Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session G09: Friction, Fracture, and Adhesion in Soft Materials IFocus
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Sponsoring Units: DSOFT Chair: Xin Yong, Binghamton University Room: Room 132 |
Tuesday, March 7, 2023 11:30AM - 12:06PM |
G09.00001: Toughening of brittle materials through crack tip complexity Invited Speaker: John M Kolinski Brittle fracture is characterized by a direct relationship between the strain energy that drives the crack on the one hand, and the fracture energy on the other hand, in the form of energy balance. This leaves little room to augment toughness without modifying the material by introducing inclusions, as is common practice for composite solids. However, this raises an important question: can anything be done to enhance the toughness of a brittle solid without modifying the material? We suggest that any means by which the crack front can be made more complex may enhance effective fracture toughness, in a manner consistent with energy balance. Crack tip complexity emerges when a crack breaks its planar symmetry, and the crack tip loading conditions become fully 3D. As a consequence of the geometric complexity of the crack tip, more fracture surface is generated when the crack advances, requiring additional strain energy for the crack to progress. Here, we study the toughness enhancement of a brittle solid through crack tip complexity, realized in an otherwise `ideally brittle' hydrogel. Using optical sectioning microscopy methods, we can directly measure the crack tip complexity, and simultaneously measure the far-field, effective fracture energy using the crack tip opening displacement (CTOD). We find that the effective fracture energy increases with the length of the 3D space-curve traced out by the crack tip. This result directly demonstrates an effective toughness enhancement of neat, brittle solids based entirely on crack tip complexity. The 3D loading conditions realized at the tip of such complex cracks raise significant challenges for the physics and engineering science community centered on crack tip stability. Our detailed in-situ measurements might be used to motivate the development of a theory for 3D fracture that could allow for facile interpretation of effective fracture energy of brittle solids with complex crack tips when the crack front geometry is known. |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G09.00002: Understanding aortic dissection through phase field fracture modeling in curved geometries Nhung Nguyen, Willa Li, Enrique Cerda, Luka Pocivavsek Aortic dissection is a fracture problem where a tear in the intima propagates helically along the aorta’s axial direction. This leads to delamination between layers of the aortic wall and the creation of the false lumen where blood can enter and cause potential problems like rupture. The mechanism for aortic dissection is unclear due to the complex coupling of the loading, the curved geometry and the anisotropy of the aortic wall. In this work, we implement a phase field fracture modeling with a fiber-reinforced material model for the aortic wall using ABAQUS material subroutine VUMAT. The model is tested through benchmark fracture problems. It is then used to study how crack propagates in idealized curved geometries such as along a bended cylinder with varying degrees of Gaussian curvature. This provides insight on how curvature and the initial tear’s location affect the crack path, which is critical to understand aortic dissection propagation. Through modeling the aortic wall as a multi-layer composite, the model will also help to understand how the delamination occurs along layers of the aortic wall. Furthermore, our implementation opens the way to integrate solid-fluid interactions through Abaqus and Xflow to study how the false lumen is developed in the dissection process. |
Tuesday, March 7, 2023 12:18PM - 12:30PM |
G09.00003: Predicting Crack Trajectory Using "Elastic Charges" Oran Szachter, Emmanuel Siéfert, Eran Sharon, Mokhtar Adda-Bedia, Michael Moshe Predicting the trajectory of a crack in residually stressed solids is a formidable challenge in the field of solid mechanics. A central difficulty arises from the dynamic nature of the boundary conditions due to crack evolution. Here we introduce a method that avoids this difficulty by describing cracks as distributed induced "elastic charges." We show that quasi-static crack evolution is equivalent to a propagating non-topological dislocation. We implement our method to predict the trajectory of a crack in the vicinity of a topological defect that acts as an internal source of stress. Our theory is supported by a good agreement between the predicted trajectories and the experimental measurements of cracks moving in dislocated elastic media. |
Tuesday, March 7, 2023 12:30PM - 12:42PM |
G09.00004: Elucidating nature of elastomeric fracture by local characterization Shi-Qing Wang, Zehao Fan This work studies the effect of sample thickness on fracture behavior of polybutadiene rubber (BR). Single edge notch (SEN) test pieces with three varying thicknesses, 0.6 mm, 1.3 mm, and 5.2 mm and involving four cut sizes from 0.8 to 8.3 mm. By making in situ spatially resolved photoelasticity (e.g., birefringence), we show how strain field builds up around crack tip all the way to the onset of fracture. We confirm a previous study1 that upon approach cut tip stress ceases to build up and reveal a stress plateau zone (SSZ) of a size independent of load. With increasing thickness, fracture toughness (Gc or Kc) remains the same, corresponding to the critical tip stress at fracture sigma_tip(F) (equal to the inherent strength) decreasing and SSZ size increasing as thickness increases. |
