Strain transfer of fiber Bragg grating sensors in fiber-reinforced polymer composites with different fiber orientations and temperatures

A comprehensive investigation integrating a newly developed strain transfer model and corresponding experiments has been performed, so as to characterize and quantify the fiber Bragg grating (FBG) sensor's strain transfer mechanisms and measurement accuracy in composite structures considering fiber orientations and temperatures. Tensile tests at different temperatures (20 ℃, 40 ℃, 80 ℃, and 100 ℃) were performed on the related specimens. The results show that the geometry and temperatures affect the measurement accuracy significantly, and with the strain modification based on the developed model, the accuracy has been substantially improved. The maximum error decreases from 9.3 % to 1.4 % at room temperature and is about 4.1 % at high temperatures. The sensitivity analysis illustrates that the embedding length is the most critical factor affecting the accuracy, followed by the polymer's shear modulus and the coating layer radius. The strain transfer efficiency has a minor sensitivity to temperature and interface parameters.