Fracture prediction is indispensable for polymers, like rubbers, which have a broad range of applications mainly due to their high extensibility. The phenomenon known as strain-induced crystallization further contributes to the fracture toughness of certain rubbers. In this study, a criterion based on internal bond energy, incorporating the effects of crystallization, is proposed to predict fracture

Curved features are ubiquitous on solid surfaces, but the effect of surface curvatures on growth of two-dimensional (2D) materials has not yet been established. Using a newly developed method based on the Metropolis algorithm and taking graphene as a prototype, we find that a curved feature on substrates can result in a variety of topological defects in 2D materials. As the feature's size increases

Two-dimensional (2D) materials as exemplified by graphene have received a bunch of attention for their outstanding properties and enormous application potential. Recently, a macroscopic graphene-based material was fabricated simply by stacking the few-layer graphene flakes. The resulting film, called SGA, exhibits unusual mechanical behavior, which implies the existence of tension-compression asymmetry

A geometrically nonlinear phase field theory accounting for dissipation, rate effects, nonlinear thermoelasticity, fracture, and other structural changes is constructed in the context of continuum thermodynamics. First, a general framework accommodating arbitrary strain energy potentials, inelastic deformation kinematics, and unlimited order parameters is formulated. Next, the framework is specialized

Wave propagation in granular materials is one of the most fundamental problems in mechanics and physics, with both scientific fascination and practical importance. Whether elastic waves in granular media are affected by particle morphology and, if yes, how they are affected remain open questions. Here we present a novel grain-scale model to address these fundamental questions. Efficient techniques

Multi-stable structures offer a unique set of mechanical properties, such as the ability to undergo large reversible deformations, the ability to provide mechanical protection and efficient shock absorption, and the ability to retain variety of geometrical configurations after loads have been removed. In addition, the study of lattice-based multi-stable structures is of relevance to a wide range of

Damage and fracture can be induced not only by mechanical loading but also due to chemical interactions within a solid. On one hand, species concentration may embrittle or toughen the material and on the other hand, the mechanical state adds additional driving force for diffusion. We propose a chemo-mechanically coupled cohesive fracture model with several novel features. It distinguishes the mode-dependent

Dielectric elastomers are a class of solid polymeric materials that are sufficiently soft to deform under the application of an electric field due to the interaction of quasi-static electric charges. Their potential to undergo large deformations renders them promising candidates for the design of energy harvesters, sensors and soft actuators. For their application however, the influence of additional

Interlocking composites have become increasingly popular in recent years. A key motivation is the impressive performance of natural interlocking protective structures. A large number of these structures – from human craniums to alligator armour – contain sutures; those are soft interfaces that join adjacent stiff plates with interdigitating protrusions. These interfaces have the potential to significantly

In recent years, the investigation of adhesion properties of thin films on brittle substrates is receiving more attention due to the spread of thin film applications (coatings, protective layers, conductive layers in microelectronics, etc.). However, a basic approach for adhesion measurements proposed by Hutchinson and Suo almost three decades ago is still widely used due to its easy applicability

Reaction-diffusion models have been widely used to elucidate pattern formation in developmental biology. More recently, they have also been applied in modeling cell fate patterning that mimics early-stage human development events utilizing geometrically confined pluripotent stem cells. However, the traditional reaction-diffusion equations could not satisfactorily explain the concentric ring distributions

Terrestrial snakes, aquatic snakes, and sandfish lizards are observed to adopt different configurations for locomotion, although they all employ the snake-like un-dulatory wriggling motion. Here we show that these differences may be dominated by the movement and energy efficiencies imposed by mechanical deformation and interaction with environments. Based on a slender soft beam model, a systematical

Hard-magnetic soft materials, which consist of soft matrix embedded with hard-magnetic particles, have attracted tremendous interests owing to their untethered control capability, rapid response, and flexible programmability. This work introduces a topology optimization framework to guide the rational design of hard-magnetic soft materials and structures with precisely programmable functionalities

Here we consider the possible bulk and shear moduli of planar polycrystals built from a single crystal in various orientations. Previous work gave a complete characterization for crystals with orthotropic symmetry. Specifically, bounds were derived separately on the effective bulk and shear moduli, thus confining the effective moduli to lie within a rectangle in the (bulk, shear) plane. It was established

