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The flame retardancy of wood–polymer composites significantly affects their potential applications. Thus, multilayered wood flour/high-density polyethylene (HDPE)/polycarbonate (PC) composites were prepared via thermocompression to improve the fire retardancy of wood–polymer composites in this paper. Thermal degradation behavior, flame retardancy, and flexural strengths of the resulting composites were investigated using a thermogravimetric analysis, cone calorimetry, and mechanical testing machine, respectively. Results revealed that the boric acid treatment reduced the heat release rate and total heat release of the wood flour/HDPE composites and increased their mass of residues. However, boric acid reduced the flexural strength of the resulting composites. The combustion test indicated that PC cap layers suppressed the combustion of the resulting composites via the formation of carbon layers. Adding PC layers reduced heat release and increased the flexural strength of the resulting composites. Finally, the failure mode of the multilayered wood flour/HDPE/PC composites in the three-point flexural test was simulated by finite element analysis. [ABSTRACT FROM AUTHOR]

Abstract Wood plastic composites (WPCs) have emerged as environmentally benign filaments for fused deposition modeling (FDM) printing. Using WPCs filaments to print light weight and strong cellular structures could create new application potentials for WPCs and provide sustainable feedstock for cellular materials. In this research, the compression performance of FDM printed circle, square, and voronoi WPCs cellular structures were investigated using finite element simulations and compression experiments. Simulated results did not agree with experimental results due to the presence of cavities in the prints. Cavities were formed in the cellular structures with arcs and curvature. The results showed that the circle cellular structure demonstrated great fluctuations between the simulations and experimental results. The cavity porosity was also found to increase with the increase of the print line width. Further, to improve the accuracy of simulations, the cavity porosity exists in the cellular structures was considered while revising the models. After modification, square cellular models compressed the least, followed by the circle and voronoi ones, which was consistent with the experimental results. Minimizing the print line width could reduce cavity porosity. Nonetheless, thinner print line width and smaller wood fiber size in filaments will likely increase manufacturing cost and difficulty. [ABSTRACT FROM AUTHOR]

Non-powered adaptive systems are attractive in the construction of environment actuators, meteorosensitive architectures, biomedical devices, and soft robotics. Combining hydrophilic materials and anisotropic structures to mimic self-morphing plant structures has been demonstrated as an effective approach to creating artificial hygromorphs. The convenience of 3D printing technologies in shaping programmable complex structures facilitates the imitation of complex anisotropic plant structures. In this research, we constructed a bio-hygromorph using fish swim bladder hydrogel as the hydrophilic material and wood flour-filled polylactic acid (WPLA) scaffold, which was printed with fused deposition modeling (FDM) 3D printing technology (3DP). The environmental benign bio-hygromorph displayed morphing abilities triggered by moisture content changes, as the fish swim bladder hydrogel swelled and shrunk during absorption and desorption cycles. The strain disproportion of the two-layered composite structure in the bio-hygromorph drove the bending deformation. Stress analyses performed with finite element analysis (FEA) also revealed the mechanism behind the moisture content driven morphing of the bio-hygromorph. Notably, the bio-hygromorph exhibited faster response times to moisture absorption than desorption, which may donate actuators' different attributes in distinct moisture conditions. [ABSTRACT FROM AUTHOR]