Shear yielding and crazing in dry and wet amorphous PLA at body temperature
Shear yielding and crazing in dry and wet amorphous PLA at body temperature
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DOI：
10.1016/j.polymer.2023.126477
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发表时间：
2023-11-17
期刊：
影响因子：
4.6
通讯作者：
Brassart，Laurence
中科院分区：
文献类型：
--
作者：
Chen，Huanming;Pan，Zhouzhou;Brassart，Laurence
了解生物降解聚合物的非弹性、速率依赖性力学响应对于设计具有受控变形和失效响应的承载生物降解结构非常重要。在这项研究中，我们调查的机械响应的无定形聚乳酸（PLA）在干燥和潮湿的条件下，在体温降解开始之前。水的存在使玻璃化转变温度降低4.5 °C，储能模量降低21%，并且压缩和拉伸屈服强度降低约10%，尽管吸水量为0.93重量%。PLA的拉伸响应主要是银纹屈服，而不是剪切塑性，是稳定的颈缩，尽管显着的应变软化和局部应变不均匀性测量的数字图像相关（DIC）。进一步分析的DIC应变场在干燥和潮湿的样品表明，从纯银纹屈服在干燥的样品银纹屈服和剪切塑性在潮湿的样品共存的过渡。拉伸和压缩行为之间的机制转换的干和湿PLA的承载结构的设计和本构建模的影响。
Understanding the inelastic, rate-dependent mechanical response of biodegradable polymers is important for the design of load-bearing biodegradable structures with controlled deformation and failure response. In this study, we investigate the mechanical response of amorphous polylactic acid (PLA) in dry and wet conditions prior to the onset of degradation at body temperature. The presence of water decreases the glass transition temperature by 4.5 °C, the storage modulus by 21%, and the compressive and tensile yield strengths by about 10%, despite a small water uptake of 0.93 wt%. The tensile response of PLA is dominated by craze yielding, rather than shear plasticity, and is stable against necking despite pronounced strain softening and local strain heterogeneities measured by Digital Image Correlation (DIC). Further analysis of the DIC strain fields in dry and wet samples suggests a transition from pure craze yielding in dry samples to a coexistence of craze yielding and shear plasticity in wet samples. The mechanism shift between tension and compression behaviour of dry and wet PLA has implications for the design of load-bearing structures and for constitutive modelling.