High-mobility semiconductive ultrathin films of bismuth oxyselenide (Bi2O2Se) have attracted great interest due to their potential applications in advanced electronic and photoelectronic devices. Enthusiasm aside, future success of such applications hinges upon the fundamental understanding of two dimensional (2D) Bi2O2Se, which is far from mature. In particular, unlike many other 2D materials with

Theories describing the important role of small particles for strengthening of metals have evolved since the pioneering work of Orowan. Here, this problem is analysed by a strain gradient plasticity (SGP) theory. The structure of the governing equations on non-dimensional form reveals that the plastic strain in the matrix material is to zeroth order approximation constant for a sufficiently small particle

This paper presents a novel in-silico tool for the design of complex multilayer Dielectric Elastomers (DEs) characterised by recently introduced layer-by-layer reconfigurable electrode meso-architectures. Inspired by cutting-edge experimental work at Clarke Lab (Harvard) Hajiesmaili and Clarke (2019), this contribution introduces a novel approach underpinned by a diffuse interface treatment of the

A strain gradient void-driven ductile fracture model of single crystals is proposed and applied to simulate crack propagation in single and oligo-crystal specimens. The model is based on a thermodynamical framework for homogenized porous solids unifying and generalizing existing thermodynamical formulations. This porous single crystal ductile fracture model relies on a multi-surface representation

A multi-physics model is proposed to predict the changes in the constitutive behavior of cross-linked polymeric systems due to damages induced by deformation, oxidation, moisture, and temperature. Coupling the concept of network evolution, hydrolysis, and thermo-oxidation aging, we hypothesize that the synergized effects of deformation-induced damage, as well as different environmental factors such

Injectable bioelectronic devices provide programmable drug volume delivery control via flexible electrochemical pumps featuring scalable designs for localized drug delivery experiments involving small animals and future drug delivery in humans, especially for life saving medication. A model for the drug delivery time is established from the ideal gas law, finite-deformation theory of flexible membrane

Propagating cracks may deflect due to dynamic instability, running into pre-existing weak regions of heterogeneous media, or encountering variation in driving forces. The mechanical analysis of a kinked crack is of engineering significance for safety control and crack-network formation. Existing theories for kinked cracks relied on the perturbation method, as befit small kinks. The stress intensity

Sucrose is a commonly used energetic material simulant for β-HMX. However, its behavior under extreme loading conditions remains poorly understood. Pressure-Shear Plate Impact (PSPI) experiments have been conducted to provide an experimental foundation for developing a suitable constitutive model for sucrose. Experiments have been performed at two different nominal normal stress values, 3 and 9.5 GPa

Dry adhesives that rely on surface force mediated adhesion, such as van der Waals forces, are important in applications ranging from robotics to manufacturing. The maximum theoretical adhesion strength of a contact is achieved when the stress is uniformly distributed over the entire contact area as the full potential of all the bonds at the interface is realized in this scenario. Most dry adhesive

Stress concentration occurs at the crack tip of a notched sample when loaded. The crack tip region has been recognized of consisting of two regions: the inner (or end) region, which is also called the fracture process zone, and the surrounding outer region where inelastic deformation occurs. The size of these regions is strongly related to the fatigue threshold and the toughness of the material, and

Liquid crystal elastomers combine the hyperelasticity of elastomers with the multi-functionality of liquid crystals and have emerged as an important class of soft active materials. Monodomain liquid crystal elastomers under loading exhibit the soft elastic behavior due to the stress induced director rotation and the resulting spontaneous strain. Here, we numerically study their stress and strain concentration

During plastic deformation of crystalline materials, point defects such as vacancies and interstitials are generated by jogs on moving dislocations. A detailed model for jog formation and transport during plastic deformation was developed within the vector density-based continuum dislocation dynamics framework (Lin and El-Azab, 2020; Xia and El-Azab, 2015). As a part of this model, point defect generation

Universal deformations of an elastic solid are deformations that can be achieved for all possible strain–energy density functions and suitable boundary conditions. They play a central role in nonlinear elasticity and their classification has been mostly accomplished for isotropic solids following Ericksen’s seminal work. Here, we address the same problem for transversely isotropic, orthotropic, and

