Optimal strain gage location for determination of mode I stress intensity factor for orthotropic laminates using a single strain gage

The present work discusses a robust method developed for determination of mode I stress intensity factor (KI) of orthotropic laminates using a single strain gage and based on a three parameter strain series representation ahead of the crack tip. Appropriate radial location of the strain gage ahead of the crack tip is important in the sense that strain gages placed either very near or very far from the crack tip might lead to inaccuracies in the estimated SIFs due to 3D effects near the crack tip or inaccurate strain field representation at farther distances. The theoretical formulation has been presented for determination of angular location, orientation and the upper bound on the radial location (rmax) for pasting the strain gage which could be subsequently used for accurate determination of KI. Numerical simulations have been presented considering edge cracked [902/0]10S carbon-epoxy orthotropic laminates to illustrate the determination of rmax and KI of such laminates.