Optical sensor-based measurements of thermal expansion coefficient in additive manufacturing

The applicability of fiber optic sensors for measuring the coefficient of thermal expansion (CTE) of thermoplastic parts fabricated through Additive Manufacturing is investigated. Prismatic specimens were fabricated via the Fused Deposition Modeling (FDM) technique and Fiber Bragg Grating (FBG) sensors were embedded within the structures during the building process. The specimens were manufactured featuring various raster orientations and were then subjected to thermal cycling. The wavelength measurements recorded from the optical sensors were employed for the calculation of the thermally induced strains in the specimens as a function of temperature. The obtained curves presented a linear behavior until the Tg, where the internal phase change is manifested with a peak and a subsequent decline of the curve. The CTE was calculated and the effect of raster orientation on the thermal expansion behavior was identified.