A study of the mechanical anisotropy of high‐draw, low‐draw, and voided PVDF

The mechanical anisotropy of oriented PVDF sheet is examined using a variety of experimental techniques. The mechanical behavior is similar to that observed previously for low‐density polyethylene and nylon and consistent with a parallel lamellar crystalline structure. The s 31 compliance is reduced in magnitude by drawing to higher draw ratio, but the reduction in the piezoelectric coefficient d 31 is less marked, suggesting that the piezoelectric response cannot be related solely to dimensional changes under stress. Drawing to high draw ratio increases the s 33 compliance, and this is further increased by introducing voids. The corresponding d 33 piezoelectric coefficient is not changed significantly by drawing to high draw ratio, or by the introduction of voids, again indicating that the piezoelectric behavior relates to factors other than dimensional changes.