Fatigue crack propagation in microcapsule-toughened epoxy

Brown, Eric N.; White, Scott R.; Sottos, Nancy R.

doi:10.1007/s10853-006-0512-y

Cited by 161 publications

(108 citation statements)

References 34 publications

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“…The toughening effect is also reflected by a change in fracture morphology from mirror-like of the unfilled epoxy to hackle markings of the capsules filled version ( Figure 5). The result coincides with previous report on a similar system, where crack pinning mechanism was believed to take the responsibility [13,14,17]. Such an increase of material's toughness would inevitably improve its fatigue performance because of the increased resistance to fatigue crack propagation.…”

Section: Effect Of Microcapsules On Fatiguesupporting

confidence: 91%

Self-healing of fatigue crack in epoxy materials with epoxy/mercaptan system

Yuan¹,

Rong²,

Zhang³

et al. 2011

Express Polym. Lett.

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Abstract. Successful retardation or arrest of fatigue crack is observed in self-healing epoxy composite containing dual encapsulated healant, i.e. two types of microcapsules that respectively include epoxy prepolymer and mercaptan/tertiary amine hardener. Fast curing of the released healing agent from the broken capsules leads to rapid development of its bonding strength and fracture toughness at room temperature. It is found that the effects of microcapsules induced-toughening, hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent are responsible for the extension of fatigue life. Depending on the applied stress intensity range, !KI, and the competition between polymerization kinetics of the healing agent and crack growth rate, the above mechanisms exert different influences on crack retardation. The results might serve as a reference for further improving the performance of the healant system under fatigue circumstances. Vol.5, No.1 (2011) 47-59 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2011.6 * Corresponding author, e-mail: ceszmq@mail.sysu.edu.cn © BME-PT responding to propagating fatigue cracks by autonomic processes that led to higher endurance limit and life extension, or even complete arrest of cracking [5][6][7][8], in addition to the ability to repair the cracks generated by monotonic fracture [9]. The degree of fatigue life extension was found to be dependent on the relative magnitude of mechanical kinetics of crack propagation and chemical kinetics of healing. In our previous work [12], the epoxy/mercaptan/ tertiary amine healing system proved to be able to suppress and rehabilitate fatigue crack in epoxy materials via manual infiltration. Effect of adhesive curing process on fatigue crack propagation was studied in detail. As a continuation of our project, the present paper is focused on self-healing of fatigue crack in epoxy composites containing dual encapsulated healant, i.e. two types of microcapsules that respectively include epoxy prepolymer as the polymerizable component and mercaptan/tertiary amine catalyst as the hardener. The knowledge might provide deeper understanding of the healant for future application. Keywords: smart polymers, fracture and fatigue, self-healing, epoxy eXPRESS Polymer Letters Experimental 2.1. Materials and specimen preparationThe encapsulated healing agent, poly(melamineformaldehyde)-walled capsules containing epoxy and its hardener, was made according to the methods described elsewhere [13]. The epoxy-loaded microcapsules hold a 1:1 weight ratio mixture of diglycidyl ether of bisphenol A (EPON 828, Hexion Specialty Chemicals, Columbus, USA) and diglycidyl ether of resorcin (J-80, Wuxi Resin Factory of Bluestar New Chemical Materials Co., Ltd., Jiangsu, China), while the hardener-loaded microcapsules include pentaerythritol tetrakis (3-mercaptopropionate) (PMP, Fluka Chemie AG, Buchs, Switzerland) and 2,4,6-tris(dimethylaminomethyl) phenol (DMP-30, Shanghai Medical Group Reagent C...

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Section: Effect Of Microcapsules On Fatiguesupporting

confidence: 91%

Self-healing of fatigue crack in epoxy materials with epoxy/mercaptan system

Yuan¹,

Rong²,

Zhang³

et al. 2011

Express Polym. Lett.

