Pub Date : 2025-12-02DOI: 10.1016/j.eml.2025.102431
Christine Heera Ahn, Zheqi Chen, Xianyang Bao, Zhigang Suo
In a brittle polymer glass, a fracture property increases with the length of polymer chains and then plateaus. Here, we use poly(methyl methacrylate) to study such transitions in several fracture properties. We measure strength using samples without precut crack, and measure toughness and fatigue threshold using samples with precut crack. The three properties plateau at different chain lengths. These transitions arise from a change in fracture mechanism—from chain pullout to chain scission. The chain length for a fracture property to plateau is understood using a shear-lag model. The plateau length is set by the balance of the strengths of bonds of two types: the covalent bonds along the chains, which resists scission, and the noncovalent bonds between the chains, which resist pullout. For each of the three fracture properties, we discuss the chain length for the property to plateau, as well as the value of the plateau.
{"title":"How does chain length affect fracture of a brittle polymer glass?","authors":"Christine Heera Ahn, Zheqi Chen, Xianyang Bao, Zhigang Suo","doi":"10.1016/j.eml.2025.102431","DOIUrl":"10.1016/j.eml.2025.102431","url":null,"abstract":"<div><div>In a brittle polymer glass, a fracture property increases with the length of polymer chains and then plateaus. Here, we use poly(methyl methacrylate) to study such transitions in several fracture properties. We measure strength using samples without precut crack, and measure toughness and fatigue threshold using samples with precut crack. The three properties plateau at different chain lengths. These transitions arise from a change in fracture mechanism—from chain pullout to chain scission. The chain length for a fracture property to plateau is understood using a shear-lag model. The plateau length is set by the balance of the strengths of bonds of two types: the covalent bonds along the chains, which resists scission, and the noncovalent bonds between the chains, which resist pullout. For each of the three fracture properties, we discuss the chain length for the property to plateau, as well as the value of the plateau.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102431"},"PeriodicalIF":4.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01DOI: 10.1016/j.eml.2025.102430
Dezhong Tong , Andrew Choi , Jiaqi Wang , Weicheng Huang , Zexiong Chen , Jiahao Li , Xiaonan Huang , Mingchao Liu , Huajian Gao , K. Jimmy Hsia
Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses – bending, twisting, buckling, wrinkling, and self-contact – that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry-first, structure-preserving paradigm for modeling such behaviors. Unlike finite element or mass–spring methods, DDG discretizes geometry rather than governing equations, allowing curvature, twist, and strain to be defined directly on meshes. This approach yields robust large-deformation dynamics, accurate handling of contact, and differentiability essential for inverse design and learning-based control. This review consolidates the rapidly expanding landscape of DDG models across 1D and 2D systems, including discrete elastic rods, ribbons, plates, and shells, as well as multiphysics extensions to contact, magnetic actuation, and fluid–structure interaction. We synthesize applications spanning mechanics of nonlinear instabilities, biological morphogenesis, functional structures and devices, and robotics from manipulation to soft machines. Compared with established approaches, DDG offers a unique balance of geometric fidelity, computational efficiency, and algorithmic differentiability, bridging continuum rigor with real-time, contact-rich performance. We conclude by outlining opportunities for multiphysics coupling, hybrid physics–data pipelines, and scalable GPU-accelerated solvers, and by emphasizing DDG’s role in enabling digital twins, sim-to-real transfer, and intelligent design of next-generation flexible systems.
