Through-thickness tensile characterization and analysis of fiber-reinforced polymer composites using digital image correlation and finite element modeling

Digital image correlation (DIC)and finite element analysis (FEA)are used to assess the cylindrical spool-shaped ASTM D7291 and I-beam-shaped specimens for through-thickness (TT)mechanical characterization of thick (_25 mm)fiber reinforced polymer matrix composites. The composites are made of E-glass woven fabrics reinforcing a vinyl ester matrix. DIC full-field measurements and FEA showed a rather uniform strain distribution within the gage section of the ASTM D7291 specimen. However, strain concentrations are revealed at the bondlines between the end-tabs and the test specimen, in addition to strain gradients at the curved section of the specimen. DICmeasured and FEA-predicted strain fields of the I-beam specimens exhibited a region of uniform strain distribution within the gage section larger than that of the ASTM D7291 specimen. Nevertheless, high stress concentrations at the fillet (curved flange-to-web transition)regions and some amount of web bending occur in the I-beam specimen. Beyond providing the TT mechanical properties of the E-glass woven/vinyl ester composites, the current work discusses advantages and caveats of both promising specimens, providing quantifications of stress concentration factors and length of zones were strains and stresses may be considered uniform.