Effect of Shot Peening on the Fatigue Life of Polylactic Acid Parts in Automobiles

Polylactic Acid (PLA), is a biodegradable thermoplastic and most widely used materials in automobiles also inherent fatigue performance limitations and its deployment in demanding load-bearing automobile applications. Shot peening, a well-established surface treatment known to significantly enhance the fatigue life of metallic materials, presents a potential post-processing strategy to improve the durability of polymers. The proposed work investigation into the effects of controlled shot peening pressure on the various behavior of injection molded PLA specimens. The outlined methodology encompasses the fabrication of PLA samples conforming to ASTM standards, the application of shot peening using precisely defined parameters, comprehensive characterization of the resulting surface modifications (including roughness, hardness, morphology, and systematic uniaxial fatigue testing according to ASTM D7791. Fatigue tests will generate fatigue behavior and fatigue life (by varying number of cycles) for both as-built and shot-peened samples, allowing for quantitative comparison. This study are to quantify the changes in fatigue life and endurance limit attributable to shot peening, to correlate these performance alterations with the measured surface characteristics (fractography), and to elucidate the governing mechanisms, specifically evaluating the interplay between potential benefits like compressive stress induction and detrimental effects like surface damage. Surface roughness of 2.9 Ra, 78 shore D-hardness and fatigue strength and life increases, reaching a peak of 34,000 cycles at 47 MPa @ 4 bar shot peened pressure. Utilizing shot peening for printed PLA materials for enhancement and the identification of potentially responses as a right choice. This research addresses a critical knowledge gap concerning the applicability and effects of shot peening on injection molded-produced polymers, potentially enabling the broader use of PLA in structural roles.