Investigation of Mechanical Behavior of Nano-alumina-Reinforced Polylactic Acid Composite Through Micro-mechanism Approach

The study focuses on evaluating the mechanical behavior of polylactic acid (PLA) composites infused with varying weight percentages of nano-alumina (ranging from 0 to 15%) through mechanical tests, such as tensile, compression, bending, impact, and fatigue. Further, the underlying micro-mechanisms, post-mechanical testing, are also investigated through ex situ characterization. The tensile and bending strengths were found to be relatively lower in the PLA composites, while the compressive strength increased with the addition of alumina, owing to the crack opening and closure phenomena, respectively. The impact and fatigue samples displayed a transitional variation in strength and number of loading cycles up to failure, respectively, at 10% by wt. of alumina. The above phenomena can be attributed to the crack deflection mechanisms (such as crack deviation, bifurcation, and bowing), which reduce the crack propagation rate up to 10% by wt. of alumina inclusion. However, with further addition of alumina, the crack nucleation phenomenon increased, leading to a decrease in the number of loading cycles to failure. In addition, the findings have important implications in designing and developing advanced composites that can be employed as lighter structural parts in the aerospace, automobile, medical, and defense sectors.