{"title":"Discrete differential geometry for simulating nonlinear behaviors of flexible systems: A survey","authors":"Dezhong Tong , Andrew Choi , Jiaqi Wang , Weicheng Huang , Zexiong Chen , Jiahao Li , Xiaonan Huang , Mingchao Liu , Huajian Gao , K. Jimmy Hsia","doi":"10.1016/j.eml.2025.102430","DOIUrl":"10.1016/j.eml.2025.102430","url":null,"abstract":"<div><div>Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses – bending, twisting, buckling, wrinkling, and self-contact – that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry-first, structure-preserving paradigm for modeling such behaviors. Unlike finite element or mass–spring methods, DDG discretizes geometry rather than governing equations, allowing curvature, twist, and strain to be defined directly on meshes. This approach yields robust large-deformation dynamics, accurate handling of contact, and differentiability essential for inverse design and learning-based control. This review consolidates the rapidly expanding landscape of DDG models across 1D and 2D systems, including discrete elastic rods, ribbons, plates, and shells, as well as multiphysics extensions to contact, magnetic actuation, and fluid–structure interaction. We synthesize applications spanning mechanics of nonlinear instabilities, biological morphogenesis, functional structures and devices, and robotics from manipulation to soft machines. Compared with established approaches, DDG offers a unique balance of geometric fidelity, computational efficiency, and algorithmic differentiability, bridging continuum rigor with real-time, contact-rich performance. We conclude by outlining opportunities for multiphysics coupling, hybrid physics–data pipelines, and scalable GPU-accelerated solvers, and by emphasizing DDG’s role in enabling digital twins, sim-to-real transfer, and intelligent design of next-generation flexible systems.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102430"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1016/j.eml.2025.102429
Dichao Ning, Zihan Zhang, Chenyu Jin, Qian Shi
Rubber is widely applied due to its high elasticity and durability, but traditional crosslinked networks are non-recyclable. The incorporation of dynamic covalent bonds endows vitrimers with recyclability and self-healing ability. However, the regulatory effect of curing kinetics and chemical ratio on dynamic covalent bonds has not been systematically studied, and such regulation is crucial for designing high-performance rubber vitrimers. In this work, rubber vitrimers with hybrid network were synthesized by using epoxy monomers and curing agent containing disulfide bonds. By varying the chemical ratio of soft segments (PEG) and hard segments (BPDG or DGEBA), and tuning curing time, we characterized their dynamic performance, tensile properties and fracture toughness. Furthermore, kinetic equation was incorporated into and used to extend the Lake–Thomas model, enabling quantitative description and prediction of fracture energy. The results demonstrate that increased curing degree and disulfide bond proportion enhance the fracture toughness and fracture strain of the rubber polymer, but slightly reduce its strength and modulus. Moreover, the introduction of dynamic covalent bonds favors both fracture toughness and dynamic performance. This work provides theoretical guidance and processing strategies for the design of high-performance rubbers.
{"title":"The role of dynamic covalent bonds on mechanical properties of rubber vitrimer with hybrid networks","authors":"Dichao Ning, Zihan Zhang, Chenyu Jin, Qian Shi","doi":"10.1016/j.eml.2025.102429","DOIUrl":"10.1016/j.eml.2025.102429","url":null,"abstract":"<div><div>Rubber is widely applied due to its high elasticity and durability, but traditional crosslinked networks are non-recyclable. The incorporation of dynamic covalent bonds endows vitrimers with recyclability and self-healing ability. However, the regulatory effect of curing kinetics and chemical ratio on dynamic covalent bonds has not been systematically studied, and such regulation is crucial for designing high-performance rubber vitrimers. In this work, rubber vitrimers with hybrid network were synthesized by using epoxy monomers and curing agent containing disulfide bonds. By varying the chemical ratio of soft segments (PEG) and hard segments (BPDG or DGEBA), and tuning curing time, we characterized their dynamic performance, tensile properties and fracture toughness. Furthermore, kinetic equation was incorporated into and used to extend the Lake–Thomas model, enabling quantitative description and prediction of fracture energy. The results demonstrate that increased curing degree and disulfide bond proportion enhance the fracture toughness and fracture strain of the rubber polymer, but slightly reduce its strength and modulus. Moreover, the introduction of dynamic covalent bonds favors both fracture toughness and dynamic performance. This work provides theoretical guidance and processing strategies for the design of high-performance rubbers.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102429"},"PeriodicalIF":4.5,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1016/j.eml.2025.102426
Yucheng Huo , Kexin Guo , Massimo Paradiso , K. Jimmy Hsia
Collective behaviors in cellular systems are regulated not only by biochemical signaling pathways but also by intercellular mechanical forces, whose quantification in contractile monolayers remains poorly understood. Here, by integrating traction force microscopy and numerical simulations, we reconstruct the stress distribution in C2C12 myoblast monolayers to reveal the roles of local mechanical forces in determining the collective cellular structures. We find that contractile monolayers exhibit positive maximum and negative minimum principal stresses, reflecting the intrinsic anisotropy of active tension. Distinct stress patterns emerge around topological defects, coinciding with singularities in cell alignment, density, and morphology, indicating a strong coupling between mechanical forces and structural organization. Moreover, tensile stresses are preferentially transmitted along the cell elongation axis and compressive stresses transversely, demonstrating that local stress guides cell arrangement. This mechanical guidance appears to be universal among contractile systems, as observed also in bone marrow–derived mesenchymal stem cells. Together, our work establishes a quantitative framework for characterizing mechanical anisotropy in active cellular monolayers and reveals a general principle of force–structure coupling, providing a physical basis for understanding how mechanics governs myogenesis, morphogenesis, and collective organization in contractile cellular systems.
