Anomalous inflation of a nematic balloon

He, Qinghua; Zheng, Yue; Wang, Zhijian; He, Xuming; Cai, Shengqiang

doi:10.1016/j.jmps.2020.104013

Cited by 29 publications

(37 citation statements)

References 16 publications

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“…Pressurized cylindrical vessels are found in many technological applications: in oil and gas pipes [1,16], nuclear plants and also blood vessels, for example. The stability of pressure vessels under combined loading is an active area of research despite its long history [2,14,17,18], not all of which can be surveyed here as the literature spans at least four decades. Pertinent results are recalled here.…”

Section: Introductionmentioning

confidence: 99%

Fate of a bulge in an inflated hyperelastic tube: theory and experiment

2021

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Mechanical instability in a pre-tensioned finite hyperelastic tube subjected to a slowly increasing internal pressure produces a spatially localized bulge at a critical pressure. This instability is studied in controlled experiments on inflated latex rubber tubes, from the perspective of buckling observed in aneurysms and their rupture risk. The fate of the bulge under continued inflation is governed by the end-conditions and the initial tension in the tube. In a tube with one end fixed and a weight attached to the other freely moving end, the bulge propagates axially at low initial tension, growing in length, and the tube relaxes by extension without buckling. Rupture occurs when the tension is high. By contrast, the bulge formed in an initially stretched tube held fixed at both its ends can buckle or rupture, depending on the amount of initial tension. Experiments are reported for different initial tensions and boundary conditions (BCs). Failure maps in the stretch parameter space and in stretch–tension space are constructed by extending existing theories for bulge formation and buckling analyses to the experimentally relevant BCs. Failure maps deduced from the theory are compared against experiments, and the underlying assumptions are critically assessed. Experiments reveal that buckling provides an alternative route to relieve the stress built up during inflation. Hence, buckling, when it occurs, can be a protective fail-safe mechanism against the rupture of a bulge in an inflated elastic tube.

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Section: Introductionmentioning

confidence: 99%

Fate of a bulge in an inflated hyperelastic tube: theory and experiment

2021

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“…We explore the response of a cylindrical shell made of a nematic elastomer and study how the isotropic-nematic phase transition affects this instability. We note here that He et al [12] have studied the anomalous behavior of (isotropic-genesis polydomain) nematic balloons under tension. The second goal is to study actuation and shape-morphing in the presence of mechanical loads.…”

Section: Introductionmentioning

confidence: 88%

Actuation of cylindrical nematic elastomer balloons

Lee

Bhattacharya

2021

Journal of Applied Physics

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Nematic elastomers are programmable soft materials that display large, reversible and predictable deformation under an external stimulus such as a change in temperature or light. While much of the work in the field has focused on actuation from flat sheets, recent advances in 3D printing and other methods of directed synthesis have motivated the study of actuation of curved shells. Snap-through buckling has been a topic of particular interest. In this work, we present theoretical calculations to motivate another mode of actuation that combines programmable soft materials as well as instabilities associated with large deformation. Specifically, we analyze the deformation of a cylindrical shell of a patterned nematic elastomer under pressure, show that it can undergo an enormous change of volume with changing temperature and suggest its application as a pump with extremely high ejection fraction.

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“…Therefore, we hope that the general field of instabilities for LCE materials may serve as an inspiration for new devices or for systematic testing. For example, inflation instabilities were reported 124 for elongated nematic balloons. The inflation of cylindrical elastic balloons is often accompanied by different types of instabilities, such as bulging and necking.…”

Section: Instabilities In Liquid Crystal Elastomersmentioning

confidence: 99%

Instabilities in liquid crystal elastomers

Mihai

Goriely

2021

MRS Bulletin

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Stability is an important and fruitful avenue of research for liquid crystal elastomers. At constant temperature, upon stretching, the homogeneous state of a nematic body becomes unstable, and alternating shear stripes develop at very low stress. Moreover, these materials can experience classical mechanical effects, such as necking, void nucleation and cavitation, and inflation instability, which are inherited from their polymeric network. We investigate the following two problems: First, how do instabilities in nematic bodies change from those found in purely elastic solids? Second, how are these phenomena modified if the material constants fluctuate? To answer these questions, we present a systematic study of instabilities occurring in nematic liquid crystal elastomers, and examine the contribution of the nematic component and of fluctuating model parameters that follow probability laws. This combined analysis may lead to more realistic estimations of subsequent mechanical damage in nematic solid materials. Because of their complex material responses in the presence of external stimuli, liquid crystal elastomers have many potential applications in science, manufacturing, and medical research. The modeling of these materials requires a multiphysics approach, linking traditional continuum mechanics with liquid crystal theory, and has led to the discovery of intriguing mechanical effects. An important problem for both applications and our fundamental understanding of nematic elastomers is their instability under large strains, as this can be harnessed for actuation, sensing, or patterning. The goal is then to identify parameter values at which a bifurcation emerges, and how these values change with external stimuli, such as temperature or loads. However, constitutive parameters of real manufactured materials have an inherent variation that should also be taken into account, thus the need to quantify uncertainties in physical responses, which can be done by combining the classical field theories with stochastic methods that enable the propagation of uncertainties from input data to output quantities of interest. The present study demonstrates how to characterize instabilities found in nematic liquid crystal elastomers with probabilistic material parameters at the macroscopic scale, and paves the way for a systematic theoretical and experimental study of these fascinating materials.

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Anomalous inflation of a nematic balloon

Cited by 29 publications

References 16 publications

Fate of a bulge in an inflated hyperelastic tube: theory and experiment

Fate of a bulge in an inflated hyperelastic tube: theory and experiment

Actuation of cylindrical nematic elastomer balloons

Instabilities in liquid crystal elastomers

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