Design of a composite sub-structural beam specimen for investigating tunneling cracks under cyclic loading

The design of a thin-walled composite beam is presented whose purpose is to facilitate the study of intra-laminar tunneling cracks at the sub-structural length-scale. The beam utilizes a variable thickness reinforcement in the longitudinal direction to develop a gauge zone of near-uniform strains when loaded in a cantilever beam configuration. The beam is manufactured from E-glass fibers and epoxy resin and is tested under static and cyclic multi-axial loading. The results presented include experimental strain measurements at the gauge zone, which agree with numerical strain predictions, and observations of the developed tunneling cracks.