Degradation Behavior and Service Life Prediction of Three‐Dimensional ( <scp>3D</scp> )‐Printed Polylactic Acid ( <scp>PLA</scp> )‐Based Composites Under Ultraviolet ( <scp>UV</scp> ) Aging

ABSTRACT Under the “dual carbon” strategy and the growing demand for automotive lightweighting, the mechanical properties and service life evaluation of three‐dimensional (3D) printed green composites have attracted considerable attention. In this study, two composite materials, rice husk (RH)/polylactic acid (PLA) and starch (ST)/RH/PLA, were fabricated by fused deposition modeling (FDM) and subjected to accelerated ultraviolet (UV) aging tests. The evolution of their microstructure, thermal stability, crystallization characteristics, and mechanical properties was systematically analyzed. The results showed that the incorporation of RH retarded the UV degradation of the PLA matrix and effectively improved its thermal stability. After 16 weeks of UV aging, the compressive strength loss rate of RH/PLA was 37.66%, while that of ST/RH/PLA reached 41.81%, indicating a more pronounced decline in mechanical properties with the addition of ST. Based on the degradation behavior of the compressive strength, an aging model was established. By incorporating the comprehensive acceleration factors of temperature, humidity, and UV radiation, the service life of the 3D printed RH/PLA composite in an automotive interior environment was predicted to be approximately 19.8 years, which satisfies the design service life requirement of 15 years.