Notch sensitivity of carbon epoxy fabric laminates

An experimental program has been developed to assess the notch sensitivity of carbon/epoxy fabric laminates with circular holes. The effect of +/- 45 degrees layers on the notch sensitivity was evaluated by testing six differ ent lay-ups with increasing numbers of +/- 45 degrees layers, ranging from (0)(5)-(45)(5). The failure criteria proposed by Mar and Lin and the averag e-stress criterion were used to predict the notched fracture stress for eac h laminate. Laminate and material parameters were determined from experimen tal data for each laminate. For a range of laminates containing up to 60% o f layers oriented at +/- 45 degrees the material parameters were found to b e essentially independent of laminate lay-up. A new approach was proposed t o estimate the notched strength of carbon/epoxy fabric laminates based on t he assumption that failure of the 0 degrees plies governs laminate failure. With the use of the proposed approach, the laminate fracture parameter, H- c, utilized in the Mar-Lin criterion, could be accurately predicted for all tested laminates. The application of the proposed approach requires only t he fracture parameter of a 0 degrees ply. (C) 1999 Elsevier Science Ltd. Al l rights reserved.