Strain distribution measurement system and strain distribution measurement method that measure strain distribution based on distribution of reflectance or polarization characteristic

A strain distribution measurement method for a strain distribution measurement system including a material tester that deforms a test piece formed of a plain-woven or twill-woven fiber reinforced plastic (FRP) including carbon fibers to measure a mechanical property of a material of the test piece, and a strain distribution measuring device that measures a strain distribution of the test piece, the method comprising:

• measuring, by the strain distribution measuring device, the strain distribution of the test piece based on a distribution of at least one of a reflectance and a polarization characteristic on a main face of the test piece without applying or attaching a grid-like pattern on the main face of the test piece,
• wherein the strain distribution of the test piece is measured by performing processing, including a two-dimensional discrete Fourier transform (DFT), on a captured image of the main face of the test piece, the captured image being configured with a bright region and a dark region arranged in a checkered pattern, wherein the bright region corresponds to a warp of the test piece, and the dark region corresponds to a weft of the test piece.