On edge crack torsion test method to measure mode III interlaminar fracture toughness of composite laminates

摘要

An experimental method to measure Mode III interlaminar fracture toughness of composite laminates is proposed. When a rectangular strip bar specimen with uniform embedded delamination is twisted (Edge Crack Torsion specimen), the stress field at the crack tip area becomes mode III as proved through a superposition technique. An accurate expression of the energy release rate is also derived. The theoretical results are compared with finite element solutions and found to be fairly accurate over a wide range of ratios between the specimen thickness and the delamination width. From the finite element solution, necessary end conditions and the effect of the existence of the ends on the distribution of energy release rate are discussed. The disturbance is only limited in the neighborbood of the supported edges with the energy release rate being smaller compared to within the area of uniform distribution.