A theory of anisotropic healing and damage mechanics of materials

Voyiadjis, George Z.; Shojaei, Amir; Li, Guoqiang; Kattan, Peter I.

doi:10.1098/rspa.2011.0326

Cited by 84 publications

(92 citation statements)

References 42 publications

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“…Several healing schemes have been reported in the literature primarily for healing microcracks with narrow opening, including incorporation of external healing agents such as liquid healing agent by microcapsules (White et al 2001), hollow fibres (Pang & Bond 2005) and microvascular networks (Toohey et al 2007), and solid healing agent such as embedded thermoplastic particles (TPs; Zako & Takano 1999;Voyiadjis et al 2012a). Some polymers such as ionomers (Plaisted & Nemat-Nasser 2007;Varley & van der Zwaag 2008) and thermally reversible covalent bonds (TRCBs; Liu & Chen 2007) by themselves possess healing capabilities.…”

Section: Introductionmentioning

confidence: 99%

A viscoplastic theory of shape memory polymer fibres with application to self-healing materials

Shojaei

2012

Proc. R. Soc. A.

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103

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The difficulty in healing structural damage is that most existing schemes need external help to bring the fractured surfaces in contact before healing can occur. To facilitate the existing schemes to heal macroscopic cracks, we envision that the cracked surfaces can be brought in contact through constrained shape recovery of a shape memory polymer (SMP) fibre-reinforced grid skeleton that is embedded in thermoset polymer matrix, similar to stitch a cut in the human skin by suture. In this study, we show that polyurethane SMP fibres can be hardened through cyclic cold-drawing programming, which makes them suitable for reinforcement and healing in thermoset polymer composites. We characterized the microstructure of the SMP fibres, which provides fundamental understanding of the effect of programming on the degree of crystallinity and molecular orientation. Then, a micromechanical multiscale viscoplastic theory is developed to predict the thermomechanical behaviours of the SMP fibres, including the cyclic hardening and stress recovery responses. The proposed theory takes into account the stress-induced crystallization process and the evolution of the morphological texture based on the applied stresses. The cyclic loading and the thermomechanical responses of the SMP fibres confirm the capabilities of the proposed model in capturing these phenomena.

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Section: Introductionmentioning

confidence: 99%

A viscoplastic theory of shape memory polymer fibres with application to self-healing materials

Shojaei

2012

Proc. R. Soc. A.

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103

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“…As depicted in figure 1, the holding time during the programming has a direct impact on the magnitude of the shape fixity ratio (SFR) obtained after the unloading process and also on the SRR measured through unconstrained heating process, i.e. free recovery [2,4,13,14,22,36,55]. The effect of the holding time (or structural relaxation time) on the SRR is captured through F t rel function, and an empirical constitutive relation is defined for this function as follows:…”

Section: (A) Shape Recovery Modellingmentioning

confidence: 99%

“…In the case of polymeric materials, the MD mechanisms can be correlated to the molecular chain failures in the polymeric network. The accumulation of the failed chains may result in the loss of the mechanical properties of polymers such as a gradual reduction in the elastic tensile modulus [55,57]. In the case of ductile or low cycle fatigue, the MD damage parameter is constitutively developed by [22,23,54,58] …”

Section: (A) Mechanical Damagesmentioning

confidence: 99%

Thermomechanical constitutive modelling of shape memory polymer including continuum functional and mechanical damage effects

Shojaei

2014

Proc. R. Soc. A.

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A multi-mechanism-based phenomenological model is developed within the finite deformation kinematics framework for capturing the thermomechanical behaviour of shape memory polymers (SMPs) both during programming and in service. Particularly, the damage mechanisms in SMPs are studied within the continuum damage mechanics (CDMs) framework in which they are classified into mechanical or physical damage, induced during service condition, e.g. fatigue and functional damage induced during thermomechanical cycles, e.g. shape recovery loss. Statistical mechanics is incorporated to describe the initiation and saturation of these deformation mechanisms. The main advantage of the presented viscoplastic model, comparing to the existing counterparts, is its simplicity by minimizing the need for curve fitting, and capability in simulating the nonlinear stress-strain behaviour of amorphous, crystalline or semicrystalline SMPs. The developed viscoplastic CDM model takes into account several distinctive deformation mechanisms involved in the thermomechanical cycle of SMPs, including glass transition loss events, temperature-dependent material properties, stress relaxation, shape recovery transient events and damage effects. The established model correlates well with the experimental results and its computational capabilities provide material designers with a powerful design tool for future SMP applications.

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“…In damage and healing mechanics, an effective damage variable ' eff is derived as follows (Darabi et al, 2012;Voyiadjis et al, 2011Voyiadjis et al, , 2012aVoyiadjis et al, , 2012b)…”

Section: Damageability Variablementioning

confidence: 99%

“…In addition, there have been some notable research efforts in the corresponding subject of healing mechanics (Darabi et al, 2012;Voyiadjis et al, 2011Voyiadjis et al, , 2012aVoyiadjis et al, , 2012b. Some of the recent research efforts are seen to be in the form of combined damage/healing models for different types of materials.…”

Section: Introductionmentioning

confidence: 99%

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

Voyiadjis

Kattan

2016

International Journal of Damage Mechanics

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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.

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A theory of anisotropic healing and damage mechanics of materials

Cited by 84 publications

References 42 publications

A viscoplastic theory of shape memory polymer fibres with application to self-healing materials

A viscoplastic theory of shape memory polymer fibres with application to self-healing materials

Thermomechanical constitutive modelling of shape memory polymer including continuum functional and mechanical damage effects

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

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