Basalt fibers (BFs) are environmentally friendly materials characterized by high strength and good wear resistance, and thus are popular candidates for reinforcing polymers. Herein, polyamide 6 (PA 6), BFs, and the styrene–ethylene–butylene–styrene (SEBS) copolymer were melt compounded sequentially to prepare fiber-reinforced PA 6-based composites. The results showed improved mechanical and tribological performances via the incorporation of BFs and SEBS into PA 6. Compared to neat PA 6, an average 83% increase in notched impact strength was achieved for the PA 6/SEBS/BF composites, which is mainly due to the good miscibility between SEBS and PA 6. The tensile strength of the composites, however, was only increased moderately, since the weak interfacial adhesion was not sufficiently efficient to transfer the load from the PA 6 matrix to the BFs. Interestingly, the wear rates of both the PA 6/SEBS blend and the PA 6/SEBS/BF composites were obviously lower than those of the neat PA 6. The PA 6/SEBS/BF composite with 10 wt.% of the BFs exhibited the lowest wear rate of 2.7 × 10⁻⁵ mm³/N·m, which was decreased by 95% compared to that of the neat PA 6. The facilitation of forming tribo-film with SEBS and the naturally good wear resistance of the BFs were responsible for the largely decreased wear rate. Moreover, the incorporation of SEBS and BFs into the PA 6 matrix transformed the wear mechanism from adhesive wear to abrasive wear.

The increasing need for lightweight, personalized, and sustainable orthopedic braces has motivated the development of bamboo fiber (BF)-reinforced polylactic acid (PLA) composites. In this study, BF/PLA composites were prepared by melt blending. The effects of polybutylene adipate terephthalate (PBAT) toughener, BF content, and a silane coupling agent on the mechanical properties were evaluated, along with their suitability for 3D printing foot braces. The results showed that at a PLA/PBAT mass ratio of 85/15 and a bamboo fiber content of 10 wt.%, the impact strength of the composite reached 7.7 kJ/m². Silane treatment of BF further improved the impact strength, with a maximum value of 11.3 kJ/m² achieved at a silane/BF mass ratio of 2/98. The optimized composite exhibited good printability across nozzle temperatures of 190–210 °C. Printing speed significantly influenced the process; a speed of 35 mm/s enabled successful fabrication of the foot brace, whereas higher or lower speeds led to model collapse due to overheating or cracking caused by insufficient interlayer adhesion. This study successfully developed a bamboo fiber-reinforced PLA composite suitable for 3D printing of orthopedic braces and identified the optimal 3D printing process parameters.

This study investigates the influence of surface-modified carbon fibers (CFs) on the structural and mechanical properties of acrylonitrile-butadiene-styrene (ABS)-based composites. A comprehensive approach employing Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurement, and thermogravimetric analysis (TGA) characterized the CF surface chemistry, wettability, and thermal stability. Specimens were prepared via injection molding and 3D printing processes, enabling systematic evaluation of tensile, flexural, and impact properties. Combined with Scanning Electron Microscopy observations of composite fracture surfaces, the study elucidates how modification treatments influence fiber–matrix interface bonding and mechanical enhancement mechanisms. The results indicate that after resizing treatment with silane coupling agents, the surface activity of CF and its interfacial compatibility with ABS were significantly improved, leading to a marked enhancement in the composite material’s overall performance. At a CF content of 9.62 wt%, the ABS-S-CF2 system exhibited optimal mechanical properties: The tensile strength and flexural strength of the injection-molded specimens reached 58.41 MPa and 81.51 MPa, respectively, representing increases of approximately 41.6% and 29.1% compared to neat ABS. The tensile strength and flexural strength of the printed specimens also reached 49.37 MPa and 80.19 MPa, respectively. Microstructural analysis indicates that the sizing treatment improves the interfacial bonding between CF and neat ABS.

Conventional knee orthoses (KOs) are fabricated from petroleum-based plastics and are difficult to recycle, while filament-based fused deposition modeling is limited by low deposition efficiency and weak interlayer strength for large load-bearing devices. Herein, the authors reported fused granular fabrication (FGF) of lightweight, biodegradable KOs from poly(lactic acid)/poly(butylene adipate-co-terephthalate)/bamboo fiber (PLA/PBAT/BF) composites. Composites with 2, 6, and 10 wt.% BF were melt-compounded using zinc acetate as a transesterification catalyst and directly granule-printed. Rheological and morphological analyses revealed that increasing BF loading raised melt viscosity and elasticity, albeit with local fiber aggregation. Tensile strength decreased from 37.0 to 26.0 MPa with fiber addition, whereas notched impact strength improved from 7.2 to 11.6 kJ/m², attributed to fiber pull-out, interfacial debonding, and matrix plastic deformation. A demonstration KO weighing only 243 g was printed. Printability depended strongly on nozzle temperature and speed: at 40 mm/s, all BF loadings failed, whereas 10 wt.% BF achieved defect-free printing at 220 °C and 30 mm/s. An optimal processing window of 10 wt.% BF, 190–220 °C, and 30 mm/s yielded tough, lightweight, biodegradable, custom-fit orthoses, demonstrating promising potential for rehabilitation applications.