Crosslinking degree variations enable programming and controlling soft fracture via sideways cracking

IF 9.4 1区 材料科学 Q1 CHEMISTRY, PHYSICAL
Miguel Angel Moreno-Mateos, Paul Steinmann
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Abstract

Large deformations of soft materials are customarily associated with strong constitutive and geometrical nonlinearities that originate new modes of fracture. Some isotropic materials can develop strong fracture anisotropy, which manifests as modifications of the crack path. Sideways cracking occurs when the crack deviates to propagate in the loading direction, rather than perpendicular to it. This fracture mode results from higher resistance to propagation perpendicular to the principal stretch direction. It has been argued that such fracture anisotropy is related to deformation-induced anisotropy resulting from the microstructural stretching of polymer chains and, in strain-crystallizing elastomers, strain-induced crystallization mechanisms. However, the precise variation of the fracture behavior with the degree of crosslinking remains to be understood. Leveraging experiments and computational simulations, here we show that the tendency of a crack to propagate sideways in the two component Elastosil P7670 increases with the degree of crosslinking. We explore the mixing ratio for the synthesis of the elastomer that establishes the transition from forward to sideways fracturing. To assist the investigations, we construct a novel phase-field model for fracture where the critical energy release rate is directly related to the crosslinking degree. Our results demonstrate that fracture anisotropy can be modulated during the synthesis of the polymer. Then, we propose a roadmap with composite soft structures with low and highly crosslinked phases that allow for control over fracture, arresting and/or directing the fracture. The smart combination of the phases enables soft structures with enhanced fracture tolerance and reduced stiffness. By extending our computational framework as a virtual testbed, we capture the fracture performance of the composite samples and enable predictions based on more intricate composite unit cells. Overall, our work offers promising avenues for enhancing the fracture toughness of soft polymers.

Abstract Image

软材料的大变形通常与强构造和几何非线性有关,这些非线性会产生新的断裂模式。某些各向同性材料会产生强烈的断裂各向异性,表现为裂纹路径的改变。当裂纹偏离加载方向而不是垂直于加载方向扩展时,就会出现侧向裂纹。这种断裂模式是由于垂直于主要拉伸方向的扩展阻力较大。有观点认为,这种断裂各向异性与聚合物链微结构拉伸导致的变形诱导各向异性有关,在应变结晶弹性体中,则与应变诱导结晶机制有关。然而,断裂行为随交联程度的精确变化仍有待了解。通过实验和计算模拟,我们在此表明,在双组分 Elastosil P7670 中,裂纹向侧面扩展的趋势会随着交联度的增加而增加。我们探索了合成弹性体的混合比例,该比例决定了裂纹从正向扩展到侧向扩展的过渡。为了协助研究,我们构建了一个新颖的断裂相场模型,其中临界能量释放率与交联度直接相关。我们的研究结果表明,断裂各向异性可在聚合物合成过程中进行调节。然后,我们提出了一种具有低交联相和高交联相的复合软结构路线图,这种结构可以控制断裂、阻止和/或引导断裂。各相的巧妙组合可使软结构具有更强的断裂耐受性和更低的刚度。通过将我们的计算框架扩展为虚拟试验台,我们可以捕捉到复合材料样品的断裂性能,并根据更复杂的复合材料单元单元进行预测。总之,我们的工作为提高软聚合物的断裂韧性提供了前景广阔的途径。
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来源期刊
npj Computational Materials
npj Computational Materials Mathematics-Modeling and Simulation
CiteScore
15.30
自引率
5.20%
发文量
229
审稿时长
6 weeks
期刊介绍: npj Computational Materials is a high-quality open access journal from Nature Research that publishes research papers applying computational approaches for the design of new materials and enhancing our understanding of existing ones. The journal also welcomes papers on new computational techniques and the refinement of current approaches that support these aims, as well as experimental papers that complement computational findings. Some key features of npj Computational Materials include a 2-year impact factor of 12.241 (2021), article downloads of 1,138,590 (2021), and a fast turnaround time of 11 days from submission to the first editorial decision. The journal is indexed in various databases and services, including Chemical Abstracts Service (ACS), Astrophysics Data System (ADS), Current Contents/Physical, Chemical and Earth Sciences, Journal Citation Reports/Science Edition, SCOPUS, EI Compendex, INSPEC, Google Scholar, SCImago, DOAJ, CNKI, and Science Citation Index Expanded (SCIE), among others.
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