{"title":"Stress distribution in contractile cell monolayers","authors":"Yucheng Huo , Kexin Guo , Massimo Paradiso , K. Jimmy Hsia","doi":"10.1016/j.eml.2025.102426","DOIUrl":"10.1016/j.eml.2025.102426","url":null,"abstract":"<div><div>Collective behaviors in cellular systems are regulated not only by biochemical signaling pathways but also by intercellular mechanical forces, whose quantification in contractile monolayers remains poorly understood. Here, by integrating traction force microscopy and numerical simulations, we reconstruct the stress distribution in C2C12 myoblast monolayers to reveal the roles of local mechanical forces in determining the collective cellular structures. We find that contractile monolayers exhibit positive maximum and negative minimum principal stresses, reflecting the intrinsic anisotropy of active tension. Distinct stress patterns emerge around topological defects, coinciding with singularities in cell alignment, density, and morphology, indicating a strong coupling between mechanical forces and structural organization. Moreover, tensile stresses are preferentially transmitted along the cell elongation axis and compressive stresses transversely, demonstrating that local stress guides cell arrangement. This mechanical guidance appears to be universal among contractile systems, as observed also in bone marrow–derived mesenchymal stem cells. Together, our work establishes a quantitative framework for characterizing mechanical anisotropy in active cellular monolayers and reveals a general principle of force–structure coupling, providing a physical basis for understanding how mechanics governs myogenesis, morphogenesis, and collective organization in contractile cellular systems.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102426"},"PeriodicalIF":4.5,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-27DOI: 10.1016/j.eml.2025.102423
Cosima du Pasquier , Sehui Jeong , Pan Liu , Susan Williams , Nour Mnejja , Allison M. Okamura , Skylar Tibbits , Tian Chen
This work presents a multi-level modeling and design framework for weft knitted fabrics, beginning with a volumetric finite element analysis capturing their mechanical behavior from fundamental principles. Incorporating yarn-level data, it accurately predicts stress–strain responses, reducing the need for extensive physical testing. A simplified strain energy approach homogenizes the results into three key variables, enabling rapid, accurate predictions in minutes. After validation against experiments, our framework can simulate new knit fabrics without additional tests. In real-world scenarios, fabrics often feature variations in yarn materials or patterns. The framework extends to heterogeneous fabrics, showing that transitions between distinct regions can be captured using simple mechanical analogies: springs in series and parallel. This allows heterogeneous textiles to be treated as idealized patchworks of homogeneous pieces, preserving predictive accuracy. The method is demonstrated by designing and producing a compression sleeve with uniform pressure, illustrating how the framework supports development of knits tailored to specific assistance levels and anatomical features. By combining volumetric finite element analysis, simplified model through homogenization, and controlled material transitions, this approach provides a scalable, high-fidelity path toward next-generation weft knitted fabric design.
