Optimum design of symmetric composite patch repair to center cracked metallic sheet

摘要

Composite patch repair of cracked metallic aircraft structures has recently been accepted as one of the means of improving fatigue life and attaining better structural integrity. The effectiveness of such patches for cracked sheets can be measured as an achievable reduction in the crack tip stress intensity factor (SIF). In this paper, a study has been conducted to get an optimum design of symmetric (balanced) composite patch to a center cracked metallic sheet. It has been achieved considering the SIF at the crack tip of the sheet as constraint and the plan-form shape of patch and the thickness of patch as design variables. The results of square, circular, elliptical and rectangular patches are presented. The effectiveness of smaller pach length perpendicular to the crack compared to the full-length patch in the same direction ahs been brought out. A new configuration called skewed patch is studied. Reduction in weight of the patch due to skewed configuration has been brought out. The effectiveness of patch thickness over the patch plan-form shape in reducing SIF has been brought out.