Measurement of in-plane and out-of-plane elastic properties of woven fabric composites using digital image correlation

The digital image correlation (DIC) technique is employed to measure the strain fields and the five independent elastic material constants of a glass/vinyl ester plain weave laminated composite. Transverse (through-thickness) tensile and Iosipescu shear properties were measured using thick (∼19 mm) laminates, and the strain fields were compared against those predicted by a homogenized linear elastic finite element analysis. DIC reveals that the strain fields of the laminates may present heterogeneous zones, which are attributed to the heterogeneous nature of the woven fabric architecture. Homogenization of the DIC strain fields to produce two-dimensional stress-strain plots yields average strains and elastic properties of the woven composite which can be similar to those measured by conventional (localized) strain gages. Important differences were found for the transverse tensile and Iosipescu shear tests, where differences of 26.4%, 28.6% and 11.9% were obtained for the measured transverse elastic modulus (Ez), in-plane shear modulus (Gxy) and transverse shear modulus (Gxz), respectively.