{"title":"Multi-level mechanical modeling and computational design framework for weft knitted fabrics","authors":"Cosima du Pasquier , Sehui Jeong , Pan Liu , Susan Williams , Nour Mnejja , Allison M. Okamura , Skylar Tibbits , Tian Chen","doi":"10.1016/j.eml.2025.102423","DOIUrl":"10.1016/j.eml.2025.102423","url":null,"abstract":"<div><div>This work presents a multi-level modeling and design framework for weft knitted fabrics, beginning with a volumetric finite element analysis capturing their mechanical behavior from fundamental principles. Incorporating yarn-level data, it accurately predicts stress–strain responses, reducing the need for extensive physical testing. A simplified strain energy approach homogenizes the results into three key variables, enabling rapid, accurate predictions in minutes. After validation against experiments, our framework can simulate new knit fabrics without additional tests. In real-world scenarios, fabrics often feature variations in yarn materials or patterns. The framework extends to heterogeneous fabrics, showing that transitions between distinct regions can be captured using simple mechanical analogies: springs in series and parallel. This allows heterogeneous textiles to be treated as idealized patchworks of homogeneous pieces, preserving predictive accuracy. The method is demonstrated by designing and producing a compression sleeve with uniform pressure, illustrating how the framework supports development of knits tailored to specific assistance levels and anatomical features. By combining volumetric finite element analysis, simplified model through homogenization, and controlled material transitions, this approach provides a scalable, high-fidelity path toward next-generation weft knitted fabric design.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102423"},"PeriodicalIF":4.5,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.eml.2025.102427
Xiao Hu , Haiping Wu , Qiwei Zhang , Hongbin Fang
Multi-stability, a hallmark of architected materials, has rarely been associated with Yoshimura origami—a classical pattern long regarded as mono-stable. In this study, we report the first experimental observation of peculiar multi-stability in Yoshimura structures and investigate both its evolution and regulation. By systematically varying the diagonal angle of the crease pattern, we reveal that small angles (≤30°) yield smooth, mono-stable force–displacement responses, whereas slightly larger angles (>30°) induce geometric incompatibility, facet bending, and successive snapping events. In particular, pronounced multi-stability emerges in structures with larger diagonal angles (34°), where multiple stable equilibria and negative stiffness phenomena are observed. To regulate these snapping, we introduce a crease-design strategy based on the PALEO cutting pattern, and experimentally establish quantitative relationships between crease stiffness and geometric design parameters. By tailoring crease stiffness across different sections of a Yoshimura prototype, all six possible snapping sequences in a three-section structure are successfully realized under compression. These results establish Yoshimura origami as a new member of the multi-stable origami family and introduce a systematic framework for regulating its snapping behavior, offering new opportunities for adaptive structures, mechanical computing, and programmable metamaterials.
{"title":"Peculiar multi-stability observed in Yoshimura origami structures: Evolution and regulation of snapping sequence","authors":"Xiao Hu , Haiping Wu , Qiwei Zhang , Hongbin Fang","doi":"10.1016/j.eml.2025.102427","DOIUrl":"10.1016/j.eml.2025.102427","url":null,"abstract":"<div><div>Multi-stability, a hallmark of architected materials, has rarely been associated with Yoshimura origami—a classical pattern long regarded as mono-stable. In this study, we report the first experimental observation of peculiar multi-stability in Yoshimura structures and investigate both its evolution and regulation. By systematically varying the diagonal angle of the crease pattern, we reveal that small angles (≤30°) yield smooth, mono-stable force–displacement responses, whereas slightly larger angles (>30°) induce geometric incompatibility, facet bending, and successive snapping events. In particular, pronounced multi-stability emerges in structures with larger diagonal angles (34°), where multiple stable equilibria and negative stiffness phenomena are observed. To regulate these snapping, we introduce a crease-design strategy based on the PALEO cutting pattern, and experimentally establish quantitative relationships between crease stiffness and geometric design parameters. By tailoring crease stiffness across different sections of a Yoshimura prototype, all six possible snapping sequences in a three-section structure are successfully realized under compression. These results establish Yoshimura origami as a new member of the multi-stable origami family and introduce a systematic framework for regulating its snapping behavior, offering new opportunities for adaptive structures, mechanical computing, and programmable metamaterials.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102427"},"PeriodicalIF":4.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-23DOI: 10.1016/j.eml.2025.102425
Ram Hemanth Yeerella , Shengqiang Cai
Architected materials are increasingly used in applications where large deformations are unavoidable. In the small-deformation regime, such periodic designs can be modeled as continuum elastic solids with effective elastic material properties, allowing Linear Elastic Fracture Mechanics (LEFM) to describe and predict their fracture behavior. But when such structures are pushed into large-strain conditions, often the critical design scenario—can we achieve a similar simplification to model them as continuum soft solids? In the current study, using finite element simulations of hexagonal honeycombs, we find that the crack tip stress and deformation fields are uniquely determined by the energy release rate (G), in Mode I loading. At high stretches, the stress singularity scaling relationship shifts from that predicted by LEFM to one characteristic of nonlinear hyperelastic solids. We further show that the driving force for fracture can be predicted by treating these lattices as hyperelastic continuum solids, provided the strain energy density of the uncracked lattice is known. These findings provide a pathway for a simple continuum-based framework to predict failure in a wide range of deformable architected material designs.
