Effect of beech wood particle content on the printability and mechanical performance of photopolymer composites manufactured by stereolithography

The incorporation of lignocellulosic fillers into photopolymer matrices offers a promising route toward more sustainable additive manufacturing materials. However, their influence on stereolithography (SLA) processing and mechanical performance remains insufficiently understood. This study investigated the printability limits and mechanical behavior of beech wood (Fagus orientalis L.) particle – reinforced photopolymer composites produced via SLA. Beech wood particles were incorporated into an acrylate-based resin at 0%, 5%, 10%, and 15% by weight. Increasing wood content altered resin optical and rheological characteristics, resulting in UV light attenuation, reduced cure depth, and impaired interlayer adhesion. To compensate for these effects, bottom exposure times were increased from 40 s for the neat resin to 60 s and 70 s for the 5% and 10% formulations, respectively. Although specimens containing 15% wood particles could be fabricated, defects such as incomplete curing and delamination prevented mechanical testing. Tensile and compressive properties decreased systematically with increasing wood content due to weak interfacial bonding between hydrophilic wood particles and the hydrophobic photopolymer matrix, as well as microstructural heterogeneities. Among the investigated formulations, the composite containing 5% beech wood particles exhibited the most favorable balance between printability and mechanical performance. These results define filler-content thresholds for wood-filled SLA composites.