scholarly journals Competition between delamination and tearing in multiple peeling problems

2019 ◽  
Vol 16 (160) ◽  
pp. 20190388 ◽  
Author(s):  
Lucas Brely ◽  
Federico Bosia ◽  
Stefania Palumbo ◽  
Massimiliano Fraldi ◽  
Ali Dhinojwala ◽  
...  
Keyword(s):  
Numerical Model ◽  
Mechanical Performance ◽  
Dissipated Energy ◽  
Complex Structures ◽  
Adhesive Systems ◽  
Complex Interplay ◽  
Spider Web ◽  
Interface Delamination ◽  
Adhesive Energy ◽  
Parameter Ranges

Adhesive attachment systems consisting of multiple tapes or strands are commonly found in nature, for example in spider web anchorages or in mussel byssal threads, and their structure has been found to be ingeniously architected in order to optimize mechanical properties: in particular, to maximize dissipated energy before full detachment. These properties emerge from the complex interplay between mechanical and geometric parameters, including tape stiffness, adhesive energy, attached and detached lengths and peeling angles, which determine the occurrence of three main mechanisms: elastic deformation, interface delamination and tape fracture. In this paper, we introduce a formalism to evaluate the mechanical performance of multiple tape attachments in different parameter ranges, where an optimal (not maximal) adhesion energy emerges. We also introduce a numerical model to simulate the multiple peeling behaviour of complex structures, illustrating its predictions in the case of the staple-pin architecture. Finally, we present a proof-of-principle experiment to illustrate the predicted behaviour. We expect the presented formalism and the numerical model to provide important tools for the design of bioinspired adhesive systems with tuneable or optimized detachment properties.

scholarly journals Numerical implementation of multiple peeling theory and its application to spider web anchorages

2015 ◽  
Vol 5 (1) ◽  
pp. 20140051 ◽  
Author(s):  
Lucas Brely ◽  
Federico Bosia ◽  
Nicola M. Pugno
Keyword(s):  
Numerical Model ◽  
Numerical Approach ◽  
Complex Structures ◽  
Numerical Implementation ◽  
Spider Web ◽  
Complex Architectures ◽  
Fibrillar Adhesives

Adhesion of spider web anchorages has been studied in recent years, including the specific functionalities achieved through different architectures. To better understand the delamination mechanisms of these and other biological or artificial fibrillar adhesives, and how their adhesion can be optimized, we develop a novel numerical model to simulate the multiple peeling of structures with arbitrary branching and adhesion angles, including complex architectures. The numerical model is based on a recently developed multiple peeling theory, which extends the energy-based single peeling theory of Kendall, and can be applied to arbitrarily complex structures. In particular, we numerically show that a multiple peeling problem can be treated as the superposition of single peeling configurations even for complex structures. Finally, we apply the developed numerical approach to study spider web anchorages, showing how their function is achieved through optimal geometrical configurations.

scholarly journals Tuning Physical Crosslinks in Hybrid Hydrogels for Network Structure Analysis and Mechanical Reinforcement

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 352 ◽  
Author(s):  
Xue Lv ◽  
Chuang Liu ◽  
Zhubao Shao ◽  
Shulin Sun
Keyword(s):  
Mechanical Strength ◽  
Large Scale ◽  
Mechanical Performance ◽  
Structural Parameters ◽  
Industrial Applications ◽  
Dissipated Energy ◽  
Small Scale ◽  
Hybrid Particles ◽  
Mechanical Reinforcement ◽  
Hybrid Hydrogels

Hydrogels with high mechanical strength are needed for a variety of industrial applications. Here, a series of hydrogels was prepared by introducing hybrid particles as hydrophobic association points to toughen the hydrogels. These toughened hydrogels were able to transfer an external mechanical force via the reorganization of the crosslinking networks. They exhibited an extraordinary mechanical performance, which was the result of the coordination between hydrophobic segments and hybrid particles. Herein, the connection between the dissipated energy of the inner distribution structure (on a small scale) and the mechanical properties (on a large scale) was conducted. Specifically, we inspected hydrogels of latex particles (LPs) with different chain lengths (C4, C12, C18) and studied their inner structural parameters, namely, the relationship between the density and molecular weight of crosslinking points to the mechanical strength and energy dissipation. Favorable traits of the hydrogels included compact internal structures that were basically free from defects and external structures with puncture resistance, high toughness, etc. Based on the experimental results that agreed with the theoretical results, this study provides a profound understanding of the internal structure of hydrogels, and it offers a new idea for the design of high-strength hybrid hydrogels.