{"title":"Fracture in hexagonal honeycomb lattices undergoing large deformation","authors":"Ram Hemanth Yeerella , Shengqiang Cai","doi":"10.1016/j.eml.2025.102425","DOIUrl":"10.1016/j.eml.2025.102425","url":null,"abstract":"<div><div>Architected materials are increasingly used in applications where large deformations are unavoidable. In the small-deformation regime, such periodic designs can be modeled as continuum elastic solids with effective elastic material properties, allowing Linear Elastic Fracture Mechanics (LEFM) to describe and predict their fracture behavior. But when such structures are pushed into large-strain conditions, often the critical design scenario—can we achieve a similar simplification to model them as continuum soft solids? In the current study, using finite element simulations of hexagonal honeycombs, we find that the crack tip stress and deformation fields are uniquely determined by the energy release rate (<em>G</em>), in Mode I loading. At high stretches, the stress singularity scaling relationship shifts from that predicted by LEFM to one characteristic of nonlinear hyperelastic solids. We further show that the driving force for fracture can be predicted by treating these lattices as hyperelastic continuum solids, provided the strain energy density of the uncracked lattice is known. These findings provide a pathway for a simple continuum-based framework to predict failure in a wide range of deformable architected material designs.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"82 ","pages":"Article 102425"},"PeriodicalIF":4.5,"publicationDate":"2025-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-18DOI: 10.1016/j.eml.2025.102422
Kenya Hazell , Anesia Auguste , Andrew Gillman , Lawrence F. Drummy
Traditionally, plastic deformation and the micromechanics of thin polymer films have been evaluated under uniaxial or linear strain. As the use of thin film polymeric materials continues to expand into applications in flexible electronics, gas separation, energy storage and sensing, more work needs to be done to understand how these materials behave under realistic conditions. Concurrently, certain mechanical metamaterials offer the ability to investigate non-linear and multi-axis micromechanics through lattice structures with designed spatially-varying complex strain fields. While previous studies using a support structure have been performed to study polymer crazing in thin films under biaxial or shear conditions, their behavior under complex strain has not been reported. This work offers a new method in which complex strain analysis in polymer films can be performed using an auxetic support lattice with a designed Poisson’s ratio (v) that is defined by the geometry of the lattice, not the Poisson’s ratio of the material. A comparative study was performed between thin films supported on lattices with Poisson’s ratio (v = +0.2 and −0.8) lattice to represent a pseudo-uniaxial and complex strain case, respectively. The uniaxial strain lattice demonstrated similar craze propagation, area fraction, and craze interaction behavior to what has been previously observed using traditional methods, e.g. a copper grid support lattice. For the complex strain analysis, the craze appearances observed in the middle section of the bowtie reflected what was expected for the uniaxial case while the end region showed a biaxial strain field. A potential for shearing was noted in the end of the bowties for the parallel strain direction with crazes growing at 45°. Due to the difference in strain distribution within the complex lattice, a delayed onset was observed in the bowtie end region parallel to strain direction. The initial results of complex crazing using an auxetic lattice was successful in demonstrating how crazes behave under a strain field on an auxetic lattice support with v = -0.8.
