On cracks in rectilinearly anisotropic bodies

Sih, G. C.; Paris, Paul C.; Irwin, G. R.

doi:10.1007/bf00186854

Cited by 1,212 publications

(454 citation statements)

References 6 publications

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“…In addition, J-integral values are not constant along the crack length, with the finiteelement model being focused on the maximum value attained at the symmetry plane (point A in figures 3a and 4c). The stress intensity factor at point A was determined from the J-integral by using the following Irwin's relation for anisotropic solids derived by Sih et al [9] J = a 11 · a 22 2…”

Section: Resultsmentioning

confidence: 99%

Strength and toughness of structural fibres for composite material reinforcement

Herráez

Fernández

Lopes

et al. 2016

Phil. Trans. R. Soc. A.

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The characterization of the strength and fracture toughness of three common structural fibres, E-glass, AS4 carbon and Kevlar KM2, is presented in this work. The notched specimens were prepared by means of selective carving of individual fibres by means of the focused ion beam. A straight-fronted edge notch was introduced in a plane perpendicular to the fibre axis, with the relative notch depth being a 0 / D ≈0.1 and the notch radius at the tip approximately 50 nm. The selection of the appropriate beam current during milling operations was performed to avoid to as much as possible any microstructural changes owing to ion impingement. Both notched and un-notched fibres were submitted to uniaxial tensile tests up to failure. The strength of the un-notched fibres was characterized in terms of the Weibull statistics, whereas the residual strength of the notched fibres was used to determine their apparent toughness. To this end, the stress intensity factor of a fronted edge crack was computed by means of the finite-element method for different crack lengths. The experimental results agreed with those reported in the literature for polyacrylonitrile-based carbon fibres obtained by using similar techniques. After mechanical testing, the fracture surface of the fibres was analysed to ascertain the failure mechanisms. It was found that AS4 carbon and E-glass fibres presented the lower toughness with fracture surfaces perpendicular to the fibre axis, emanating from the notch tip. The fractured region of Kevlar KM2 fibres extended along the fibre and showed large permanent deformation, which explains their higher degree of toughness when compared with carbon and glass fibres. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

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Section: Resultsmentioning

confidence: 99%

Strength and toughness of structural fibres for composite material reinforcement

Herráez

Fernández

Lopes

et al. 2016

Phil. Trans. R. Soc. A.

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“…Here we see that, as noted in [63,65,66], the growth of small cracks essentially conforms to a Paris-like equation and is largely R-ratio independent. Noting that for metals and orthotropic materials [25] that G is proportional to K 2 , we see that plotting the data given in Figure 2 as a function of ∆(K 2 ) transforms Figure 2 from a clear and well-ordered figure to a near chaotic plot, see Figure 3. It also makes it appear that for a given value of the crack driving force, which in this instance is ∆(K 2 ), tests performed at R = 0.1 are more severe than tests at R = 0.7 even though the later will have a greater K max value.…”

Section: Alternative Fracture Mechanics Based Approachesmentioning

confidence: 90%

“…Whereas Sih, Paris and Irwin [25] were the first to derive expressions for the energy releaserate associated with a crack in a composite structure, the work of Sih and Chen [56] was the first to show that cracking in the matrix material could be captured via the strain-energy density, W, defined as:…”

Section: Alternative Fracture Mechanics Based Approachesmentioning

confidence: 99%

Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

Jones

Kinloch

Michopoulos

et al. 2017

Composite Structures

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The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction by the Federal Aviation Administration (FAA) of a 'slow growth' approach to the certification of composites has further focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under fatigue loads. Specific attention is given to the test and data-reduction procedures required to determine a 'valid' rate of fatigue crack growth (FCG), da/dN, versus the range of the energy release-rate, ΔG, (or the maximum energy release-rate, G max , in a cycle) relationship (a) to characterise and compare different types of composites, and (b) for designing and lifing in-service composite structures. Now, fibre-bridging may occur behind the tip of the advancing delamination and may cause very significant retardation of the FCG rate. Such retardation effects cannot usually be avoided when using the Mode I double-cantilever beam test to ascertain experimentally the fatigue behaviour of composites, so that a means of estimating a valid (i.e. ideally a 'retardation-free' or, at least, a very low-retardation) relationship is needed. The present paper presents a novel methodology, that is based on a variant of the Hartman-Schijve equation, to ascertain a valid, 'retardation-free', upper-bound FCG rate curves.

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“…A more formal treatment of the problem, for instance by applying the fracture mechanics analysis of Sih, Paris & Irwin (1965) S~-1 P /kr (kg cm ) for diamond (Howes 1959(Howes , 1962 (See text. )…”

Section: Discussionmentioning

confidence: 99%

Hertzian Fracture in Single Crystals with the Diamond Structure

Lawn

1968

Journal of Applied Physics

165

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Extension of an earlier theory of Hertzian fracture in brittle isotropic materials (Frank & Lawn 1967) is here made to include the case of brittle single crystals.A criterion is first proposed for predicting the path of a crack through an inhomogeneously stressed crystal in terms of the surface energy anisotropy of the crystal and the stresses prior to fracture occurring. This criterion is then applied to determine the geometry of cracks formed in the Hertzian stress field in crystals having the diamond structure. The computed crack geometries agree well with observation.

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On cracks in rectilinearly anisotropic bodies

Cited by 1,212 publications

References 6 publications

Strength and toughness of structural fibres for composite material reinforcement

Strength and toughness of structural fibres for composite material reinforcement

Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

Hertzian Fracture in Single Crystals with the Diamond Structure

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