Use of Wood in Additive Manufacturing: Review and Future Prospects

Innovative Approaches for Manufacturing Epoxy-Modified Wood and Cellulose Fiber Composites: A Comparison between Injection Molding and 3D Printing

The current study focused on improving the properties of polylactic acid (PLA) for wider application in load-bearing scenarios. Various methods were explored to optimize the interaction between PLA and natural fibers, particularly wood fibers (WFs). Alkalized and epoxy-impregnated WFs were evaluated against untreated WFs and cellulose fibers in both injection molding (IM) and fused deposition modeling (FDM). FTIR analysis revealed the removal of hemicellulose and lignin in alkalized WFs and uniform epoxy curing. Addition of fibers reduced PLA's thermal stability while acting as nucleating agents. Additionally, fibers augmented the storage modulus of biocomposites, with alkalized fibers exhibiting the highest tensile modulus in IM. FDM samples with a 0° raster angle showed superior impact resistance compared to IM counterparts. Moreover, raster angle significantly influenced FDM biocomposite properties, enhancing the tensile strength and modulus of untreated WF and cellulose fibers at 0°. Although FDM did not produce alkalized WF samples, epoxy impregnation emerged as a promising method for enhancing PLA/WF composite mechanical properties in the IM process, offering valuable insights for composite material development.

Biotechnology to reduce logistics burden and promote environmental stewardship for Air Force civil engineering requirements

This review provides discussion of advances in biotechnology with specific application to civil engineering requirements for airfield and airbase operations. The broad objectives are soil stabilization, waste management, and environmental protection. The biotechnology focal areas address (1) treatment of soil and sand by biomineralization and biopolymer addition, (2) reduction of solid organic waste by anaerobic digestion, (3) application of microbes and higher plants for biological processing of contaminated wastewater, and (4) use of indigenous materials for airbase construction and repair. The consideration of these methods in military operating scenarios, including austere environments, involves comparison with conventional techniques. All four focal areas potentially reduce logistics burden, increase environmental sustainability, and may provide energy source, or energy-neutral practices that benefit military operations.

Sound Absorption Performance and Mechanical Properties of the 3D-Printed Bio-Degradable Panels

The 3D printing process allows complex structures to be obtained with low environmental impact using biodegradable materials. This work aims to develop and acoustically characterize 3D-printed panels using three types of materials, each manufactured at five infill densities (20%, 40%, 60%, 80% and 100%) with three internal configurations based on circular, triangular, and corrugated profiles. The highest absorption coefficient values (α = 0.93) were obtained from the acoustic tests for the polylactic acid material with ground birch wood particles in the triangular configuration with an infill density of 40%. The triangular profile showed the best acoustic performance for the three types of materials analysed and, from the point of view of the mechanical tests, it was highlighted that the same triangular configuration presented the highest resistance both to compression (40 MPa) and to three-point bending (50 MPa). The 40% and 60% infill density gave the highest absorption coefficient values regardless of the material analyzed. The mechanical tests for compression and three-point bending showed higher strength values for samples manufactured from simple polylactic acid filament compared to samples manufactured from ground wood particles. The standard defects of 3D printing and the failure modes of the interior configurations of the 3D-printed samples could be observed from the microscopic analysis of the panels. Based on the acoustic results and the determined mechanical properties, one application area for these types of 3D-printed panels could be the automotive and aerospace industries.

Biomass 3D Printing: Principles, Materials, Post-Processing and Applications

Under the background of green and low-carbon era, efficiently utilization of renewable biomass materials is one of the important choices to promote ecologically sustainable development. Accordingly, 3D printing is an advanced manufacturing technology with low energy consumption, high efficiency, and easy customization. Biomass 3D printing technology has attracted more and more attentions recently in materials area. This paper mainly reviewed six common 3D printing technologies for biomass additive manufacturing, including Fused Filament Fabrication (FFF), Direct Ink Writing (DIW), Stereo Lithography Appearance (SLA), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM) and Liquid Deposition Molding (LDM). A systematic summary and detailed discussion were conducted on the printing principles, common materials, technical progress, post-processing and related applications of typical biomass 3D printing technologies. Expanding the availability of biomass resources, enriching the printing technology and promoting its application was proposed to be the main developing directions of biomass 3D printing in the future. It is believed that the combination of abundant biomass feedstocks and advanced 3D printing technology will provide a green, low-carbon and efficient way for the sustainable development of materials manufacturing industry.