This paper presents the design and fabrication of a magnetic double network (DN) composite, which consists of permanent magnet chains embedded in an elastomer matrix, and was capable of large yet fully recoverable deformation. The initially connected magnets served as reusable sacrificial components in the composite. The strong magnetic attraction between neighboring magnetics endowed the composite with the high strength while the compliance of the elastomer matrix provided the high extensibility. Having a similar mechanism as DN gels, the composite was found to be significantly tougher than either of the constituents. The nonlinear behavior in the composite separated it into two coexisting phases – a softer phase with separated magnet links and a stiffer phase with connected magnet links – which led to the stress plateau on the tensile curve. Further stretching was manifested by the growth of the disconnected softer phase at the expense of the linked stiffer phase, until all magnets were separated. The unloading curves appeared drastically different from the loading curves, as the force needed to separate two magnets was much higher than the force at which two separated magnets snapped back. Such asymmetry between loading and unloading was the main cause of the hysteresis in the stress–strain curve and the energy dissipation. To further understand the physical mechanism and the damage process of the magnetic DN composite, a simple model was developed to examine the deformation and damage dissipation process of composite. With very few parameters, the model predictions agree qualitatively with the measured properties of the material, and the difference can be further reduced by accounting for the interfacial friction/adhesion, a second means of energy dissipation. With a combination of desired properties including high stretchability, self-healing, and high toughness, the magnetic DN composite is a viable candidate for various applications.

中文翻译：

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可恢复变形大的磁性双网复合材料

本文介绍了一种磁双网（DN）复合材料的设计和制造，该复合材料由嵌入弹性体基质中的永磁链组成，具有较大的变形能力，但可完全恢复。最初连接的磁体充当复合材料中可重复使用的牺牲组件。相邻磁性材料之间的强磁性吸引力使复合材料具有高强度，而弹性体基质的柔韧性提供了高延展性。具有与DN凝胶相似的机理，发现该复合材料比任何一种成分都坚韧得多。复合材料中的非线性行为将其分成两个共存的阶段-磁链分开的较软相和磁链相连的较硬相-导致了拉伸曲线上的应力平稳期。通过断开的较软相的生长，以连接的较硬相为代价，表明了进一步的拉伸，直到所有磁体都被分离为止。卸载曲线看上去与加载曲线完全不同，因为分离两个磁体所需的力远大于两个分离的磁体折回时的力。装卸之间的这种不对称是应力-应变曲线和能量耗散产生滞后的主要原因。为了进一步了解磁性DN复合材料的物理机理和破坏过程，建立了一个简单的模型来检查复合材料的变形和破坏耗散过程。只需很少的参数，模型预测就可以与材料的测量特性定性地吻合，并且可以通过考虑界面摩擦/附着力（一种第二耗能手段）来进一步减小差异。结合所需的特性（包括高拉伸性，自修复性和高韧性），磁性DN复合材料是各种应用的可行选择。