Abstract
Additively manufactured Polylactic Acid (PLA) and Carbon Fiber Reinforced Polylactic Acid (PLA/CF) composites are promising materials for use in applications involving moisture environments. Carbon fiber (CF) is known to enhance the mechanical properties of PLA composites. However, recent studies suggest that the addition of CF may not consistently improve mechanical performance under moisture exposure. Moreover, most existing studies on moisture absorption use specimens with 100% infill density, whereas practical applications often require reduced material usage to enhance performance under loads with reduced weight, necessitating infill densities lower than 100%. One of the critical aspects of additive manufacturing is the integration of topology optimization in products, which often involves using less than 100% infill density to achieve optimized designs. This study aims to fill the gap in the literature by providing valuable insights into the effects of moisture absorption on PLA and PLA/CF composites with less than 100% infill density. This study aims to conduct a comparative analysis between PLA and PLA/CF in moisture environments by immersing samples in distilled water and sea water for a period of five weeks. Results indicate that PLA/CF composites exhibit higher moisture absorption rates and more significant dimensional changes compared to pure PLA, particularly when exposed to sea water. Mechanical testing, including tensile, flexural, and inter-laminar shear strength (ILSS) tests, as well as vibration tests, reveals that both materials experience strength degradation due to water absorption, with PLA/CF showing more pronounced reductions, especially in sea water conditions.