Experimental Study on the Determination of Test Conditions for the Simulated Human Body Environment of Biodegradable Hybrid Composite Bone Plates

ABSTRACT This study experimentally investigates the fatigue behavior of a hybrid bone plate made of a carbon fiber (CF)/nylon non‐degradable biocompatible composite and a phytic acid coated magnesium (Mg) wire/polylactic acid (PLA) biodegradable composite. Hybrid structures are fabricated using successive 3D printing and thermoforming techniques. To evaluate the effect of stress in the hybrid bone plate on the fatigue behavior under wet conditions, an eccentric compression fatigue test of a simple beam‐type sandwich specimen with the same composite as the hybrid bone plate is conducted by considering the human gait. In the beam‐type hybrid specimen, no significant damage or cracking is observed after 200,000 cycles under wet and dry conditions. However, moisture deteriorates the structural integrity of the hybrid bone plate when a repetitive load of 30–70 N is applied, showing a 50% higher amplitude than that of the dry condition; after 60,000 cycles, noticeable cracks and corresponding unstable fatigue behavior are observed. This is attributed to the imperfect bonding between the two composites and the fastening condition of the screws, which should be considered in the fabrication of specimens and fatigue tests for the human body environment.