Performance investigation of 3D printed clay soil using fiber Bragg grating technology

Additive Manufacturing (AM) techniques are under continuous investigation with interesting results published at both experimental and research levels. However, few investigations have been found focusing on the measurement study of internal mechanical performance which significantly influences the quality of printed products. In this study, several clay soil specimens with infill densities of 40%, 60%, 80%, and 100% were fabricated using AM method. Fiber Bragg grating (FBG) sensors were successfully mounted at the center of soil specimens (forming smart 3D printed clay soils) to monitor the horizontal strain distributions at different testing conditions. During AM process, lateral strain distributed at the horizontal center of all soil specimens presents linear rise as the increase of infill density from 40 to 100%. The strain values measured by FBG sensors are within a range between 22 and 210 mu epsilon. In soil drying process, all strain values from FBG sensors present nonlinear decrease against time with a relatively stable residual level obtained at certain time after AM. The increase of infill density from 40 to 100% leads to a corresponding shrinkage strain up to a range from - 800 to 1400 mu epsilon. In uniaxial loading tests, measured strains from FBG sensors present initial quick rise approaching two peak wavelength values. All measured strains at the center of soil specimens increase linearly as the increase of infill density values. Peak lateral strain almost doubled as the infill density increases from 40 to 100%. In this study, FBG sensor offers an effective monitoring method to investigate mechanical behavior of printed soils.