When subjected to some anti-plane shear mode III loading, segmentation of the crack front frequently occurs during propagation: even if the crack is initially planar, propagation produces facets/segments rotated toward the shear free direction. Here, we examine, both experimentally and theoretically, the effect of this microstructure on the effective macroscale brittle fracture toughness. Experiments

Frictional sliding is an intrinsically complex phenomenon, emerging from the interplay between driving forces, elasto-frictional instabilities, interfacial nonlinearity and dissipation, material inertia and bulk geometry. We show that homogeneous rate-and-state dependent frictional systems, driven at a prescribed boundary velocity — as opposed to a prescribed stress — in a range where the frictional

Fiber-reinforced soft composites with anisotropic mechanical properties exist widely in nature, forming complex shape-morphing structures during the growth or hydration processes. In this paper, we employ the 3D printing method, termed direct ink writing (DIW), to fabricate the hydrogel-fiber composites. It is found that the fiber distribution is controlled by printing parameters, such as printing

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

BN fiber coatings in SiC-SiC composites are vulnerable to oxidation and volatilization at elevated temperature in the presence of water vapor. These processes lead to coating recession in the composite interior with recession fronts starting from matrix cracks and proceeding axially along the fibers. In some operational domains, the main effect of recession is to de-couple the fibers from the matrix

Combining experimental and computational studies of nanocomposite interfaces is highly needed to gain insight into their performance. However, there are very few literature reports, combining well-controlled atomic force microscopy experiments with molecular dynamic simulations, which explore the role of polymer chemistry and assembly on interface adhesion and shear strength. In this work, we investigate

Fracture is a highly nonlinear problem, especially under a large deformation in cross-linked elastomers. Existing constitutive theories and fracture models fail to predict the fracture behavior of cross-linked elastomers because of the absence of the random polymer network structure. Meanwhile, few numerical methods can present the realistic fracture process of a polymer network. In this study, we

Epitaxial growth on a surface vicinal to a high-symmetry crystallographic plane occurs through the propagation of atomic steps, a process called step-flow growth. In some instances, the steps tend to form close groups (or bunches), a phenomenon termed step bunching, which corresponds to an instability of the equal-spacing step propagation. Over the last fifty years, various mechanisms have been proposed

The adhesive interactions between polymer nanofibers strongly influence the mechanical behavior of their networks in synthetic materials and biological systems. A treatment of the adhesive interactions at polymer contacts must take into account the viscoelastic behavior of the material in the contact region and the associated energy dissipation. This study focuses on the rate-dependent adhesion of

There has been increasing experimental evidence of non-affine elastic deformation mechanisms in biological soft tissues. These observations call for novel constitutive models which are able to describe the dominant underlying micro-structural kinematic aspects, in particular relative motion characteristics of different phases. This paper proposes a flexible and modular framework based on a micromorphic

The quasistatic approximation is a useful but questionable simplification for analyzing step instabilities during the growth/evaporation of vicinal surfaces. Using this approximation, we characterized in Part I of this work the effect on stability of different mechanisms and their interplay: elastic step-step interactions, the Schwoebel barrier, and the chemical coupling of the diffusion fields on

Geometrically frustrated elastic ribbons exhibit, in many cases, significant changes in configuration depending on the relation between their width and thickness. We show that the existence of such a transition, and the scaling at which it occurs, strongly depend on the system considered. Using an asymptotic approach, treating the width as a small parameter, we find the leading energy terms resulting

Mechanical metamaterials provide tailorable functionality based on a careful combination of base material and structural architecture. Truss-based metamaterials, e.g., exploit structural topology and beam geometry to achieve beneficial mechanical and physical properties from stiffness and wave dispersion to strength and toughness. While the focus to date has been primarily on static metamaterial properties

Anterior cruciate ligament (ACL) injury rates are rising, and there is little consensus about what puts someone at risk for an ACL injury. Finite element models provide an effective platform for systemically determining the effect of possible injury risk factors on ACL strain concentrations. However, the accuracy of a finite element model relies on the accuracy of the material models used in its construction

Certain eukaryotic cells are believed to sense and respond to vibrational stimuli that are too small even to be transduced by mechanosensitive ion channels. One possible mechanism of signal amplification and transduction is torsional and translational resonance of the nucleus, the stiffest and densest organelle in a eukaryotic cell. To explore this possibility, we developed a theoretical model that

