ESPI measurements of strain on a CFRP-reinforced bending beam

This paper presents 3D electronic speckle pattern interferometry (ESPI) measurement results of strain components at the end of a carbon-fibre reinforced polymer (CFRP) plate adhesively bonded to a reinforced concrete beam. To minimise speckle decorrelation because of the inevitable rigid-body motion of the measured specimen,the load was increased in small increments. Two evaluation schemes are compared: the step-by-step addition of the measured displacement components and regain of the correlation by image shifting. Strain is evaluated by interpolating the in-plane displacement measurements along selected lines, and is compared with results from finite element analysis (FEA). An uncertainty estimate is given.