scholarly journals Seismic Damage Model of Bridge Piers Subjected to Biaxial Loading Considering the Impact of Energy Dissipation

2019 ◽  
Vol 9 (7) ◽  
pp. 1481 ◽  
Author(s):  
Shangshun Lin ◽  
Zhanghua Xia ◽  
Jian Xia
Keyword(s):  
Energy Dissipation ◽  
Structural Damage ◽  
Biaxial Loading ◽  
Mechanical Performance ◽  
Damage Model ◽  
Damage Index ◽  
Seismic Damage ◽  
Bridge Piers ◽  
Dissipated Energy ◽  
The Impact

The large degradation of the mechanical performance of hollow reinforced concrete (RC) bridge piers subjected to multi-dimensional earthquakes has not been thoroughly assessed. This paper aims to improve the existing seismic damage model to assess the seismic properties of tall, hollow RC piers subjected to pseudo-static, biaxial loading. Cyclic bilateral loading tests on fourteen 1/14-scale pier specimens with different slenderness ratios, axial load ratios, and transverse reinforcement ratios were carried out to investigate the damage propagation and the cumulative dissipated energy with displacement loads. By considering the influence of energy dissipation on structural damage, a new damage model (M-Usami model) was developed to assess the damage characteristics of hollow RC piers. The results present four consecutive damage stages during the loading process: (a) cracking on concrete surface, (b) yielding of longitudinal reinforcements; (c) spalling of concrete, and (d) collapsing of pier after the concrete crushed and the longitudinal bars ruptured due to the flexural failure. The damage level caused by the seismic waves can be reduced by designing specimens with a good seismic energy dissipation capacity. The theoretical damage index values calculated by the M-Usami model agreed well with the experimental observations. The developed M-Usami model can provide insights into the approaches to assessing the seismic damage of hollow RC piers subjected to bilateral seismic excitations.

A FEA Simulation Model for Thin-Walled C-Section Composite Beam Assembling With R-Angle Deviation

2014 ◽  
Author(s):  
Hua Wang ◽  
Suo Si
Keyword(s):  
Numerical Model ◽  
Composite Beam ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Element Model ◽  
Load Level ◽  
Compression Tests ◽  
Accurate Analysis ◽  
Angle Deviation ◽  
Thin Walled

There are unavoidable deviations, such as shrinkage and distortions, in the composite detail parts production due to the complexity of composites fabrication. Interests in the assembly analysis of composite beams have led to a need for more accurate analysis especially in the case of fabrication deviations. This work proposes a numerical finite element model of thin-walled C-section composite beam with R-angle deviation for assembling. The rule of Hashin failure combined with cohesive element is applied to study the mechanical performance of the fiber and matrix (implemented as user subroutine UMAT in ABAQUS) while positioning and clamping. Tension and compression tests are carried out based on available standards to determine the C-section beam behavior under load. The testing data validates the proposed numerical model. The numerical model captures the experimentally obtained results with minimal error, and predicts the failure modes successfully. The proposed model allows to determine accurately the first failure location and the associated load level. It will enhance the understanding of the composite components pre-loading analysis, and help systematically improving the composites assembling efficiency in civil aircraft industry.

Effect of the frictional coefficient and pre-tension on stress distribution of fabric during the weaving process

2017 ◽  
Vol 88 (8) ◽  
pp. 904-912
Author(s):  
Zhiping Ying ◽  
Zhenyu Wu ◽  
Xudong Hu ◽  
Xiangqing Zhou
Keyword(s):  
Numerical Model ◽  
Stress Distribution ◽  
Mechanical Performance ◽  
Frictional Coefficient ◽  
Woven Fabric ◽  
Weft Yarn ◽  
Tension Stress ◽  
Initial Shape ◽  
Warp Tension ◽  
Fluctuation Range

