Abstract: This invention comprises the use of diacetylene-containing polymers, e.g., olyamides containing reactive diacetylene groups that change their absorption in the visible spectrum with the application of strain as a strain sensing device in various organic matrix composites such as an epoxy laminated composite. The built in sensors in accordance with this invention will not affect the mechanical performance of the composite and will indicate strain without the need for extensive electronic equipment to measure the light pulse amplitude or phase before and after strain.