Dynamic delamination of composites

Modified DCB and ENF specimens are used for the study of high speed dynamic delamination crack propagation in composite laminates. Specimens made of uni-directional fiber composites are tested for both mode I and mode II cases. Plate theory in conjunction with fracture mechanics approach is used in modeling mode I dynamic crack propagation. An interface approach based on ABAQUS is developed for modeling mode II dynamic crack propagation. The experimental results are used in the numerical simulations. The dynamic fracture toughness is obtained. The problem of a stationary or smoothly moving crack along the interface of an elastic anisotropic bimaterial is investigated. Crack surfaces are assumed to be in contact with either no friction or Coulomb-type friction. The near-tip singularities are found for both frictionless and frictional cases where the bimaterial assumes most general anisotropy. Emphasis is made on the asymptotic structures of the crack tip fields when the anisotropic bimaterial possesses an aligned plane of symmetry parallel to the crack surfaces, such as laminates made of fiber composites. The near-tip displacement and stress fields are derived. The corresponding energy release rates are also derived