulled further away, creating an increase in the resistance. When permanent damage occurs, like fiber breakage, the resistance will experience a permanent increase in resistance due to the inability to form the network in that direction. ☐ The sensing capabilities of these carbon nanotube sensors are able to identify the three types of damage: elastic region with minimal damage formation, transverse cracks forming, and delamination occurring. This new technology was validated using an acoustic emissions sensor and edge replication. The sensing network can also recognize what stage of damage is occurring. All damage begins by reopening previous cracks before accumulating additional damage. The final stage involves generating new damage. The piezoresistive network was able to identify these different stages as verified with acoustic emissions. ☐ The edge replication further shows the ability of these carbon nanotube sensors to suppress crack propagation until higher strains are achieved. The nanotubes ease the harsh fiber-matrix interphase, mitigating the stress concentrations. This will allow for the load transfer to be slowly increased. As a result, higher strains are required to saturate the samples. ☐ The carbon nanotube sensors can provide both electrical and mechanical benefits without compromising the properties of the E-glass cross-ply laminates. Direct applications of this technology include structural health monitoring. The sensors will be able to detect damage to the infrastructure without requiring extensive monitoring equipment. It will also be able to suppress damage accumulation from occurring until higher strains are achieved. These sensors are low maintenance while still providing immediate feedback regarding damage accumulation. ☐ The carbon nanotube coated E-glass fabric can be used to manufacture a cross-ply laminate that is able to sense damage as it occurs. These sensors can recognize all stages of crack formation prior to failure. The electrical improvements, paired with mechanical improvements, make this technology unique for structural health monitoring applications.
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Keywords
Composites, Multi-walled carbon nanotubes, Piezoresistive network