Split-disk test with 3D Digital Image Correlation strain measurement for filament wound composites

Abstract

The paper investigates the split-disk test methodology for measuring mechanical properties of a filament wound composite. Hoop strain is measured by three-dimensional (3D) Digital Image Correlation (DIC) on the outer surface of ring specimens. A finite element model (FEM) is employed to investigate the strain distribution along the circumference and the thickness of the ring and the effect of friction between the ring and the disk. The FE simulation shows that the effect of friction between the ring and the disk is significant, but precise quantification is difficult because of irregularities of the ring/disk contact. Both DIC strain map and FE simulation show a low strain area at the level of the split, caused by local bending of the ring. In conclusion of this work, the authors recommend: (1) to measure the strain, which is used in the stiffness calculation in the area with a 10° offset from the disk split, where the influence of the local bending becomes insignificant, (2) to use 3D DIC for precise hoop strain measurement, (2) to use concurrent FEM to estimate errors related to the difference between the surface strains and the average strains over the entire ring thickness.