2017 年 17 巻 1 号 p. 15-20
A strain distribution of a carbon fiber reinforced plastics (CFRP) laminate plate due to a light load is measured by electronic speckle pattern interferometry (ESPI) for evaluating the stiffness degradation of the CFRP plate. The stiffness of the CFRP plate is decreased by applying the load of 62.5 % for the fracture load using a three-point bending test. Strain distributions due to the load less than 12.5 % for the fracture load using the same bending test are measured by ESPI before and after the damage. Strain distributions less than 2.5 × 10-4 are obtained and indicate strain increasing after the damage. The strain increasing ratio due to the stiffness loss is larger than the stiffness loss ratio obtained from the relationship between the load and the displacement. Additionally, the distribution of strain increasing ratio is evaluated and shows the variation less than 10 % immune to the surface structure of the laminate. Therefore, the evaluation of the stiffness degradation of the CFRP laminate by ESPI is effective, and can realize a non-destructive evaluation.
