Damage Tolerance and Nde of Polymeric Composites

As composites are being used as primary load bearing members, the increased understanding of damage tolerance of the material is becoming important. When load is applied to a structure containing a crack or damage, a small area ahead of the crack undergoes very high stress. These stresses cause further damage in this small zone. Initially this damage is at the microlevel: in isotropic materials the micro damage is in the form of slippage and microcracks at grain boundary; in composites the microdamage constitutes of matrix microcracks, matrix-fiber interface cracks and fiber pull out. The size of this damage zone varies depending on the material type and the damage tolerance i.e. energy absorbed by the damage zone is directly proportional to the damage zone.