Natural fiber/high-density polyethylene (HDPE) composites (NFPCs) were fabricated via extrusion using three types of natural fibers from poplar wood (PW), radiata pine (RP), and rice husk (RH), respectively. The specimens were cut from the extruded samples at various off-axis angles (from 0° to 90°). The effect of fiber geometry and orientation distribution on the mechanical properties, creep behavior, and thermal expansion of the NFPCs was investigated. The natural fibers in the composites showed a preferential orientation along the extrusion direction, as evidenced by the optics micrographs. The flexural properties and impact strength of the NFPCs were the highest at zero angle and decreased considerably with increasing orientation angle, which was further validated by the finite element analysis. At zero angle, the PW/HDPE composites had the highest flexural and impact strength and the smallest creep strain and thermal expansion, but a small difference in mechanical properties was observed at 90° among the NFPCs. The significant anisotropy of properties at various angles of the PW/HDPE composites was due to the high aspect ratio (L/D) of poplar wood fiber. These results indicate that high fiber L/D and orientation distribution had a beneficial effect on the properties of NFPCs.

天然纤维/高密度聚乙烯（HDPE）复合材料（NFPC）是通过挤压分别使用杨木（PW），辐射松（RP）和稻壳（RH）的三种天然纤维制成的。以不同的离轴角（从0°到90°）从挤出的样品上切下样品。研究了纤维几何形状和取向分布对NFPC力学性能，蠕变行为和热膨胀的影响。光学显微照片证明，复合材料中的天然纤维沿挤出方向显示出优先取向。NFPC的挠曲性能和冲击强度在零角处最高，并随着取向角的增加而显着降低，这已通过有限元分析进一步得到验证。在零角度时 PW / HDPE复合材料具有最高的弯曲强度和冲击强度，最小的蠕变应变和热膨胀率，但在NFPC中，在90°时观察到的机械性能差异很小。PW / HDPE复合材料在各种角度下的特性均具有显着的各向异性，这是由于杨木纤维的长径比（L / D）高。这些结果表明，高的纤维L / D和取向分布对NFPC的性能具有有益的影响。