In-situ characterization of 3D printed continuous fiber reinforced composites: A methodological study using fiber Bragg grating sensors

Abstract This work demonstrates the applicability of optical fiber Bragg grating (FBG) sensors for in-situ characterization of continuous fiber reinforced thermoplastic composites (CFRTPCs) fabricated through the Fused Deposition Modeling (FDM) technique. Prismatic carbon and glass fiber reinforced Nylon composite specimens were built with various fiber orientations using a MarkTwo desktop 3D printer. FBGs were embedded along with thermocouples (TCs) into the middle-plane of the composite structures for simultaneous monitoring of both residual strains and temperature profiles developed during the building procedure. Additionally, the residual strain magnitudes were further investigated at a post-fabrication state. The samples were then subjected to thermal loading for measuring the thermally induced strains as a function of applied temperature and consequently, the composites' coefficients of thermal expansion (CTEs), based on the recorded FBG wavelengths. The results indicate that the in-process generated temperature profiles and the calculated CTE values are vigorously affected by the fiber type and orientation. It is also shown that the developed strain fields are strongly dependent on the fabrication induced temperature profiles as well as the composites' expansion behavior under applied temperature.