Rate-dependent failure mechanism of elastomers

Brighenti, Roberto; Vernerey, Franck J.; Artoni, Federico

doi:10.1016/j.ijmecsci.2017.05.033

Cited by 12 publications

(6 citation statements)

References 44 publications

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“…While extension-dependent rate coefficients have been previously considered for polymer networks (Green and Tobolsky, 1946;Tanaka and Edwards, 1992b), exact relations have not yet been discovered, leaving models to assume they are constant (Green and Tobolsky, 1946;Vernerey et al, 2017;Brighenti et al, 2017;Vernerey, 2018;Guo and Long, 2020), or assume some other form (Tanaka and Edwards, 1992a;Lavoie et al, 2016;Yu et al, 2018;Shen and Vernerey, 2020;Lin et al, 2020;Lu et al, 2020;Guo and Zaïri, 2021) typically inspired by or in some way similar to the model of Bell (1978). Eqs.…”

Section: Transition State Theorymentioning

confidence: 99%

“…Transient network theory is typically attributed to Tanaka and Edwards (1992b,a), which is built upon foundational work from the 1940s to the 1990s (Green and Tobolsky, 1946;Flory, 1960;Thomas, 1966;Fricker, 1973). Recent development has been driven by Vernerey et al (2017;2018), and has lead to successful application in fracture scenarios (Brighenti et al, 2017;Shen and Vernerey, 2020). Other constitutive models for polymers with dynamic bonds combine physically-based insights with continuum-level constitutive laws, such those for the mechanics of dual-crosslink gels and of networks with temperature-sensitive dynamic covalent bonds (Meng et al, 2016;Yu et al, 2018;Lin et al, 2020;Hui and Long, 2012;Long et al, 2014;Guo et al, 2016;Lu et al, 2020;Long et al, 2013;Long, 2014;Sun et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Chain breaking in the statistical mechanical constitutive theory of polymer networks

Buche,

Silberstein

2021

Preprint

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Elastomers are used in a wide range of applications because of their large strain to failure, low density, and tailorable stiffness and toughness. The mechanical behavior of elastomers derives mainly from the entropic elasticity of the underlying network of polymer chains. Elastomers under large deformation experience bonds breaking within the backbone chains that constitute the polymer network. This breaking of chains damages the network, can lead to material failure, and can be utilized as an energy dissipation mechanism. In the case of reversible bonds, broken chains may reform and heal the damage in the network. If the reversible bonds are dynamic, chains constantly break and reform and create a transient network. A fundamental constitutive theory is developed to model the mechanics of these polymer networks. A statistical mechanical derivation is conducted to yield a framework that takes in an arbitrary single-chain model (a Hamiltonian) and outputs the following: the single-chain mechanical response, the breaking and reforming kinetics, the equilibrium distribution of chains in the network, and the partial differential equations governing the deformationcoupled network evolution. This statistical mechanical framework is then brought into the continuum scale by using macroscopic thermodynamic constitutive theory to obtain a constitutive relation for the Cauchy stress. The potential-supplemented freely jointed chain (uFJC) model is introduced, and a parametric study of its mechanical response and breaking kinetics is provided. This single-chain model is then implemented within the constitutive framework, which we specialize and apply in two exemplary cases: the mechanical response and irreversible breakdown of a multinetwork elastomer, and the mechanical response of a dual crosslink gel. After providing a parametric study of the general constitutive model, we apply it to a hydrogel with reversible metal-coordination crosslinks. In several cases, we find that the breakdown of the network causes secondary physical mechanisms to become important and inhibit the accuracy of our model. We then discuss these mechanisms and indicate how our existing framework can be adjusted to incorporate them in the future.

