Abstract:

By describing the damage zone of the impacted laminate as a soft elliptical inclusion of the material, the elastic modulus is determined by the dent depth on the impact face. By using the hybrid stress finite elements with an arbitrary elliptical inclusion for anisotropic plates to model the damage zone, the bar elements to model the stringers, the nail elements to model the rivets (or adhesives) and eight node equal parametric elements to model other regions, an analytical method is established for the stress and strain distribution of impact damaged stiffened laminates. The point stress criterion, maximal stress criterion and maximal shear stress criterion are used to determine whether or not the skin, the stringers, and the rivets (or adhesives) are compressed to fail. A good agreement between the predicted residual strengths and experiment results is obtained. The effects of some factors on residual strength are considered, such as damage size, damage shape, lay-ups, etc.

Key words: composites, impact damage, residual strength, elastic inclusion, stiffened laminate