Amiri Ali, Yu Arvin, Webster Dean, Ulven Chad
Department of Mechanical Engineering, North Dakota State University, Fargo, ND 58102, USA.
Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND 58102, USA.
Polymers (Basel). 2016 Apr 19;8(4):153. doi: 10.3390/polym8040153.
With the increase in structural applications of bio-based composites, the study of long-term creep behavior of these materials turns into a significant issue. Because of their bond type and structure, natural fibers and thermoset resins exhibit nonlinear viscoelastic behavior. Time-temperature superposition (TTS) provides a useful tool to overcome the challenge of the long time required to perform the tests. The TTS principle assumes that the effect of temperature and time are equivalent when considering the creep behavior, therefore creep tests performed at elevated temperatures may be converted to tests performed at longer times. In this study, flax fiber composites were processed with a novel liquid molding methacrylated epoxidized sucrose soyate (MESS) resin. Frequency scans of flax/MESS composites were obtained at different temperatures and storage modulus and loss modulus were recorded and the application of horizontal and vertical shift factors to these viscoelastic functions were studied. In addition, short-term strain creep at different temperatures was measured and curves were shifted with solely horizontal, and with both horizontal and vertical shift factors. The resulting master curves were compared with a 24-h creep test and two extrapolated creep models. The findings revealed that use of both horizontal and vertical shift factors will result in a smoother master curves for loss modulus and storage modulus, while use of only horizontal shift factors for creep data provides acceptable creep strain master curves. Based on the findings of this study, flax/MESS composites can be considered as thermorheologically complex materials.
随着生物基复合材料在结构应用中的增加，对这些材料长期蠕变行为的研究成为一个重要问题。由于其粘结类型和结构，天然纤维和热固性树脂表现出非线性粘弹性行为。时间-温度叠加（TTS）提供了一个有用的工具来克服进行测试所需的长时间挑战。TTS原理假设在考虑蠕变行为时温度和时间的影响是等效的，因此在高温下进行的蠕变测试可以转换为在更长时间下进行的测试。在本研究中，亚麻纤维复合材料采用新型液体模塑甲基丙烯酸化环氧大豆油蔗糖酯（MESS）树脂进行加工。在不同温度下获得亚麻/ MESS复合材料的频率扫描，并记录储能模量和损耗模量，并研究了水平和垂直移位因子在这些粘弹性函数中的应用。此外，测量了不同温度下的短期应变蠕变，并仅用水平移位因子以及同时用水平和垂直移位因子对曲线进行移位。将所得的主曲线与24小时蠕变试验和两个外推蠕变模型进行比较。研究结果表明，同时使用水平和垂直移位因子将导致损耗模量和储能模量的主曲线更平滑，而仅对蠕变数据使用水平移位因子可提供可接受的蠕变应变主曲线。基于本研究的结果，亚麻/ MESS复合材料可被视为热流变复杂材料。