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Section: Transition State Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chain breaking in the statistical mechanical constitutive theory of polymer networks

Buche,

Silberstein

2021

Preprint

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“…On the other hand, the capability to modulate their toughness or viscosity has promoted a wide attention in advanced applications (from materials science to bioengineering) where such materials can be conveniently exploited to get smart and functional materials such as artificial muscles, active and self-morphing materials [3,4]. Furthermore, highly deformable materials often exhibit a rate-dependent response [5,6], and in some cases (such as for natural rubbers) when sufficiently stretched at room temperature, show a strain-induced crystallization inducing a change S from an amorphous into a semicrystalline-like microstructural configuration due to the appearance of a highly oriented microstructure developing along the tensile direction [7]. The microstructure of polymer materials is fully amorphous and, at the molecular level, is formed by a three-dimensional network of polymer chains linked at several discrete points (cross-links).…”

Section: Introductionmentioning

confidence: 99%

Crack paths in soft thin sheets

Brighenti

Carpinteri

Artoni

2019

Frattura Ed Integrità Strutturale

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Highly deformable materials (elastomers, gels, biological tissues, etc.) are ubiquitous in nature as well as in technology. The understanding of their flaw sensitivity is crucial to ensure a desired safety level. Fracture failure in soft materials usually occurs after the development of an uncommon crack path because of the non-classical near-tip stress field and the viscous effects. In a neo-Hookean material, the true opening stress singularity along the crack path (evaluated normal to the crack line) is of the order 2 r  , while it is of the order 1/2 s  ahead of the crack tip, promoting the appearance of a crack tip splitting leading to a tortuous crack. In the present paper, experimental tests concerning the fracture behavior of highly deformable thin sheets under tension are discussed, and the observed crack paths are interpreted according to the crack tip stress field arising for large deformations. The study reveals that higher strain rates facilitate the development of a simple Mode I crack path, while lower strain rates induce a mixed Mode in the first crack propagation stage, leading to the formation of new crack tips. The above described behavior seems to not be affected by the initial crack size.

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“…However, the presence of defects or flaws can severely hinder their load bearing capacity or their deformation ability, and therefore the quantitative assessment of the influence of geometric imperfections on their mechanical response and ultimate limit state becomes crucial for the design and the evaluation of their safety level under service conditions, also considering the effects of temperature …”

Section: Introductionmentioning

confidence: 99%

“…However, the presence of defects or flaws [11][12][13] can severely hinder their load bearing capacity or their deformation ability, and therefore the quantitative assessment of the influence of geometric imperfections on their mechanical response and ultimate limit state becomes crucial for the design and the evaluation of their safety level under service conditions, also considering the effects of temperature. 14,15 Soft materials, showing high stretchability, have the capability to tolerate the presence of defects without failure because of the rearrangement of their network occurring at the microscale, leading to a reduction of the local stress state.…”

Section: Introductionmentioning

confidence: 99%

Defect sensitivity of highly deformable polymeric materials with different intrinsic qualities at various strain rates

Brighenti

Carpinteri

Artoni

et al. 2017

Fatigue Fract Eng Mat Struct

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Highly deformable materials, such as elastomers and gels, can withstand very large deformation without failure, and this response is usually insensitive to the presence of macroscopic defects. These polymer‐based materials, different from the traditional ones which are usually characterized by an enthalpic elasticity, show a mechanical response which is governed by the state of internal entropy of their molecular network. If fracture energy is large, the noticeable ability of soft materials to rearrange their network at the microscale, to display large deformation and to dissipate energy thanks to their viscoelasticity, allows the minimization of the local detrimental effect of existing flaws. In the present paper, the mechanical behavior of silicone‐based edge cracked plates with different crack sizes and severity of the intrinsic flaws embedded in the material is examined by taking into account the time‐dependent effects. Experimental and theoretical aspects are discussed to explain the defect tolerance of such materials. The detrimental effect of intrinsic voids is quantified, and the beneficial effect due to strain at low rates is analysed. The critical distance is related to the ultimate stretch value, the quality of the material, and the crack size.

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Rate-dependent failure mechanism of elastomers

Cited by 12 publications

References 44 publications

Chain breaking in the statistical mechanical constitutive theory of polymer networks

Chain breaking in the statistical mechanical constitutive theory of polymer networks

Crack paths in soft thin sheets

Defect sensitivity of highly deformable polymeric materials with different intrinsic qualities at various strain rates

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