Strain field measurement of filament-wound composites at ±55° using digital image correlation: An approach for unit cells employing flat specimens

Testing of filament-wound composites (FWC) with simplified methods is studied until now in order to generalize the mechanical response of FWC structures. To assure a good analogy between meso- and macro scales, it is necessary to design a representative specimen that include the characteristic winding pattern. This research aims at characterizing the strain field of FWC pattern at ±55° using flat specimens by measuring the displacement field with digital image correlation. Experimental procedure involves tensile testing of epoxy/glass specimens with two unit cells aligned at hoop and axial direction of the winding pattern. Validation of the strain values from digital image correlation is carried out by comparing them with strain gauge measurements and FEM simulations. Failure sequence and modes of FWC flat unit cells show good concordance with those observed in FWC cylinders exposed to buckling in previous works [1].