Primary and secondary pyroelectric effects in macro-fiber composites

Materials like the Macro-fiber Composite (MFC) are employed in energy harvesting applications utilizing the piezoelectric effect. However, energy harvesting using the pyroelectric effect in MFCs is an unexplored topic. This paper takes strides in understanding the thermal micromechanical interactions that MFCs experience due to this effect and leads to a better understanding of how MFCs behave in thermal environments. In this work, the pyroelectric coefficient (primary and secondary) are estimated for P1 and P2 Macro-fiber Composites (MFCs) using micromechanical modeling and experimental techniques. The coefficient of thermal expansion (CTE) is estimated using micromechanical theory for both MFC types which is consequently used in the modeling of the pyroelectric coefficient. Secant based moduli are used to better approximate the properties of components of MFCs in the regime of linear elasticity. Two experiments are conducted to measure the pyroelectric coefficient under different boundary conditions. In the first experiment, the thermal expansion of the MFC is constrained in a Kevlar envelope, while in the second experiment, the MFC is epoxied onto a metal shim allowing restricted deformations. Thermal experiments were conducted in an altitude chamber where the resulting average pyroelectric coefficient is calculated for both experiments.