Fracture energy of an epoxy composite system

Lange, F. F.; Radford, K.C.

doi:10.1007/bf00550091

Cited by 269 publications

(120 citation statements)

References 6 publications

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“…A crack pinning mechanism has been invoked for micrometre-sized glass particles [10,45,46], and also for nanoparticles [18]. This draws parallels to the impediment of the movement of dislocations through metals by particles (dispersion hardening), e.g.…”

Section: Crack Pinningmentioning

confidence: 99%

“…Similarly, Green et al [49] demonstrated pinning with 132 µm diameter particles, but δ tc = 0.3 μm and the diameter of the plastic zone was less than 60 μm (conservative estimates calculated assuming that the yield stress is equal to the quoted fracture stress). Others [10,13,45,46] have invoked pinning though the lack of microscopic evidence makes it difficult to establish whether pinning really occurred. Norman and Robertson [52] observed no bowing lines on the fracture surfaces and discounted crack pinning, finding that off-plane processes dominated the toughening effect.…”

Section: Crack Pinningmentioning

confidence: 99%

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Toughening mechanisms of nanoparticle-modified epoxy polymers

Johnsen

Kinloch

Mohammed

et al. 2007

Polymer

862

576

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An epoxy resin, cured with an anhydride, has been modified by the addition of silica nanoparticles.The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles which were about 20 nm in diameter. Atomic force and electron microscopy showed that the nanoparticles were well dispersed throughout the epoxy matrix. The glass transition temperature was unchanged by the addition of the nanoparticles, but both the modulus and toughness were increased. The measured modulus was compared to theoretical models, and good agreement was found. The fracture energy increased from 100 J/m 2 for the unmodified epoxy to 460 J/m 2 for the epoxy with 13 vol% of nanosilica. The fracture surfaces were inspected using scanning electron and atomic force microscopy, and the results were compared to various toughening mechanisms proposed in the literature. The toughening mechanisms of crack pinning, crack deflection and immobilised polymer were discounted. The microscopy showed evidence of debonding of the nanoparticles and subsequent plastic void growth. A theoretical model of plastic void growth was used to confirm that this mechanism was indeed most likely to be responsible for the increased toughness that was observed due to the addition of the nanoparticles. IntroductionEpoxy polymers are widely used for the matrices of fibre-reinforced composite materials and as adhesives. When cured, epoxies are amorphous and highly-crosslinked (i.e. thermosetting)polymers. This microstructure results in many useful properties for structural engineering applications, such as a high modulus and failure strength, low creep, and good performance at elevated temperatures.However, the structure of such thermosetting polymers also leads to a highly undesirable property in that they are relatively brittle materials, with a poor resistance to crack initiation and growth.Nevertheless, it has been well established for many years that the incorporation of a second microphase of a dispersed rubber, e.g. Hence rigid, inorganic particles have also been used, as these can increase the toughness without affecting the glass transition temperature of the epoxy. Here glass beads or ceramic (e.g. silica or alumina) particles with a diameter of between 4 and 100 μm are typically used, e.g. [9][10][11][12][13][14].However, these relatively large particles also significantly increase the viscosity of the resin, reducing the ease of processing. In addition, due to the size of these particles they are unsuitable for use with infusion processes for the production of fibre composites as they are strained out by the small gaps between the fibres.More recently, a new technology has emerged which holds promise for increasing the mechanical performance of such thermosetting polymers. This is via the addition of a nanophase structure in the polymer, where the nanophase consists of small rigid particles of silica [15][16][17][18]. Such nanoparticle-modified epoxies have been shown to not only increase further the toug...

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Section: Crack Pinningmentioning

confidence: 99%

Section: Crack Pinningmentioning

confidence: 99%

Toughening mechanisms of nanoparticle-modified epoxy polymers

Johnsen

Kinloch

Mohammed

et al. 2007

Polymer

862

576

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“…Lange et al (53)(54)(55) proposed a different toughening mechanism, that is, the crack-pinning mechanism, which is quite different from the mechanisms of crazing, cavitation, or the shear yielding. They observed increased fracture toughness when aluminum trihydrate was added as a fire-retarding filler to epoxy resins.…”

Section: Toughening Mechanismsmentioning

confidence: 99%

Mechanisms of Toughening Thermoset Resins

Huang

Hunston

Kinloch

et al. 1993

Advances in Chemistry

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“…They include the aspect ratio of the filler [5,17], the orientation of the fillers, interfacial interaction and the nature of the failure [5]. From the studies reported [18,24,[28][29][30][31][32][33][34][35][36], it seems that there is a critical particle size, usually in nanoscale, above which there is no effect on Treated Titanium Dioxide Dispersion/Natural Rubber Latex composite modulus. When the particle size is below this critical value, the effect on composite modulus is more significant.…”

Section: Resultsmentioning

confidence: 99%

Mechanical and Morphological Properties of Films Based on Ultrasound Treated Titanium Dioxide Dispersion/Natural Rubber Latex

Ochigbo¹,

Luyt²

2012

CMATERIALS

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Titanium dioxide dispersion was sonicated as an attempt to reduce its particle sizes and thereafter used as fillers in making natural rubber (NR) composite films. Fillers of reduced particle sizes, owing to enhanced surface areas and aspect ratios, usually result in unique property improvements. The reinforcing effects of untreated and sonicated samples of the fillers were, therefore, compared through the measurement of tensile properties of the dry films. Results, however, indicated a monotonic decrease in moduli with filler content, contrary to behaviour due to conventional fillers, but showed improvement in both elongation at break and tensile strength data at low filler concentration (2phr), and thereafter a decrease in the trend. The affinity between the filler and matrix was examined using the composite theory of Einstein. Theoretical prediction of Young's moduli from this was compared against experimental data and it was found that there was certain level of interfacial interaction.

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Fracture energy of an epoxy composite system

Cited by 269 publications

References 6 publications

Toughening mechanisms of nanoparticle-modified epoxy polymers

Toughening mechanisms of nanoparticle-modified epoxy polymers

Mechanisms of Toughening Thermoset Resins

Mechanical and Morphological Properties of Films Based on Ultrasound Treated Titanium Dioxide Dispersion/Natural Rubber Latex

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