Effect of Layer-Height on Tensile Stress-Distribution and Crack-Width and Propagation in 3D Printed Fiber-Reinforced Flexural Elements (2021-12)¶

This paper evaluates the effect of layer height on the flexural response and crack propagation behavior of 3D-printed steel fiber-reinforced mortar beams. Beams printed with three different layer heights (5, 10, and 15 mm), with other dimensional and printing parameters maintained the same, were tested in four-point bending. The flexural strength increased with layer height in the range explored. Fiber lengths larger than the layer height introduced enhanced interlayer defects. Flexural load-deflection data were employed to determine a constitutive tensile stress-strain relationship. Digital image correlation (DIC) was used to measure the crack width along the depth, along with the strain profile. The relationships between stress and crack width were developed as a function of distance from the neutral axis, which demonstrated higher residual stress at a given crack width for the specimens with higher layer height. The study shows that a small amount of fibers in 3D-printed mixtures ensures better mechanical properties and that higher layer heights (within the limits used here) are beneficial in terms of mechanical behavior and speed of construction.