Determination of KI in orthotropic laminates with double ended cracks using a single strain gage technique

Abstract

Experimental determination of mode I stress intensity factor (SIF) KI in orthotropic composites is of significant importance. In this direction, single strain gage techniques that are developed for measurement of KI are based on the solutions of the single ended crack theories and those have also been tested only for single ended cracked orthotropic configurations. Although, certain limitations prevent straight forward application of these single ended crack solutions to the double ended configurations, the present investigation aims at demonstrating the use of such a single strain gage technique recently proposed by the authors to the configurations containing double ended cracks or internal cracks in orthotropic materials for the accurate measurement of KI. Importantly, the present investigation also proposes existence and determination of optimal strain gage locations in double ended cracked orthotropic plates for the accurate measurement of KI. Studies have also been carried out to understand the effect of change in geometry of the configuration on the optimal gage locations. The results of the present investigation have been observed to substantiate the theoretical formulations in terms of accurate determination of KI. Numerical results clearly show that the proposed single strain gage technique yields accurate values of KI when the gage is placed at an optimal gage location. On the contrary, highly erroneous values of KI are obtained when the gage is placed at non-optimal locations.