Tuesday, March 7, 2023 12:42PM - 12:54PM |
G09.00005: Controlled Radical Polymerizations as a Tool to Tailor the Architecture and Fracture Properties of Polymer Networks Gabriel E Sanoja, Aaliyah Z Dookhith, Apratim R Chowdhury, Sutton B Landers-Carlyon Soft materials find widespread use as elastomers and hydrogels because they can sustain large reversible deformations. These materials are constituted of polymer networks that rely on molecular friction to dissipate strain energy in the vicinity of cracks, and have an inherent trade-off between mechanical properties like stiffness and toughness. A strategy to circumvent this trade-off is to interpenetrate a stiff and highly crosslinked sacrificial network into a soft and extensible matrix, leading to a family of materials referred to as multiple-networks that dissipate a notable amount of energy by chain scission. Here, we investigated the role of sacrificial network architecture (i.e., homogeneity) on energy dissipation and fracture toughness of multiple-networks. The key result is that more homogeneous sacrificial networks, as enabled by controlled radical copolymerizations like RAFT, afford tougher multiple-networks than analogues synthesized by free radical copolymerization. Such control over the sacrificial network architecture and fracture properties of multiple-networks is essential for attaining stiffness and toughness in conditions where molecular friction is negligible like high temperatures or high water concentrations. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G09.00006: Energy dissipation after the fracture of end-linked polymer networks using molecular simulations Han Zhang, Ziyu Ye, Robert A Riggleman The fracture of end-linked polymer networks and gels strongly affects the performance of these versatile and widely used materials, and a molecular-level understanding of the fracture energy is important to the design of new materials. The Lake-Thomas theory serves as a framework to understand and quantify the energy dissipation due to the chain scission in these materials based on an idealized picture of fracture in networks. Recent extensions of the Lake-Thomas theory have incorporated the effect of topological defects, such as loop defects, and in some examples enabled accurate prediction of the fracture. In this talk, I will describe how we use coarse-grained molecular dynamics simulations and network analysis techniques to provide a molecular view of the energy dissipated during chain scission in polymer networks. In addition to the energy of the broken strand, we also consider the amount of energy released by the networks connected to the broken chain and other sources of energy dissipation due to the fracture process. Our results can be used to further refine the description of the processes at play during the failure of polymer networks. |
Tuesday, March 7, 2023 1:06PM - 1:18PM |
G09.00007: Tailoring network architecture and fracture properties of polyether networks using organo-aluminum catalysts Aaliyah Z Dookhith, Nathaniel A Lynd, Gabriel E Sanoja Polyethers are ubiquitous in engineering and biomedical applications with their oxygen rich backbone allowing them to interact with a variety of polar small molecules such as ions, gases, and pharmaceuticals. When crosslinked at the molecular scale, these materials can also sustain large reversible deformations, leading to an interesting combination of functional and mechanical properties. We synthesized two families of polyether networks by organoaluminum catalyzed ring-opening copolymerization of ethyl glycidyl ether monomer and 1,4-butanediol diglycidyl ether crosslinker, and explored the relationship between network architecture and fracture properties. The key result is that living copolymerizations (i.e. more controlled), as enabled by a chelate of triethylaluminum with dimethylaminoethanol, afford access to a critical cross-link density, νx ≈ 3 x 1025 chains/m3, and loss tangent, tan(δ) ≈ 0.09, at which fracture is dominated by chain scission rather than friction. Such control over the fracture resistance of polyether networks unveils the potential of living copolymerizations to design the functional and mechanical properties of soft materials. |
Tuesday, March 7, 2023 1:18PM - 1:30PM |
G09.00008: Fracture of elastomeric materials across length-scales: experiments and nonlocal continuum modeling Jaehee Lee, Jeongun Lee, Seunghyeon Lee, Hansohl Cho In this work, we investigate the fracture behavior of elastomeric materials across a wide range of length-scales using experiments and nonlocal continuum modeling. Specifically, we conducted precisely controlled desktop-scale mode-I tension tests for notched specimens made of photo-curable elastomers with various notch lengths. We clearly observed the size-dependent fracture behavior in the material, i.e., the macroscopic rupture stretch increases significantly as the notch length (or the specimen size) decreases. We also make use of a nonlocal continuum mechanics-based phase-field approach to model the fracture process in the materials subjected to large stretch; the nonlocal gradient-damage theory was numerically implemented for use in a finite element solver for coupled, nonlinear boundary value problems for fracture in elastomers. Our numerical simulation was found to be able to capture the main features of the size-dependent fracture in the materials revealed in experiments. Furthermore, using both experiments and gradient-damage theory-based numerical simulations, we address the transition from the flaw-sensitive to the flaw-insensitive fracture behavior strongly associated with the nonlocal nature of underlying physics in the fracture processes in elastomers. |
