Robust characterization of crack propagation in 3D woven composites and evidences of size dependency

The failure of fibers inside the yarns of 3D woven carbon/epoxy composites is investigated experimentally by estimating the critical energy release rate GC, through the analysis of Compact Tension (CT) and Single Edge Notched Beam (SENB) specimens. Close attention is paid to the specimen design as well as the tracking of the crack growth. Several data analysis methods are compared in order to obtain a valid process for highly anisotropic materials such as 3D woven composites with a relatively large Representative Elementary Volume (REV). Variation of GC with the specimen size and geometry is obtained and evidences of the invalidity of the Linear Elastic Fracture Mechanics (LEFM) framework for 3D woven composites are highlighted.