Concepts for bridged Mode ii delamination cracks

Massabò, Roberta; Cox, Brian N.

doi:10.1016/s0022-5096(98)00107-0

Cited by 104 publications

(68 citation statements)

References 33 publications

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“…In both cases, the calculated G increases slightly in the initial crack growth region less than 20 mm, then it settles back to the expected values. These numerical results manifest the ACK limit as discussed in [10,11]. When the crack growth exceeds this limit, the critical shear stress criterion can be accurately applied to simulate crack growth.…”

Section: Model Verificationsupporting

confidence: 65%

“…However, in doing so, it could be difficult to obtain an analytical closed form solution. Same theories and similar approaches have been applied by Massabo et al [10,11] to examine a bridged mode II delamination in detail from an analytical and conceptual viewpoint. For example, they have discussed two limiting crack configurations: the small-scale bridging limit when the bridging zone size is constant and much smaller than the crack length; and the ACK limit when the critical applied shear stress is independent of crack length.…”

Section: Introductionmentioning

confidence: 99%

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Mode II delamination toughness of z-pinned laminates

Yan

Liu

Mai

2004

Composites Science and Technology

101

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Mode II delamination toughness of z-pin reinforced composite laminates is investigated using the finite element (FE) method. The z-pin pullout process is simulated by the deformation and breakage of non-linear springs. A critical shear stress criterion based on linear elastic fracture mechanics is used to simulate crack growth in an end-notched flexure (ENF) beam made of z-pinned laminates. The mode II toughness is quantified by the potential energy release rate calculated using the contour integral method. This FE model is verified for an unpinned ENF composite beam. Numerical results obtained indicate that z-pins can significantly increase the mode II delamination toughness of composite laminate. The effects of design variables on the toughness enhancement of z-pinned laminates are also studied, which provide an important technological base and useful data to optimise and improve the zpinning technique.

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Section: Model Verificationsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Mode II delamination toughness of z-pinned laminates

Yan

Liu

Mai

2004

Composites Science and Technology

101

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“…Again, equation (3b), which accounts for structural depth, generally provides the best correlation with numerical results, but it is necessary to apply M = 0.5 to gain a close match. Previous work by Massabo and Cox [22] has shown that the equivalent mode II modulus in the characteristic length equation for slender bodies, E' II,slender , takes the same value as the longitudinal modulus, E 11 , and is influenced by no other elastic moduli. However, the cohesive zone length in the 3ENF specimen is seen to increase from a value of 3mm for a shear modulus, G 13 lengths for mode II are significantly longer.…”

Section: (Insert Figure 13)mentioning

confidence: 96%

Cohesive zone length in numerical simulations of composite delamination

Harper¹,

Hallett²

2008

Engineering Fracture Mechanics

435

287

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Abstract:Accurate analysis of composite delamination using interface elements relies on having sufficient elements within a softening region known as the cohesive zone ahead of a crack tip. The present study highlights the limitations of existing formulae used to predict numerical cohesive zone length and demonstrates modifications necessary for improved accuracy. Clarification is also provided regarding the minimum number of interface elements within the cohesive zone. Finally, appropriate values of numerical interfacial strength are examined. The results presented will aid the application of mesh design techniques that both preserve numerical accuracy, whilst minimising computational expense. Where applicable, subscripts I, II and m are used to denote properties under mode I, mode II and mixed mode loading respectively. Keywords

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“…Delamination arrest can persist under increasing load and failure then occurs by some other mechanism [14]. Fracture predictions must be based on large scale bridging models, in which the effect of the mixed mode tractions applied to the fracture surfaces by the through-thickness reinforcement is considered explicitly [17]. The use of K-formulae assuming an unbridged crack to deduce a fracture toughness value is inadequate.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of crack bridging by composite and metallic rods

Cartié

Cox

Fleck

2004

Composites Part A: Applied Science and Manufacturing

143

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Experiments are reported that explore the mechanics of single pins or rods that bridge a delamination crack in a miniature model specimen. The effects of material and geometrical parameters are determined by varying the angle of the rod, its material, and the material in which it is embedded. Different tests represent mode I and mode II loading, with respect to a pre-existing delamination crack.Many observed mechanisms are similar to those previously reported for stitches and in limited studies on rods. They include debonding and sliding of the rod relative to the substrate, lateral deflection of the rod into the substrate (when mode II is present), rod pullout, and rod rupture.Sliding in mode I can be explained by assuming that pullout is resisted by uniform friction, which has a modest value (, 1 -20 MPa). However, when mode II loading is present and the rod deflects laterally, a more complicated friction behaviour is suggested. