scholarly journals Study on the Elastoplastic Damage-Healing Coupled Constitutive Model of Mudstone

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Jie Xu ◽  
Jiawang Qu ◽  
Yufeng Gao ◽  
Ning Xu
Keyword(s):  
Mechanical Properties ◽  
Damage Mechanics ◽  
Chemical Interaction ◽  
Triaxial Compression ◽  
Healing Process ◽  
Great Influence ◽  
Radioactive Nuclide ◽  
Self Healing ◽  
Damage Healing ◽  
Elastoplastic Damage

Under the effect of high ground stress and water-rock chemical interaction, the fractures in the damaged mudstone wound undergo a self-healing process and recover the physical and mechanical properties, which has a significant impact on the wall-rock’s stability of high level radioactive waste repository and the migration of radioactive nuclide. According to the general thermodynamics and continuum damage mechanics, an internal variable describing mudstone healing properties is introduced and an elastoplastic damage-healing model reflecting mudstone deformation, damage, and self-healing evolution is put forward. This model is used to simulate the triaxial compression test of mudstone under different confining pressures, whose simulated results are compared with the test data. It is indicated that the model could embody the main mechanical properties of mudstone with the healing effect in an effective way, and the healing part of the model has a great influence on the simulated results.

scholarly journals A theory of anisotropic healing and damage mechanics of materials

2011 ◽  
Vol 468 (2137) ◽  
pp. 163-183 ◽  
Author(s):  
George Z. Voyiadjis ◽  
Amir Shojaei ◽  
Guoqiang Li ◽  
Peter I. Kattan
Keyword(s):  
Smart Materials ◽  
Inelastic Deformation ◽  
Damage Mechanics ◽  
Shape Memory Polymer ◽  
Healing Process ◽  
Continuum Damage Mechanics ◽  
Self Healing ◽  
Healing System ◽  
Damage Healing ◽  
Healing Processes

Self-healing smart materials have emerged into the research arena and have been deployed in industrial and biomedical applications, in which the modelling techniques and predicting schemes are crucial for designers to optimize these smart materials. In practice, plastic deformation is coupled with damage and healing in these systems, which necessitates a coupled formulation for characterization. The thermodynamics of inelastic deformation, damage and healing processes are incorporated here to establish the coupled constitutive equations for healing materials. This thermodynamic consistent formulation provides the designers with the ability to predict the irregular inelastic deformation of glassy polymers and damage and healing patterns for a highly anisotropic self-healing system. Moreover, the lack of a physically consistent method to measure and calibrate the healing process in the literature is addressed here. Within the continuum damage mechanics (CDM) framework, the physics of damage and healing processes is used to introduce the healing effect into the CDM concept and a set of two new anisotropic damage–healing variables are derived. These novel damage–healing variables together with the proposed thermodynamic consistent coupled theory constitute a well-structured method for accurately predicting the degradation and healing mechanisms in material systems. The inelastic and damage response for a shape memory polymer-based self-healing system is captured herein. While the healing experimental results are limited in the literature, the proposed theory provides the mathematical competency to capture the most nonlinear responses.

A Semi-Analytic Solution for Self-Healing Concrete Beams Through Stress Spectral Decomposition

2018 ◽  
Vol 10 (07) ◽  
pp. 1850077
Author(s):  
A. Kazemi ◽  
M. Baghani ◽  
H. Shahsavari ◽  
S. Sohrabpour
Keyword(s):  
Cross Section ◽  
Spectral Decomposition ◽  
Damage Mechanics ◽  
Concrete Beam ◽  
Rectangular Cross Section ◽  
Closed Form Solution ◽  
The Self ◽  
Continuum Damage ◽  
Self Healing ◽  
Damage Healing

Continuum damage-healing mechanics (CDHM) is used for phenomenological modeling of self-healing materials. Self-healing materials have a structural capability to recover a part of the damage for increasing materials life. In this paper, a semi-analytic modeling for self-healing concrete beam is performed. Along this purpose, an elastic damage-healing model through spectral decomposition technique is utilized to investigate an anisotropic behavior of concrete in tension and compression. We drive an analytical closed-form solution of the self-healing concrete beam. The verification of the solution is shown by solving an example for a simply supported beam having uniformly distributed the load. Finally, a result of a self-healing concrete beam is compared to elastic one to demonstrate the capability of the proposed analytical method in simulating concrete beam behavior. The results show that for the specific geometry, the self-healing concrete beam tolerates 21% more weight, and the deflection of the entire beam up to failure load is about 27% larger than elastic solution under ultimate elastic load for both I-beam and rectangular cross-section. Comparison of Continuum Damage Mechanics (CDM) solution with CDHM solution of beam shows that critical effective damage is decreased by 32.4% for a rectangular cross-section and by 24.2% for I-shape beam made of self-healing concrete.

