基于数字图像相关技术的木纤维/高密度聚乙烯复合材料界面力学行为

以木纤维/高密度聚乙烯(WF/HDPE)复合材料界面应变为研究对象，采用数字图像相关技术(DIC)探究WF(质量分数为10wt%~40wt%)及改性聚磷酸铵(mAPP)阻燃剂(质量分数为10wt%~25wt%)对WF/HDPE复合材料应变分布及传递的演变规律，并结合力学性能测试和SEM对其拉伸性能、冲击性能、界面结合进行分析。结果表明:随着WF添加量从10wt%增至30wt%，WF/HDPE复合材料应变传递较为平稳，由受力两端向复合材料轴中心均匀传递，当WF添加量为30wt%时，高应变在复合材料上约1/2区域得到了有效传递，此时，复合材料的拉伸强度和冲击强度分别达21.5 MPa和10.22 kJ/m2。但当WF添加量增加至40wt%时，WF/HDPE复合材料的拉伸承载端部出现应力集中，阻碍了其内部应变的均匀传递。mAPP阻燃剂加剧了WF与HDPE界面间的脱粘行为，削弱了WF与HDPE之间的机械啮合作用力。当mAPP阻燃剂添加量从10wt%增加至25wt%时，WF/HDPE复合材料开始出现多个分散的高应变区域，全场应变传递出现不规则分布。当mAPP阻燃剂添加量达25wt%时，WF/HDPE复合材料应变分布呈两极化趋势，导致复合材料的拉伸强度和冲击强度分别降低为15.5 MPa和5.49 kJ/m2。 

Interfacial mechanical behavior of wood fiber/high density polyethylene composites based on digital image correlation

The interfacial strain of wood fiber/high density polyethylene(WF/HDPE) composites was studied. Digital image correlation(DIC) was used to investigate the effects of WF mass fraction (10wt%–40wt%) and modified ammonium polyphosphate(mAPP) flame retardant mass fraction (10wt%–25wt%) on the strain distribution and transmission evolution of WF/HDPE composites. The mechanical properties and interfacial bonding of WF/HDPE composites were analyzed by mechanical tests and SEM, respectively. With WF mass fraction rising from 10wt% to 30wt%, the strain transfers stably and uniformly from both ends to the axial center of the WF/HDPE composite. When the WF amount reaches 30wt%, the high strain transfers within 1/2 region of WF/HDPE composite and its tensile strength and impact strength are 21.5 MPa and 10.22 kJ/m2, respectively. However, when WF mass fraction is 40wt%, the stress concentration occurs at tensile bearing end of the WF/HDPE composite, and prevents uniform transmission of strain in WF/HDPE composites. mAPP exacerbates debonding and impedes mechanical meshing between WF and HDPE. As WF mass fraction increases from 10wt% to 25wt%, several scattered high strain regions appear and the full-field strain transfers irregularly. When the WF mass fraction reaches 25wt%, the strain distribution of WF/HDPE composite becomes polarized, resulting in a decrease of the tensile strength and impact strength to 15.5 MPa and 5.49 kJ/m2, respectively.