Transverse strain effects on the thermal expansion measurement of composite structure using fiber Bragg grating sensors: Experimental validation

When transverse strain is much larger than the longitudinal one, conventional fiber Bragg grating measurement model presents significant errors in the longitudinal strain measurement. The present authors presented a fiber Bragg grating measurement model to consider transverse strain effects and numerically demonstrated the effectiveness of the model. This article experimentally validates the fiber Bragg grating measurement model by measuring thermal expansion of anisotropic composite specimens and an isotropic invar specimen. The longitudinal thermal expansion of the specimens is measured by using fiber Bragg grating sensors and compared with a reference measurement result using an optical interferometer. The proposed fiber Bragg grating model shows good agreement with the reference measurement for the longitudinal strain while large discrepancy (~22%) is observed according to the conventional one-dimensional fiber Bragg grating model.