Mechanics of damage, healing, damageability, and integrity of materials: A conceptual framework

2016 ◽  
Vol 26 (1) ◽  
pp. 50-103 ◽  
Author(s):  
George Z Voyiadjis ◽  
Peter I Kattan
Keyword(s):  
Damage Mechanics ◽  
Healing Process ◽  
Continuum Damage Mechanics ◽  
Damage Variable ◽  
Continuum Damage ◽  
Variable Section ◽  
Damage Healing ◽  
Characterization Of Materials ◽  
New Formulation

In this work several new and fundamental concepts are proposed within the framework of continuum damage mechanics. These concepts deal primarily with the nature of the two processes of damage and healing along with introducing a consistent and systematic definition for the concepts of damageability and integrity of materials. Toward this end, seven sections are presented as follows: “The logarithmic damage variable” section introduces the logarithmic and exponential damage variables and makes comparisons with the classical damage variable. In “Integrity and damageability of materials” section a new formulation for damage mechanics is presented in which the two angles of damage–integrity and healing–damageability are introduced. It is shown that both the damage variable and the integrity variable can be derived from the damage–integrity angle while the healing variable and damageability variable are derived from the healing–damageability angle. “The integrity field” section introduces the new concept of the integrity field while “The healing field” section introduces the new concept of the healing field. These two fields are introduced as a generalization of the classical concepts of damage and integrity. “Unhealable damage and nondamageable integrity” section introduces the new and necessary concept of unrecoverable damage or unhealable damage. In this section the concept of permanent integrity or nondamageable integrity is also presented. In “Generalized nonlinear healing” section generalized healing is presented where a distinction is clearly made between linear healing and nonlinear healing. As an example of nonlinear healing the equations of quadratic healing are derived. Finally in “Dissection of the healing process” section a complete and logical/mathematical dissection is made of the healing process. It is hoped that these new and fundamental concepts will pave the way for new, consistent, and holistic avenues in research in damage mechanics and characterization of materials.

scholarly journals An Innovative Approach for Restoring the Mechanical Properties of Thermoplastic-Matrix Nanocomposite by the Use of Partially Polymerized Cyclic Butylene Terephthalate

2020 ◽  
Vol 4 (4) ◽  
pp. 146
Author(s):  
Francesca Ferrari ◽  
Antonio Greco
Keyword(s):  
Mechanical Properties ◽  
Healing Process ◽  
Self Healing ◽  
Butylene Terephthalate ◽  
Thermoplastic Matrix ◽  
Damaged Zone ◽  
Cyclic Butylene Terephthalate ◽  
Flexural Tests ◽  
Activation Times ◽  
Matrix Nanocomposite

This work is focused on the production of a smart material from cyclic butylene-terephthalate (CBT), characterized by the built-in capability to recover its damage, through the catalyzed ring opening polymerization (ROP) of its oligomers; in particular, molten CBT, after filling the damaged zone, can be converted into poly-butylene terephthalate (PBT), thus promoting a join of the broken surfaces and fixing the crack. To obtain a material with self-healing potential, the production of a partially polymerized system is required. For this purpose, two solutions were studied: the first one involved the use of two catalysts with different activation times, whereas the second solution implied the intercalation of the faster catalyst inside the nanoclay lamellae. Since the intercalation allowed slowing the activation of the catalyst, residual CBT can be converted in a second step. Mechanical properties of partially reacted PBT samples and their healing ability were checked by flexural analyses; in order to promote the healing process, samples were notched to simulate partial damage and left in oven for different times and temperatures, to allow the activation of the unreacted catalyst with the consequent ROP of the residual CBT; flexural tests on samples after healing showed a good recovery of mechanical properties.

