Luminous behavior and tensile property of twisted side-emitting polymer optical fibers bundles

Side-emitting polymer optical fibers (SEPOFs) are known for providing a strong bright luminosity and have been applied in textile industry. Commonly, available SEPOFs with diameters of 2–3 mm provides higher luminous intensity when combined with textiles, while higher bending stiffness increases difficulty for incorporation with textiles. The SEPOFs with smaller diameters are characterized as more flexible and more suitable for textiles, while their poor mechanical properties limit final applications. The twisting can keep the structure bundles of SEPOFs stable. In this work, SEPOFs with diameter of 0.25 mm were used and different numbers (15, 20, and 25) of SEPOFs were assembled into one bundle by applying different twists (10T/m, 20T/m, and 30T/m). The twisting structure, tensile behavior and side-illumination property of the twisted SEPOFs bundles were investigated. As a result, the stable structure of the twisted SEPOFs bundles was found, and the twisting angles increased with higher twisting degree. The yield strength and strain of twisted SEPOF bundles were about 80–84 MPa and 10–12%, respectively. The initial modulus tended to decrease with a higher twisting degree, but it was still higher than 1.2 GPa. The break of the twisted SEPOFs bundles followed the ‘optimal twist’ theory, which suggested optimal twisting degree for different samples. Besides, the attenuation of side illumination intensity of twisted SEPOFs bundles was found, and the twisting structure had a complicated influence on the side illumination intensity. We suggest that this work will help to promote the use of SEPOF-based bundles and extend to textile applications.