The non-uniform stress distribution of woven fabric has a significant influence not only on its mechanical performance in service, but also on its weaving efficiency in the fabrication process. For investigating the stress distribution in woven fabric, a numerical model at the yarn scale was established to simulate the interlacing process between the weft and warp yarns using an explicit finite element solver. The yarns were assumed to be a homogeneous continuum and the transversal isotropic constitutive equation was used. A modified lenticular initial shape was used as the cross-section of the yarn and trajectories of warp and weft yarns were set to be straight. The classical Amonton–Coulomb law was used for the tangential behavior between the weft and warp yarns. The simulation results reveal that the interaction between weft and warp yarns consists of three phases in terms of contact, adhesion and sliding. The sectional stress distribution in the weft yarn determined by multi-points contact between a single weft yarn and a group of warp yarns was also analyzed. The tension stress of the weft yarn was larger in the middle part than that in both sides. Based on the numerical model, the effects of two key parameters, namely the frictional coefficient and weft pre-tension, on the stress distribution were discussed in detail. The weft crimp angle and warp tension distribution uniformity decreased as the frictional coefficient decreased, whereas the warp tension fluctuation range did not obviously decrease. However, an improved method by exerting pre-tension in two ends of weft yarn was proposed and the warp tension fluctuation range was significantly decreased. The distribution trend of warp tension obtained from the numerical simulation showed an acceptable tendency with experiment measurements.

Review of Analysis Model on Three-Dimensional Braided Composites

2014 ◽  
Vol 607 ◽  
pp. 881-885
Author(s):  
Hai Yan Chen ◽  
Gao Feng Wei ◽  
Yan Xu
Keyword(s):  
Numerical Model ◽  
Mechanical Performance ◽  
Three Dimensional ◽  
Single Step ◽  
Analysis Model ◽  
Micro Structure ◽  
Braided Composites ◽  
Reinforced Fiber

Because reinforced-fiber has characteristic of single step forming in three-dimensional braided composites, analysis of mechanical performance is very different from laminates. This paper proceeds from the micro-structure of 3-D braided composites, some review and research are presented detailedly, and the several model’s merit and demerit are analyzed, which can conduct dynamicists to choose reasonable numerical model. The mechanical performance can be predicted accurately, and the next research can be guided using above analysis.

scholarly journals In situ three-dimensional spider web construction and mechanics

2021 ◽  
Vol 118 (33) ◽  
pp. e2101296118
Author(s):  
Isabelle Su ◽  
Neosha Narayanan ◽  
Marcos A. Logrono ◽  
Kai Guo ◽  
Ally Bisshop ◽  
...  
Keyword(s):  
Self Assembly ◽  
High Performance ◽  
Mechanical Performance ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Spider Webs ◽  
Spider Web ◽  
Web Geometry ◽  
Under Construction ◽  
The Web

Spiders are nature’s engineers that build lightweight and high-performance web architectures often several times their size and with very few supports; however, little is known about web mechanics and geometries throughout construction, especially for three-dimensional (3D) spider webs. In this work, we investigate the structure and mechanics for a Tidarren sisyphoides spider web at varying stages of construction. This is accomplished by imaging, modeling, and simulations throughout the web-building process to capture changes in the natural web geometry and the mechanical properties. We show that the foundation of the web geometry, strength, and functionality is created during the first 2 d of construction, after which the spider reinforces the existing network with limited expansion of the structure within the frame. A better understanding of the biological and mechanical performance of the 3D spider web under construction could inspire sustainable robust and resilient fiber networks, complex materials, structures, scaffolding, and self-assembly strategies for hierarchical structures and inspire additive manufacturing methods such as 3D printing as well as inspire artistic and architectural and engineering applications.

scholarly journals Effects of Corrosion on Compressive Arch Action and Catenary Action of RC Frames to Resist Progressive Collapse Based on Numerical Analysis

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2662
Author(s):  
Lu Zhang ◽  
Tingyu Wei ◽  
Hongyu Li ◽  
Jian Zeng ◽  
Xiaofang Deng
Keyword(s):  
Numerical Model ◽  
Mechanical Performance ◽  
Progressive Collapse ◽  
Significant Loss ◽  
Catenary Action ◽  
Rc Frames ◽  
Collapse Resistance ◽  
Arch Action ◽  
Rebar Corrosion ◽  
Modeling Strategy

Many negative factors can influence the progressive collapse resistance of reinforced concrete (RC) frame structures. One of the most important factors is the corrosion of rebar within the structure. With increasing severity of corrosion, the duration, robustness, and mechanical performance can be greatly impaired. One specific side effect of rebar corrosion is the significant loss of protection against progressive collapse. In order to quantify the effects of rebar corrosion on load-resisting mechanisms (compressive arch action (CAA) and tensile catenary action (TCA)) of RC frames, a series of numerical investigations were carried out in this paper. The previous experimental results reported in the literature provide a benchmark for progressive collapse behavior as a sound condition and validate the proposed numerical model. Furthermore, based on the verified numerical model, the CAA and TCA with increasing corrosion and an elapsed time from 0 to 70 years are investigated. Comparing with the conventional empirical model, the proposed numerical model has shown the ability and feasibility in predicting the collapse resistance capacity in structures with corroded rebar. Therefore, this numerical modeling strategy provides comprehensive insights into the change of load-resisting mechanisms in these structures, which can be beneficial for optimizing the design.