Soluble Silicates as Additives for Self-Sealing and Self-Healing Concrete

2016 ◽  
Vol 1813 ◽  
Author(s):  
L. E. Rendon Diaz Miron ◽  
M. E. Lara Magaña
Keyword(s):  
Mechanical Properties ◽  
Crack Formation ◽  
Healing Process ◽  
Self Healing ◽  
Reaction Products ◽  
Calcium Carbonate Precipitation ◽  
Broad Perspective ◽  
Healing Efficiency ◽  
Tensile Forces ◽  
Solubility Ratio

ABSTRACTTensile strength of concrete is limited and therefore is sensitive to crack formation. Steel reinforcement is added to bear the tensile forces; nonetheless, this does not completely omit crack formation. Repair of cracks in concrete is time-consuming and expensive. Self-sealing and self-healing of cracks upon appearance would therefore be a convenient property. We propose a mechanism to obtain self-repair of the concrete by adding soluble silicates (ASS) which will induce a self-sealing and self-healing process catalyzed by natural periods of wet and dry states of the concrete. Self-sealing approaches prevent the ingress of harsh chemical substances which may deteriorate the concrete matrix. This can be achieved by self-healing of concrete cracks (e.g. further cement hydration, calcium carbonate precipitation) and autonomous healing (e.g. further hydration of partially soluble silicates added as healing agents). The autogenous healing efficiency depends on the amount of deposited reaction products (ASS), its solubility (ratio of calcium to sodium silicate), the availability of water, and the crack width (restricted by adding microfibers). The self-sealing efficiency is generally evaluated by measuring the decrease in water permeability and air flow through the crack. The healing efficiency is usually evaluated by testing concrete´s regain in mechanical properties after crack formation; by reloading the cracked and autonomously healed specimen and comparing the obtained mechanical properties with the original ones. Self-sealing and self-healing of concrete gives a broad perspective and new possibilities to make future concrete structures more durable.

scholarly journals Mechanical Properties Assessment of Low-Content Capsule-Based Self-Healing Structural Composites

2020 ◽  
Vol 10 (17) ◽  
pp. 5739
Author(s):  
Xenia Tsilimigkra ◽  
Dimitrios Bekas ◽  
Maria Kosarli ◽  
Stavros Tsantzalis ◽  
Alkiviadis Paipetis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Mechanical Performance ◽  
Urea Formaldehyde ◽  
Healing Process ◽  
Experimental Results ◽  
Self Healing ◽  
Healing Efficiency ◽  
A Minor

Microcapsule-based carbon fiber reinforced composites were manufactured by wet layup, in order to assess their mechanical properties and determine their healing efficiency. Microcapsules at 10%wt. containing bisphenol-A epoxy, encapsulated in a urea formaldehyde (UF) shell, were employed with Scandium (III) Triflate (Sc (OTf)3) as the catalyst. The investigation was deployed with two main directions. The first monitored changes to the mechanical performance due to the presence of the healing agent within the composite. More precisely, a minor decrease in interlaminar fracture toughness (GIIC) (−14%), flexural strength (−12%) and modulus (−4%) compared to the reference material was reported. The second direction evaluated the healing efficiency. The experimental results showed significant recovery in fracture toughness up to 84% after the healing process, while flexural strength and modulus healing rates reached up to 14% and 23%, respectively. The Acoustic Emission technique was used to support the experimental results by the onsite monitoring.

scholarly journals Healable thermoset polymer composite embedded with stimuli-responsive fibres

2012 ◽  
Vol 9 (77) ◽  
pp. 3279-3287 ◽  
Author(s):  
Guoqiang Li ◽  
Harper Meng ◽  
Jinlian Hu
Keyword(s):  
Mechanical Properties ◽  
Human Skin ◽  
Biological Systems ◽  
Healing Process ◽  
Self Healing ◽  
Stimuli Responsive ◽  
Closed Crack ◽  
Healing Efficiency ◽  
Thermoset Polymer ◽  
Crack Interface

Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable.

