Analytical Optimization of Coating Properties for Actuators and Sensors

An elasticity solution is presented for the problem of a continuous cylindrically shaped coated sensor/actuator embedded in a material system subjected to transverse strains. Results are presented for an AS4/epon 828 material system containing fiber optic sensors coated with dif ferent interphase materials. These data demonstrate that an optimal coating stiffness and thickness exists which minimizes the stress state in the host material. The optimal interphase corresponds to an integrated material system whose transverse stiffness values are similar to the host material. The results suggest that with the optimal interphase region, the onset of damage can successfully be delayed and may provide a material system whose transverse strength rivals that of the host material. Design curves are also presented for optimizing the interphase coating thickness and modulus for a general family of sensors and actuators.