Method for testing residual strain of composite material winding pipe based on grating sensor

The invention provides a method for testing residual strain of a composite material winding pipe based on a grating sensor. The method comprises the following steps: providing a core mold; spirally winding a plurality of layers of composite fiber materials on the core mold; after winding to the middle layer of the preset number of layers, enabling a main shaft to stops rotating, fixing four grating optical fibers to the outer wall of the top of a winding layer, and locating grating areas of the four grating optical fibers on the four edges of a parallelogram respectively; conducting winding operation of remaining layers; performing heating and curing after winding is finished, recording initial wavelength values of four gratings after the curing process is finished, then cooling to a preset temperature, and recording wavelength values of the four gratings at a cooling end point; and respectively calculating the axial residual strain value and the circumferential residual strain value of the composite material