Multifunctional carbon fiber epoxy-matrix composites for energy harvesting

This work provides a transformational technology that allows large-scale cost-effective thermal energy harvesting. The technology is enabled by continuous carbon fiber polymer-matrix lightweight structural composites that have been modified for thermoelectric abilities in the through-thickness direction. Structural composites are in contrast to exotic and structurally weak semiconductor materials of the prior art. Moreover, they enable self-powered structures. The composite modification involves minor additives introduced to the interlaminar interface by fiber prepreg surface coating using liquid-based dispersions of thermoelectric particulate fillers (tellurium and a minor amount of bismuth telluride). Except for the coating, the composites are conventionally fabricated, thus allowing large low-cost energy-harvesting multifunctional structures. The large area helps reduce the electrical resistance, hence enhancing the power output. The modified interlaminar interface region is 33 μm (or less) thick, thus amounting to 14 vol.% (or less) of the composite. The interlaminar interface modification greatly decreases the electrical resistivity, decreases the thermal conductivity, and increases the thermoelectric power, thereby increasing the dimensionless thermoelectric figure of merit ZT (70° C) from 2.8 x 10-⁷ to 0.38. The technology provides a new avenue for obtaining self-powered structures and a new source of clean energy.