Recycled Carbonyl Iron-Biodegradable PLA Auxetic Composites: Investigating Mechanical Properties of 3D-Printed Parts Under Quasi-Static Loading

Auxetic structures showcase notable properties such as high indentation resistance, shear stiffness, fracture toughness, and acoustic energy absorption. Recent advancements in additive manufacturing have facilitated the creation of complex auxetic designs, but there has been less emphasis on developing new materials. This study focuses on using recycled iron powders mixed with biodegradable polymers by using the solution casting method to create sustainable, 3D-printable materials for energy absorption applications. This research involved examining a 2D re-entrant structure, evaluating the effects of varying iron powder concentrations in the polymer. The analyses included thermogravimetric analyses, differential scanning calorimetry, and microstructural examination, alongside compression tests to assess strength and absorption capabilities. The most effective 3D-printed composite, containing 10% iron powders, demonstrated a substantial improvement in specific energy absorption (SEA of 2.051 kJ/kg compared to neat PLA with an SEA of 0.160 kJ/kg) and exhibited favorable mechanical and thermal properties. The TGA showed that adding iron powder reduced PLA’s onset degradation temperature from 340 °C to 310 °C, 295 °C, and 270 °C for 5%, 10%, and 15% iron, respectively, confirming iron’s catalytic effect on PLA degradation. The DSC analysis showed that adding iron powder increased the degree of crystallinity from 5.63% for pure PLA to 5.77%, 6.79%, and 6.91% for 5%, 10%, and 15% iron, respectively, indicating iron’s role as a nucleation agent. These results highlight the potential of novel iron/PLA 2D re-entrant composites for energy-absorbent applications, emphasizing sustainability and cost-effectiveness.