scholarly journals Influence of Air Plasma Pretreatments on Mechanical Properties in Metal-Reinforced Laminated Wood

2022 ◽  
Vol 8 ◽  
Author(s):  
Sebastian Dahle ◽  
Kavyashree Srinivasa ◽  
Jure Žigon ◽  
Arnaud Maxime Cheumani Yona ◽  
Georg Avramidis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Mechanical Load ◽  
Urea Formaldehyde ◽  
Air Plasma ◽  
Adhesive Systems ◽  
Plasma Treatments ◽  
Structural Applications ◽  
The Impact

The use of wood-based materials in building and construction is constantly increasing as environmental aspects and sustainability gain importance. For structural applications, however, there are many examples where hybrid material systems are needed to fulfil the specific mechanical requirements of the individual application. In particular, metal reinforcements are a common solution to enhance the mechanical properties of a wooden structural element. Metal-reinforced wood components further help to reduce cross-sectional sizes of load-bearing structures, improve the attachment of masonry or other materials, enhance the seismic safety and tremor dissipation capacity, as well as the durability of the structural elements in highly humid environments and under high permanent mechanical load. A critical factor to achieve these benefits, however, is the mechanical joint between the different material classes, namely the wood and metal parts. Currently, this joint is formed using epoxy or polyurethane (PU) adhesives, the former yielding highest mechanical strengths, whereas the latter presents a compromise between mechanical and economical constraints. Regarding sustainability and economic viability, the utilization of different adhesive systems would be preferable, whereas mechanical stabilities yielded for metal-wood joints do not permit for the use of other common adhesive systems in such structural applications. This study extends previous research on the use of non-thermal air plasma pretreatments for the formation of wood-metal joints. The plasma treatments of Norway spruce [Picea abies (L.) Karst.] wood and anodized (E6/EV1) aluminum AlMgSi0.5 (6060) F22 were optimized, using water contact angle measurements to determine the effect and homogeneity of plasma treatments. The adhesive bond strengths of plasma-pretreated and untreated specimens were tested with commercial 2-component epoxy, PU, melamine-urea formaldehyde (MUF), polyvinyl acetate (PVAc), and construction adhesive glue systems. The influence of plasma treatments on the mechanical performance of the compounds was evaluated for one selected glue system via bending strength tests. The impact of the hybrid interface between metal and wood was isolated for the tests by using five-layer laminates from three wood lamellae enclosing two aluminum plates, thereby excluding the influence of congeneric wood-wood bonds. The effect of the plasma treatments is discussed based on the chemical and physical modifications of the substrates and the respective interaction mechanisms with the glue systems.

The Leeuwenhoek Lecture - The dynamics of viral functions

1961 ◽  
Vol 154 (954) ◽  
pp. 1-20 ◽  
Keyword(s):  
Molecular Dynamics ◽  
Infected Cell ◽  
Malignant Cell ◽  
Living Cells ◽  
Complex Structures ◽  
Complex Interplay ◽  
Lysogenic Bacterium ◽  
A Cell ◽  
Virus System ◽  
Viral Reproduction

The ultimate aim of biochemistry, wrote Sir Frederick Gowland Hopkins (1933), should be an adequate and acceptable description of molecular dynamics in living cells and tissues. My ambition, in this eleventh Leeuwenhoek Lecture, is to describe some aspects of the molecular dynamics of viral functions. A specific entity which is unable to multiply could not be a virus. The proper activity of a virus, the viral function par excellence, is consequently reproduction. Yet viral reproduction involves, not one, but a whole set of functions, for viruses, despite their reputation, are highly complex structures. In order that the lecture should not appear as the expression of an esoteric and impervious doctrinal corpus, we have to state first what we understand by the term virus, a necessary step in view of the fact that this is the fifth Leeuwenhoek Lecture dealing with viruses. It will also be necessary to explain the meaning of a very few unfamiliar terms. This done, a virus will be introduced into a cell and we shall try to understand how it develops. An infected cell may either die or survive. Sometimes a new balanced cell-virus system emerges, such as a lysogenic bacterium or a malignant cell. The complex interplay of cellular and viral functions will be analyzed. Then the current views concerning the mechanisms by which a cell regulates its functions will be summarized. This will lead finally to a discussion of the relation of viruses to regulating systems in general.

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