Crack propagation in and fractography of epoxy resins

Yamini, Salim; Young, Robert J.

doi:10.1007/bf00569280

Cited by 75 publications

(18 citation statements)

References 19 publications

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“…Similar behavior in particulate-filled epoxy resins has been reported by Spanoudakis and Young (1984a) and Moloney et al (1983). This behavior has also been reported in unfilled epoxy resins by Yamini and Young (1979) and by Kinloch and Williams (1980). The stress-intensity factor increased as the filler content increased.…”

Section: Discussionsupporting

confidence: 80%

An Investigation into the Fracture Behavior of a Particulate-filled bis-GMA Resin

Davis¹,

Waters

1987

J Dent Res

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Dental composites are being increasingly used to restore occlusal surfaces ofposterior teeth. If these restorations are not to fracture in service, an understanding of their fracture behavior is essential. The fracture parameter used is the stress-intensity factor at crack instability (Kic). This has been calculated by means of the double-torsion test in a mechanical testing machine.The fracture behavior of the composite was studied by varying: the amount offiller (7%, 15%, 26%, and 41% by volume); the surface treatment of the filler (coated or uncoated); the environment (air and water); and the cross-head rate (0.05, 0.5, 5, and 50 mm/min).Fracture was found to occur in either a continuous (stable) or stickslip (unstable) manner. The stick-slip behavior was due to blunting of the crack tip, which was controlled by the yield behavior. When there was no significant blunting, continuous crack growth occurred. An unique relationship was found to exist between the yield stress and the stress-intensity factor for all conditions of testing.

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Section: Discussionsupporting

confidence: 80%

An Investigation into the Fracture Behavior of a Particulate-filled bis-GMA Resin

Davis¹,

Waters

1987

J Dent Res

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“…The epoxy system based on the reaction of the difunctional epoxy monomer diglycidyl ether of bisphenol-A, DGEBA, with aliphatic amines is such an example. The properties of this and other epoxy systems can be varied as a function of the molecular weight of the hardener molecule [7][8][9][10] , by variations in processing conditions [11][12][13] or by the use of different hardener to monomer ratios 8,11,[13][14][15][16][17][18][19][20][21] . This last variable introduces boundary condition (i.e., when a variable like temperature or the amount of monomers is changed).…”

Section: Introductionmentioning

confidence: 99%

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

2003

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An investigation was carried out on the room temperature ageing of off-stoichiometric DGEBA/TETA epoxy formulations. The results obtained show that the epoxy rich mixtures have their inherent brittleness increased by the ageing treatment due to recrystalization of the unreacted epoxy monomers, although homopolymerization could also play a minor role. The initial reaction steps dominated by the amine addition reactions control the macromolecular structure and the mechanical performance of the stoichiometric and near stoichiometric formulation with excess of epoxy monomer. Plasticization due to absorbed -OH results on a significant increase of the deformability of these formulations. The amine rich mixtures have the more stable structures, although plasticization due to moisture absorption from the surrounding environment also produces an increase on the deformability of all, but one, of the formulations investigated. keywords: epoxy resins, ageing, mechanical propertiesoff-stoichiometric mixtures. For the particular system made of the triethylene tetramine, TETA, hardener and the DGEBA monomer the variation of the hardener to monomer ratio promotes strong changes on the mechanical behavior [18][19][20][21] . Of particular interest with respect to these changes is the very sharp increase in the impact strength, when amine rich mixtures were used 21 . The problem of working with off-stoichiometric mixtures is that latent reaction sites could remain on the macromolecular structure developed and under the proper conditions the structure can evolve, resulting in changes on the mechanical performance of the material. Temperature is clearly one external parameter that could cause changes to the system, but, even at room temperature, ageing due to exposure of the epoxy resin to humid environments could also be important [22][23][24] . The changes observed on the mechanical properties when the epoxy monomer to hardener ratio is varied, and the possible changes due to aging, are a direct consequence of the different macromolecular structures that are developed and/or the possible reactions that could occur given a

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“…[4][5][6] Therereactivity of the epoxy group with different comfore, a comprehensive picture of the molecular changes that occur as a function of these pro- …”

Section: Introductionmentioning

confidence: 99%

Thermal diffusivity of an epoxy system as a function of the hardener content

d’Almeida

Cella

Monteiro

et al. 1998

J. Appl. Polym. Sci.

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ABSTRACT:The influence on the thermal diffusivity of the changes induced on the macromolecular network of an epoxy-amine system by different hardener/resin ratios was experimentally investigated. For each hardener/resin ratio, the open photoacoustic cell technique was used to measure the thermal diffusivity. The thermal diffusivity data was correlated with the evolution of the characteristic infrared absorption bands of the epoxy and amine components using a fast Fourier transform spectrometer. The results show a sharp transition in the thermal diffusivity values at the beginning of the amine-rich domain, corresponding to a transformation from a rigid network to an amine saturated deformable structure. It is concluded that the open photoacoustic cell technique can be a useful monitoring tool for structural characterization and molecular evolution during the curing of this kind of system.

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Crack propagation in and fractography of epoxy resins

Cited by 75 publications

References 19 publications

An Investigation into the Fracture Behavior of a Particulate-filled bis-GMA Resin

An Investigation into the Fracture Behavior of a Particulate-filled bis-GMA Resin

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

Thermal diffusivity of an epoxy system as a function of the hardener content

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