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“…The rupture of microcapsules is the mechanical trigger to the healing process and without it, no healing occurs. This system has proven to be highly effective at healing cracks in both quasi-static [1] and fatigue [3][4][5][6] loading.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Microcapsules Used in a Self-Healing Polymer

2006

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The elastic modulus and failure behavior of poly(urea-formaldehyde) shelled microcapsules were determined through single-capsule compression tests. Capsules were tested both dry and immersed in a fluid isotonic with the encapsulent. The testing of capsules immersed in a fluid had little influence on mechanical behavior in the elastic regime. Elastic modulus of the capsule shell wall was extracted by comparison with a shell theory model for the compression of a fluid filled microcapsule. Average capsule shell wall modulus was 3.7 GPa, regardless of whether the capsule was tested immersed or dry. Microcapsule diameter was found to have a significant effect on failure strength, with smaller capsules sustaining higher loads before failure. Capsule size had no effect on the modulus value determined from comparison with theory.

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“…Load line crack opening displacement (COD) was measured by a clip gauge. Crack lengths were measured optically and by specimen compliance [23]. Due to the complexity of healing a growing crack under fatigue circumstances, retardation and arrest of fatigue cracks were found to be dependent on the range of applied cyclic stress intensity, ΔK I , as well as the competition between polymerization kinetics of the healing agent and crack growth rate [5][6][7][8].…”

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confidence: 99%

Healing of fatigue crack in epoxy materials with epoxy/mercaptan system via manual infiltration

Yuan¹,

Rong²,

Zhang³

et al. 2010

Express Polym. Lett.

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Abstract. The present work verified the capability of epoxy/mercaptan/tertiary amine system for retarding and/or arresting fatigue cracks in epoxy materials subjected to cyclic loading at room temperature. By using static and dynamic manual infiltration methods, the effects of hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent were revealed. Depending on the applied stress intensity range and the competition between polymerization kinetics of the healing agent and crack growth rate, the above mechanisms exerted different influences on crack retardation under different circumstances. On the whole, the epoxy/mercaptan/tertiary amine system proved to be very effective in obstructing fatigue crack propagation. It formed a promising base for developing self-healing epoxy materials that enable in-situ autonomic rehabilitation of fatigue crack. Vol.4, No.10 (2010) 644-658 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2010.79 dling strength in minutes at room temperature and develop useful bond strengths at ambient temperatures as low as -20°C. Therefore, it should be favorable for repairing fatigue damages under cyclic loading. In our previous work, self-healing epoxy composites containing dual encapsulated healant, i.e. two types of microcapsules that respectively include epoxy prepolymer as the polymerizable component and mercaptan/tertiary amine catalyst as the hardener, were made [18][19][20][21]. Upon fracture the unreacted epoxy can be bled into damage sites together with the hardener fluid and then polymerized to repair cracks. The system proved to work in the case of monotonic fracture as characterized by the attractive healing effect even below room temperature. As a continuation of our project, the present work is focused on examination of the performance of the epoxy/mercaptan/tertiary amine system in suppression and rehabilitation of fatigue crack in epoxy materials via manual infiltration. Effect of adhesive curing process on fatigue crack propagation was systematically studied. The results are expected to provide a knowledge frame for the subsequent in-situ self-healing that has the practical value for engineering application. Keywords: smart polymers, fracture and fatigue, self-healing, epoxy eXPRESS Polymer Letters Experimental 2.1. Materials and specimen preparationTapered double cantilever beam (TDCB) specimens were cast from the mixture of epoxy resin (EPON 828, diglycidyl ether of bisphenol A, Hexion Specialty Chemicals, USA) and 12.5 pph curing agent (diethylenetriamine, DETA, Shanghai Medical Group Reagent Co., China). The mixture was degassed, poured into a closed silicone rubber mold and cured for 24 h at room temperature, followed by 48 h at 40°C. Table 1 shows the material properties.The healing agent consists of epoxy (1:1 mixture by weight of EPON 828 and diglycidyl ether of resorcin (J-80, Wuxi Resin Factory of Bluestar New Chemical Materials Co., China)) and the hardener (pentaerythritol tetrakis (3-merca...

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Fatigue crack propagation in microcapsule-toughened epoxy

Cited by 161 publications

References 34 publications

Self-healing of fatigue crack in epoxy materials with epoxy/mercaptan system

Self-healing of fatigue crack in epoxy materials with epoxy/mercaptan system

Mechanical Properties of Microcapsules Used in a Self-Healing Polymer

Healing of fatigue crack in epoxy materials with epoxy/mercaptan system via manual infiltration

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