Tuesday, March 7, 2023 1:30PM - 1:42PM |
G09.00009: Crack patterns in drying binary-mixture suspensions Xiaolei Ma, Amir Pahlavan Gaining control over the drying of particulate suspensions is important in a wide range of applications including coating and printing of electronic circuits. While most of these applications rely on multicomponent mixture of solvents to achieve their desired functionality, our current understanding of crack patterns and their evolution is limited to single-solvent suspensions. Here we report on our observations of drying suspensions of colloidal particles dispersed in binary liquids. We discuss how differential evaporation of the two liquids and the resulting surface tension gradients can influence the spatiotemporal evolution of the crack morphologies. |
Tuesday, March 7, 2023 1:42PM - 1:54PM |
G09.00010: Competing and global fractures in 2-D compressed crystalline bubble arrays. Pablo E Illing, Jean-Christophe Ono-dit-Biot, Kari Dalnoki-Veress, Eric R Weeks
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Tuesday, March 7, 2023 1:54PM - 2:06PM |
G09.00011: Granular failure from micro- to meso- to macro-scale Karen E Daniels, Nakul Deshpande, Farnaz Fazelpour, Jack Featherstone, Silke Henkes, Charlie E Mundorf, J. M Schwarz When a granular material suddenly fails at the macroscopic scale, the rupture begins as some microscopic frictional/energetic failure criterion is surpassed, which locally mobilizes particles and results in macroscopic structural changes. I will present a series of experiments which start at this smallest scale and proceed through the force chain scale to elucidate how failure nucleates. Our experiments are performed on photoelastic particles which allow us to measure both the dynamics (normal and tangential forces at each contact) and kinematics (particle trajectories), and thereby quantify which failure criteria are at work under various conditions. Importantly, rigidity is a mesoscale property and it is therefore necessary to consider the network of interactions, which we achieve through the use of the Pebble Game. |
Tuesday, March 7, 2023 2:06PM - 2:18PM |
G09.00012: The effect of surface features on friction forces in granular media Calvin Riiska, Miller Vu, Jennifer Rieser Biological surfaces are covered with diverse features and textures whose functions are often unknown. In some cases, however, progress has been made; for instance, structures that serve as interface with underlying substrates, e.g., setae on gecko feet and microscopic spikes found on snake belly skins, are likely important for movement. Here, inspired by textures present on snake bellies, we investigate how textures affect frictional forces. Using 3D printing, we created and systematically varied texture feature sizes (from tens of microns to one centimeter), aspect ratios, and orientations printed on square plates that are then dragged (at constant speed) through granular material as a function of angle of attack. We find that textured surfaces do affect the magnitude and direction-dependence of frictional drag forces, with differences depend on the details and orientation of the textured pattern. Our results provide a starting point for understanding how differing animal surface textures may alter locomotive capabilities in order to adapt to a changing environment. |
Tuesday, March 7, 2023 2:18PM - 2:30PM |
G09.00013: Instabilities in frictional sliding: From Schallamach waves to locomoting invertebrates Koushik Viswanathan Intermittent motion, called stick-slip, is a friction instability that commonly occurs during relative sliding of two elastic solids. In adhesive polymer contacts, where elasticity and interface adhesion are strongly coupled, stick-slip arises due to the propagation of slow detachment waves at the interface. Here we analyze two distinct detachment waves moving parallel (Schallamach wave) and antiparallel (separation wave) to applied remote sliding. Both waves cause slip in the same direction, travel at speeds much lesser than any elastic wave speed, and are therefore describable using the same perturbative elastodynamic framework with identical boundary conditions. Our calculations reveal a close correspondence between moving detachment waves and bimaterial interface cracks, including the nature of the singularity and the functional forms of the stresses. Based on this correspondence, and coupled with a fracture analogy for dynamic friction, we develop a phase diagram showing domains of possible occurrence of stick-slip via detachment waves vis-á-vis steady interface sliding. We also describe an Ising-like lattice analogue of this system, discuss the nature of the associated transition from stick to slip at the interface, and establish similarities with other phenomena in geophysics and invertebrate locomotion. We close with some comments about the possibility of dynamic interface waves, propagating at speeds comparable to elastic wave speeds in the two slid solids. |
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