Comparison of Different Techniques for Strain Monitoring of a Biaxially Loaded Cruciform Specimen

:  This study focuses on the evaluation of several strain measuring techniques for the instrumentation of an in-plane biaxial test bench. Strain gages, electronic speckle pattern interferometry (ESPI) and digital image correlation (DIC) were used combined or separately to measure the strains in the central gauge area of a biaxially loaded cruciform composite specimen. Applicability of the technique for this specific test and accuracy of the results are important parameters in the evaluation process of the different strain measuring techniques. The results of the three techniques are compared with the results obtained with a 3D finite element (FE) model. It is shown that DIC is the most promising technique because of its full-field character and ability to cope with vibrations of the test bench. The main drawback remains its incapability to correlate across discontinuities.