Interfacial mechanical behavior of wood fiber/high density polyethylene composites based on digital image correlation
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摘要: 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。Abstract: 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.
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表 1 木纤维/高密度聚乙烯(WF/HDPE)复合材料组分配比
Table 1. Mass fractions of components of wood fiber/high density polyethylene(WF/HDPE) composites
Sample Mass fraction of HDPE/wt% Mass fraction of wood fiber/wt% Mass fraction of mAPP/wt% 10WF/HDPE 90 10 − 20WF/HDPE 80 20 − 30WF/HDPE 70 30 − 40WF/HDPE 60 40 − 10mAPP-30WF/HDPE 60 30 10 15mAPP-30WF/HDPE 55 30 15 20mAPP-30WF/HDPE 50 30 20 25mAPP-30WF/HDPE 45 30 25 Note: mAPP—Modified ammonium polyphosphate. -
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