{"title":"Complex plastic deformation in glassy thin polymer films on 3D-printed auxetic lattices","authors":"Kenya Hazell , Anesia Auguste , Andrew Gillman , Lawrence F. Drummy","doi":"10.1016/j.eml.2025.102422","DOIUrl":"10.1016/j.eml.2025.102422","url":null,"abstract":"<div><div>Traditionally, plastic deformation and the micromechanics of thin polymer films have been evaluated under uniaxial or linear strain. As the use of thin film polymeric materials continues to expand into applications in flexible electronics, gas separation, energy storage and sensing, more work needs to be done to understand how these materials behave under realistic conditions. Concurrently, certain mechanical metamaterials offer the ability to investigate non-linear and multi-axis micromechanics through lattice structures with designed spatially-varying complex strain fields. While previous studies using a support structure have been performed to study polymer crazing in thin films under biaxial or shear conditions, their behavior under complex strain has not been reported. This work offers a new method in which complex strain analysis in polymer films can be performed using an auxetic support lattice with a designed Poisson’s ratio (<em>v</em>) that is defined by the geometry of the lattice, not the Poisson’s ratio of the material. A comparative study was performed between thin films supported on lattices with Poisson’s ratio (<em>v</em> = +0.2 and −0.8) lattice to represent a pseudo-uniaxial and complex strain case, respectively. The uniaxial strain lattice demonstrated similar craze propagation, area fraction, and craze interaction behavior to what has been previously observed using traditional methods, e.g. a copper grid support lattice. For the complex strain analysis, the craze appearances observed in the middle section of the bowtie reflected what was expected for the uniaxial case while the end region showed a biaxial strain field. A potential for shearing was noted in the end of the bowties for the parallel strain direction with crazes growing at 45°. Due to the difference in strain distribution within the complex lattice, a delayed onset was observed in the bowtie end region parallel to strain direction. The initial results of complex crazing using an auxetic lattice was successful in demonstrating how crazes behave under a strain field on an auxetic lattice support with <em>v</em> = -0.8.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102422"},"PeriodicalIF":4.5,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145579560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Morphing surfaces provide a versatile tool to advance the functionalities of high-performance aircraft, soft robots, biomedical devices, and human–machine interfaces. However, achieving precise shape transformation and mechanical property control remains challenging due to nonlinearity, design constraints, and the difficulty of coordinating multiple constituent materials across a continuous surface. To this end, this study unveils that Kirigami art can inspire novel solutions. More specifically, the geometric principles of Kirigami can be exploited to design and fabricate fluidic morphing surfaces capable of highly accurate shape morphing and output force control, all via a single pressure input. This study presents a systematic approach to designing Kirigami for tuning the local deformation and force output through extensive nonlinear modeling and experiment validation on two archetypal patterns: concentric square and circular cuts. The potentials of this approach are demonstrated via two multiphysics case studies: (1) an acoustic holography lens for ultrasonic wave steering, achieving highly accurate deformation control under a single global pressure input, and (2) a haptic device with a small volume, constant contact area, and high-resolution output force. The fluidic Kirigami concept allows for simple yet effective adaptation to different shape and stiffness requirements, paving the way for a new family of scalable and programmable morphing surfaces.
{"title":"High-precision fluidic Kirigami morphing surface for ultrasonic holographic lensing and haptic interfacing","authors":"Ardalan Kahak , Moustafa Sayed Ahmed , Nahid Kalantaryardebily , Hrishikesh Kulkarni , Netta Gurari , Shima Shahab , Suyi Li","doi":"10.1016/j.eml.2025.102424","DOIUrl":"10.1016/j.eml.2025.102424","url":null,"abstract":"<div><div>Morphing surfaces provide a versatile tool to advance the functionalities of high-performance aircraft, soft robots, biomedical devices, and human–machine interfaces. However, achieving <em>precise</em> shape transformation and mechanical property control remains challenging due to nonlinearity, design constraints, and the difficulty of coordinating multiple constituent materials across a continuous surface. To this end, this study unveils that Kirigami art can inspire novel solutions. More specifically, the geometric principles of Kirigami can be exploited to design and fabricate fluidic morphing surfaces capable of highly accurate shape morphing and output force control, all via a single pressure input. This study presents a systematic approach to designing Kirigami for tuning the local deformation and force output through extensive nonlinear modeling and experiment validation on two archetypal patterns: concentric square and circular cuts. The potentials of this approach are demonstrated via two multiphysics case studies: (1) an acoustic holography lens for ultrasonic wave steering, achieving highly accurate deformation control under a single global pressure input, and (2) a haptic device with a small volume, constant contact area, and high-resolution output force. The fluidic Kirigami concept allows for simple yet effective adaptation to different shape and stiffness requirements, paving the way for a new family of scalable and programmable morphing surfaces.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102424"},"PeriodicalIF":4.5,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145579561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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