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arXiv 2304.04892cond-mat.soft
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一种用于速率增硬软聚合物准静态至高应变率响应的大变形模型

A large deformation model for quasi-static to high strain rate response of a rate-stiffening soft polymer

Aditya Konale, Zahra Ahmed, Piyush Wanchoo, Vikas Srivastava

AI总结:

针对聚硼硅氧烷(PBS)大应变响应缺乏宽应变率本构模型的问题,提出基于微观物理的动态交联本构模型,通过实验验证其在六个数量级应变率下的预测准确性,可推广至同类软聚合物。

摘要:

聚硼硅氧烷(PBS)是一种重要的速率增硬软聚合物,具有动态可逆交联键,应用范围涵盖自修复传感与驱动、人体及结构防护等领域。其高度依赖速率的响应特性,尤其是对于抗冲击结构而言十分重要。然而,PBS的大应变响应尚未在准静态至高应变率范围内得到表征。目前,尚无能够预测PBS强速率相关大变形弹黏塑性响应的本构模型。为填补这一空白,我们针对PBS及其他具有动态交联键的同类软聚合物和聚合物凝胶,开发了一种受微观结构物理启发的本构模型,用于预测其大应变、非线性加载-卸载以及显著的速率相关响应。我们在10⁻³ s⁻¹到10³ s⁻¹的宽应变率范围内,对PBS开展了真应变约125%的压缩实验。该模型能够较为准确地捕捉PBS在六个数量级应变率范围内的响应。我们提出,PBS中存在两种交联机制:一种是宏观弛豫时间尺度τ≈3 s的硼-氧配位键动态交联,另一种是高应变率下作为交联键起作用、τ≈0.0005 s的临时缠结锁止。我们还提出了一种数值更新流程,用于求解由动态交联动力学产生的类卷积时间积分。我们通过涉及三维非均匀变形的实验验证了该模型及其有限元实现的预测能力。该建模框架可推广应用于其他微观结构与PBS相似的动态交联速率增硬软聚合物和聚合物凝胶。

英文摘要:

Polyborosiloxane (PBS) is an important rate-stiffening soft polymer with dynamic, reversible crosslinks used in applications ranging from self-healing sensing and actuation to body and structural protection. Its highly rate-dependent response, especially for impact-mitigating structures, is important. However, the large strain response of PBS has not been characterized over quasi-static to high strain rates. Currently, there are no constitutive models that can predict the strongly rate-dependent large-deformation elastic-viscoplastic response of PBS. To address this gap, we have developed a microstructural physics motivated constitutive model for PBS and similar soft polymers and polymer gels with dynamic crosslinks to predict their large strain, non-linear loading-unloading, and significantly rate-dependent response. We have conducted compression experiments on PBS up to true strains of $\sim$125$\%$ over a wide strain rate range of 10$^{-3}$ s$^{-1}$ to 10$^{3}$ s$^{-1}$. The model reasonably accurately captures the response of PBS over six decades of strain rates. We propose boron-oxygen coordinate-bond dynamic crosslinks with macroscopic relaxation timescale $τ\approx 3$ s and temporary entanglement lockups at high strain rates acting as crosslinks with $τ\approx 0.0005$ s as the two types of crosslink mechanisms in PBS. We have outlined a numerical update procedure to evaluate the convolution-like time integrals arising from dynamic crosslink kinetics. Experiments involving three-dimensional inhomogeneous deformations were used to verify the predictive capabilities of our model and its finite element implementation. The modeling framework can be adopted for other dynamically crosslinked rate-stiffening soft polymers and polymer gels that are microstructurally similar to PBS.

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