A new single strain gage technique for the accurate determination of mode I stress intensity factor in orthotropic composite materials

•A strain gage technique for KI determination in orthotropic materials is proposed.•Need for optimal gage locations for accurate KI values is addressed.•A parameter rmax is proposed to assess the optimal gage locations.•A procedure is proposed for computation of rmax of any composite specimen.•Proposed approaches shown to be giving accurate values of KI.

The present work proposes a new single strain gage technique for the accurate determination of mode I stress intensity factor (SIF) in orthotropic composite materials. This work also aims at showing the existence of valid or optimal gage locations for the accurate determination of SIFs in orthotropic composites. Accordingly, a finite element based general approach is developed for the estimation of such optimal gage locations. Results of numerical examples show that the proposed strain gage technique can yield highly accurate value of SIF for orthotropic laminates when the gage is placed within the valid locations.