Characterization of Mechanical and Electromechanical Properties of Aluminum-Coated Poled Orthotropic PVDF Film

This study provides a comprehensive mechanical and electromechanical characterization of aluminum-coated, poled polyvinylidene fluoride (PVDF) films—materials widely used in sensing, actuation, and energy-harvesting applications. The authors investigated orthotropic tensile properties using ASTM D638 dog-bone specimens, quantifying directional stiffness variations from 3.82 GPa in the machine direction to 1.64 GPa in the transverse direction (page 6; Fig. 4). Failure modes and strain distributions were visualized through full-field 3D digital image correlation and optical microscopy (page 9; Fig. 8), revealing strong dependence on loading orientation due to molecular alignment produced during poling. Electromechanical testing quantified piezoelectric strain coefficients d31, d32, and d36 using three complementary methods—DIC direct strain, DIC displacement, and mechanical pull testing—showing d31 ≈ 24.4 pC/N, d32 ≈ 3.3 pC/N, and negligible shear contribution (d36 ≈ 0). The results validate analytical orthotropic formulations for predicting off-axis stiffness and demonstrate the material’s strong mechanical flexibility relative to ceramic piezoelectrics, enabling its use in advanced metamaterial and biomedical device applications.