Toughening and reinforcement mechanism of multi-scale HA/HDPE composite
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摘要: 通过电镜分析及理论推导对羟基磷灰石( Hydroxyapatite, HA) /高密度聚乙烯( High density polyethylene, HDPE) 复合材料界面粘结状态、HA 颗粒对裂纹扩展的钝化、钉扎作用、复合纤维对体系分子热激活能的影响及复合纤维的能量吸收机制与增强增韧等进行了深入研究。结果表明: HA/HDPE 复合材料通过纳米HA 颗粒与 HA/HDPE 复合纤维在不同尺度上协同作用达到增强增韧的效果。即在纳米尺度, 纳米HA 颗粒的均匀分散和高的HA/HDPE 界面结合强度显著提高了HDPE 的结晶度, 细化了HDPE 晶粒尺寸, 并在HA 颗粒表面形成取向结晶层, 从而使材料在断裂过程中通过HDPE 取向结晶层的基体形变和HA 脱粘过程对微裂纹起钝化和钉扎作用, 并扩大能量耗散的区域, 以阻滞微孔隙和银纹的长大和破断, 抑制大裂纹的早期形成。在微米尺度, 由于HA/HDPE 复合纤维的定向排列, 使体系的活化体积显著降低, 大大增加了材料的断裂热激活能, 从而显著提高材料的强度。另一方面, 复合纤维在应力作用过程中通过纤维断裂、纤维拔出、裂纹偏转机制使材料在形变与破坏过程中耗散更多的能量, 从而显著提高材料的强度和韧性。
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关键词:
- HA/HDPE 复合材料 /
- 多尺度结构 /
- 强韧化机制
Abstract: The toughening and reinforcement mechanism of HA ( hydroxyapatite ) /HDPE ( high density polyethylene ) composite was investigated. The results show that the co-operative actions of multi-scale is the main role to enhance the mechanical properties. On the nano-scale, the homogeneous dispersion of HA and high interfacial strength between HA and HDPE leads to the high crystalline, litter crystal size and the formation of oriented extended-chain crystal structure. This will result in the HDPE deformation and HA deadhesion during the fracture process, which can pin the development of microcracks, expend large energies and prohibit the formation of large crack. On the micro-scale, the formation of oriented HA/HDPE fibers can greatly reduce the activity volume and increase the fracture energy, which leads to the high st rength. On the other hand, the composite fiber can expend much more energy by fracture, pullout and crackbowing, which enhances the strength and toughness to a great extent. -
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