This thesis investigates the shear strain-driven energy harvesting performance of compliant piezoelectric composite material systems. A characterization study was performed to observe and quantify the piezoelectric shear coupling of two phase piezoelectric composite materials ranging from 0-3 (particulate) to 1-3 (fiber) composites. To this aim, the shear mode properties of piezoelectric composites were experimentally established by a novel impedance-based measurement technique, which was complemented with standard quasi-static measurements. Finite element simulations were performed to validate the new method. Moreover, homogenization-based finite element simulations served to numerically obtain the effective properties of the experimentally investigated material systems. Next, the energy-based performance of a compliant composite patch provided with interdigitated electrodes was assessed for shear and axial strain-driven mechanical excitation schemes. Numerical simulations by means of an adaptive finite element model were performed to determine the effect of the patches’ electrode geometry on its energy harvesting capability. In addition, two finite energy harvesting case studies were developed to investigate the effect of complex strain distributions and to suggest practical experimental validation schemes for the purely numerical approach presented in this thesis.