2.3. Static Tests

The three-point bending tests were performed on Autograph AG-X plus (Shimadzu, Tokyo, Japan) equipped with a force sensor with a measuring range up to 1 kN (1.0 class). The crosshead speed was set to v_c = 1 mm/min. The values of Young’s modulus were determined from the linear range of the stress-strain curve (for deformations of 0.0005–0.0025). For each infill, seven measurements were taken. The mean and standard deviation for Young’s modulus, flexural stress, and strain were determined.

The density of PLA was determined using a hydrostatic method with distilled water at 23 °C as the immersion liquid. The measurements were carried out with Radwag AS160 C2 (Radom, Poland) laboratory balance cooperating with the kit for determining solids’ density.