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Degradation of Carbon Fiber Composite Materials Due to Electrical Current and Potential Impact on Synergistic Durability



Composites materials are often subjected to multi-physical conditions in different applications where in addition to mechanical load, they also need to sustain other types of loads such as electrical currents. Hence durability and damage tolerance of composite materials for both mechanical and electrical loads need to be studied. Although the durability of composite materials under mechanical loading has been studied over several decades, their response to electrical currents is still not fully understood. Damage tolerance for mechanical response may or may not be sufficient for a desired durability in electrical response. Electrical effects are often coupled with structural integrity and thermal behavior. This inherently multi-physical behavior needs to be understood and analyzed to facilitate new multi-functional material design. An essential first step towards that goal is to understand how multi-physics properties depend on local micro-structural details. In this study, anisotropic electrical behavior is measured experimentally and threshold of nonlinear behavior has been quantified. This directly relates electrical response with microstructural changes. The thermal response is also studied with thermography tests and the temperature distributions were compared to those of the electrical measurements to facilitate identification of potential damage locations. A 3D X-ray microscope has been used to visualize and quantify (down to 1 micron) such local material state changes due to electrical current. This ongoing work is expected to form a foundation for future multifunctional material development.

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