Eco-friendly walnut shell–reinforced ABS composites fabricated by DLP 3D printing: mechanical, thermal and tribological performance

Purpose This study aims to evaluate the thermo-mechanical and tribological performance of digital light processing (DLP) printed acrylonitrile butadiene styrene (ABS) composites reinforced with walnut shell (WS) powder at 0, 1, 3 and 5 Wt.% and to determine an optimum filler loading for balanced properties. Design/methodology/approach ABS/WS slurries were prepared and DLP printed (405 nm). Density was measured via the Archimedes method; chemical and thermal behavior were examined by Fourier transform infrared spectroscopy and differential thermal analyzer; and tensile (ASTM D638), compressive (ASTM D695), flexural (ASTM D790) and pin-on-disc wear (ASTM G99) tests were conducted. Fracture morphology was assessed by scanning electron microscopy. Findings WS addition increased composite density and elevated melting temperatures (Tm1: 258→271 °C; Tm2: 278→286 °C) while slightly reducing Tg (118→108 °C). Tensile strength decreased with loading (45.01→28.62 MPa at 5 Wt.%); compressive and flexural strengths peaked at 1 Wt.% (54.71 and 106.41 MPa) and declined thereafter. In contrast, the tribological performance improved significantly with increasing WS content, as the coefficient of friction (COF) decreased from 0.34 for neat ABS to 0.073 for the 5 Wt.% WS composite, corresponding to an approximately 78% reduction and indicating enhanced wear resistance. Research limitations/implications This study was limited to four WS loadings and room-temperature testing conditions. Impact behavior, long-term durability, humidity/temperature cycling, worn-track morphology and scale-up rheology were not investigated. In addition, detailed particle size distribution and quantitative dispersion analyses of WS powder were not performed. Future studies should address these aspects to further validate the performance and industrial applicability of DLP-printed ABS/WS composites. Practical implications WS-reinforced ABS-like composites show potential for low- to moderate-load DLP-printed functional parts where reduced friction and improved wear resistance are required. Based on the applied loads of 10–20 N, possible applications include sliding guides, polymer bushings, low-friction support elements, cable carriers, fixture parts and small housings used in automotive interior systems, household appliances, lightweight mechanical assemblies and customized additive-manufactured components. While 1 Wt.% WS offers a balanced mechanical response; higher WS contents may be preferred when friction reduction is the main design requirement. Social implications Using an agricultural by-product (WS) supports circular economy goals by valorizing waste and reducing reliance on purely petrochemical fillers. Originality/value This study reports the use of WS powder as a sustainable lignocellulosic bio-filler in a DLP-processed UV-curable ABS-like resin system, extending WS reinforcement beyond conventional polypropylene and epoxy matrices. The work provides new composition–property insights into DLP-printable ABS/WS composites and highlights a pronounced tribological improvement, with the COF decreasing from 0.34 for neat ABS to 0.073 at 5 Wt.% WS. This demonstrates the potential of WS addition for eco-efficient, low-friction additive-manufactured components.