The application of hydrogels has recently expanded markedly owning to the achievement of strong adhesion. In characterizing adhesion, a hydrogel is often subjected to 90-degree peel, during which the peel force increases, maximizes then drops to a plateau at steady state. The steady state peel force determines the adhesion toughness. The maximum peel force determines a debonding resistance that is

We present a theory for coupled deformation and liquid permeation in polymer gels, allowing for large strains and rotations in conjunction with sharp interfaces separating regions of high and low polymer volume fraction. The theory is applied to pressure-driven liquid flow through a gel-filled rectangular channel, with the aim of investigating how the elastic and osmotic properties of the gel influence

This paper develops a method for physics-based augmentation of the Helmholtz free energy density functionals, used in coupled crystal plasticity phase-field finite element (CP-PF FE) models of fracture in crystalline metallic materials. Specifically, the defect and crack surface energy components are enhanced with terms that mechanistically account for the presence of atomic-scale, crack-tip nucleated

The mechanical Pyrochlore lattice was experimentally tested to demonstrate an intrinsically polar behavior of the material, which is soft on one side and hard on the opposite side (Bilal et al., 2017). The topological polarization in Pyrochlore lattices begs for developing a new effective medium theory because conventional Cauchy effective theories cannot predict the polarization phenomenon. In this

A key cause of chemo-mechanical degradation in battery electrodes is that they undergo abrupt phase transformation during the charging/discharging cycle. This phase transformation is accompanied by lattice misfit strains that nucleate microcracks, induce fracture and, in extreme cases, amorphize the intercalation electrode. In this work, we propose a strategy to prevent the chemo-mechanical degradation

We extend the model-free data-driven paradigm for rate-independent fracture mechanics proposed in Carrara et al. (2020), to rate-dependent fracture and sub-critical fatigue. The problem is formulated by combining the balance governing equations stemming from variational principles with a set of data points that encodes the fracture constitutive behavior of the material. The solution is found as the

Fatigue crack nucleation at annealing twin boundaries (TBs) within polycrystal nickel-based superalloy René 88DT is investigated with a microstructure-sensitive crystal plasticity (CP) model, digital image correlation strain measurements and experimental SEM crack nucleation observations. Strong slip localizations at TBs were experimentally observed and predicted by the CP model, which also showed

A constitutive model for elastic–plastic materials is developed using scalar, conjugate, stress–strain, base pairs in a finite deformation setting. These conjugate base pairs arise from an alternative QR decomposition of the deformation gradient that decomposes its matrix into an orthogonal rotation and an upper-triangular matrix, called the Laplace stretch. This decomposition is particularly useful

Elastic waves scattered by randomly rough surfaces in solid media play an important role across research topics including ultrasonic wave detection and imaging, seismic wave exploration and phonon boundary interaction. Previous attention has focused upon the mean/expected scattering intensity for both compressional (P) and shear (S) waves. In this article, the variance or the standard deviation (sd)

Metamaterials are artificial structures that can manipulate and control sound waves in ways not possible with conventional materials. While much effort has been undertaken to widen the bandgaps produced by these materials through design of heterogeneities within unit cells, comparatively little work has considered the effect of engineering heterogeneities at the structural scale by combining different

Exact solutions are derived for the small-strain, in-plane, elasto-plastic response of a hexagonal honeycomb using slender beam theory; incompressibility of the honeycomb is enforced by filling its voids with an incompressible, inviscid fluid. The honeycomb has sides of equal length, but its inclined struts subtend an angle that can deviate from 120° with respect to the vertical side walls. The relative

A fully coupled poroelastic solution for spherical indentation into a half space with an impermeable surface when the indenter is subjected to step displacement loading is presented. The solution is obtained within the framework of Biot’s theory using the McNamee–Gibson displacement function method. Mathematical difficulties associated with solving poroelastic contact problems are overcome by the use

Reversibility is of paramount importance in the correct representation of surface peeling in various physical settings, ranging from motility in nature, to gripping devices in robotic applications, and even to sliding of tectonic plates. Modeling the detachment–reattachment sequence, known as stick–slip, imposes several challenges in a continuum framework. Here we exploit customized reversible cohesive