scholarly journals A Coupled Elastoplastic Damage Dynamic Model for Rock

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xuelong Hu ◽  
Ming Zhang ◽  
Xiangyang Zhang ◽  
Min Tu ◽  
Zhiqiang Yin ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Yield Criterion ◽  
Triaxial Compression ◽  
Equivalent Plastic Strain ◽  
Damage Variable ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Elastoplastic Damage

Rock dynamic constitutive model plays an important role in understanding dynamic response and addressing rock dynamic problems. Based on elastoplastic mechanics and damage mechanics, a dynamic constitutive model of rock coupled with elastoplastic damage is established. In this model, unified strength theory is taken as the yield criterion; to reflect the different damage evolution law of rocks under tension and pressure conditions, the effective plastic strain and volumetric plastic strain are used to represent the compressive damage variable and the equivalent plastic strain is used to represent the tensile damage variable; the plastic hardening behavior and strain rate effect of rocks are characterized by piecewise function and dynamic increase factor function, respectively; Fortran language and LS-DYNA User-Defined Interface (Umat) are used to numerically implement the constitutive model; the constitutive model is verified by three classical examples of rock uniaxial and triaxial compression tests, rock uniaxial tensile test, and rock ballistic test. The results show that the constitutive model can describe the dynamic and static mechanical behavior of rock comprehensively.

Modeling microcapsule-enabled self-healing cementitious composite materials using discrete element method

2017 ◽  
Vol 26 (2) ◽  
pp. 340-357 ◽  
Author(s):  
Shuai Zhou ◽  
Hehua Zhu ◽  
J Woody Ju ◽  
Zhiguo Yan ◽  
Qing Chen
Keyword(s):  
Discrete Element Method ◽  
Healing Process ◽  
Compressive Loading ◽  
Discrete Element ◽  
Cementitious Materials ◽  
Self Healing ◽  
Healing Effect ◽  
Healing Agent ◽  
Damage Healing ◽  
Element Method

Concrete with a micro-encapsulated healing agent is appealing due to its self-healing capacity. The discrete element method (DEM) is emerging as an increasingly used approach for investigating the damage phenomenon of materials at the microscale. It provides a promising way to study the microcapsule-enabled self-healing concrete. Based on the experimental observation and DEM, a three-dimensional damage-healing numerical model of microcapsule-enabled self-healing cementitious materials under compressive loading is proposed. The local healing effect can be simulated in our model, as well as the stress concentration effect and the partial healing effect. The healing variable of the DEM model is developed to describe the healing process. We examine the dependence of the mechanical properties of the microcapsule-enabled self-healing material on (a) the stiffness of the solidified healing agent, (b) the strength of the solidified healing agent, (c) the initial damage of specimens, and (d) the partial healing effect. In particular, the proposed numerical damage-healing model demonstrates the potential capability to explain and simulate the physical behavior of microcapsule-enabled self-healing materials on the microscale.

scholarly journals A Heterocyclic Polyurethane with Enhanced Self-Healing Efficiency and Outstanding Recovery of Mechanical Properties

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 968
Author(s):  
Jinsil Kim ◽  
Pyong Hwa Hong ◽  
Kiwon Choi ◽  
Gyeongmin Moon ◽  
Jungsoon Kang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Healing Process ◽  
Supramolecular Network ◽  
Hydroxyl Groups ◽  
Self Healing ◽  
Healing Efficiency ◽  
Bonding Interaction ◽  
Heterocyclic Group ◽  
Polyurethane Matrix ◽  
Strong Hydrogen Bonding Interaction

A functional polyurethane based on the heterocyclic group was synthesized and its self-healing and mechanical properties were examined. To synthesize a heterocyclic polyurethane, a polyol and a heterocyclic compound with di-hydroxyl groups at both ends were blended and the blended solution was reacted with a crosslinker containing multiple isocyanate groups. The heterocyclic polyurethane demonstrates better self-healing efficiency than the conventional polyurethane with no heterocyclic groups. Furthermore, unlike the conventional self-healing materials, the heterocyclic polyurethane examined in this study shows an outstanding recovery of the mechanical properties after the self-healing process. These results are attributed to the unique supramolecular network resulting from the strong hydrogen bonding interaction between the urethane group and the heterocyclic group in the heterocyclic polyurethane matrix.

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