Direct measurement of residual strains in CFRP-tungsten hybrids using embedded strain gauges

In this work, the implementation of fully embedded electrical resistance strain gauges was studied for a hybrid material system. The samples were laminated using carbon-fiber-reinforced plastic (CFRP) and tungsten. The raw materials and the adhesive used for bonding strain sensors were characterized to understand the overlapping sources of non-linearity and error. Test-specific correction functions for a thermal output were determined for the strain gauge measurement and comparative fiber Bragg grating (FBG) measurement. The strain accumulation in the fiber direction during the cool-down phase for different cure cycles was analyzed using a finite element simulation. According to the results, embedded electrical resistance strain gauges can be used to determine the thermal expansion of a hybrid laminate with acceptable accuracy when thermal output is compensated for using case-specific correction functions accounting for measurement setup, the stiffness of the gauge bonding adhesive, and embedding.