Development of functional gradient multi-material composites using Poly Lactic Acid and walnut shell reinforced Poly Lactic Acid filaments by fused filament fabrication technology

In construction and architectural industries, multi-material additive manufacturing is gaining more interest because of obtaining the combined material properties in a single additive process by multiple materials. The present work concentrates on developing functionally gradient multimaterial composite using Poly Lactic Acid (PLA), and novel extruded walnut shell particle reinforced Poly Lactic Acid (WPLA) by Fused Filament Fabrication technology. This work followed single and multi-gradient material deposition approaches, and their mechanical, thermal, and tribological properties were compared with standard 3D printed PLA and walnut shell-reinforced PLA composite. Among the 3D printed functional graded multi-materials, the composites with single-gradient PW configuration exhibits better compressive and D shore hardness value of 63.68 MPa and 76.2 compared with the neat PLA composite. The results show that considering the tensile and flexural samples the single gradient PLA samples shows better values when compared with all other multi gradient prepared composites. The highest heat deflection temperature of 56 C was observed on the WPLA composite and for gradient materials PW composite which is PLA (50%) and walnut shell reinforced PLA (50%) sample exhibits the maximum heat deflection temperature of 54.4 C. Furthermore, considering the tribological and thermal properties, the multi-gradient composite of WPW configured with PLA of 40% as inner core exhibits the lowest thermal conductivity of 0.087 W/mK and a specific wear rate of 1.631 x 10(-6) mm(3)/ Nm when compared with neat PLA composite. Therefore, among the novel functional graded multi-material, the sample PW with PLA (50%) and walnut shell reinforced PLA (50%) composite will be more suitable for semi-structural applications, and the composite with WPW designation (PLA of 40% as inner core) will suit the high wear-resistant and constructional building panel material for thermal proofing applications.

Automated summary

In this study, functionally gradient multimaterial composites were developed using PLA and WPLA. The single-gradient PW composite exhibited better compressive performance and hardness values, suitable for semi-structural applications. The WPW composite with PLA as the inner core showed superior thermal conductivity and wear resistance, making it a suitable material for high-wear and thermal proofing applications.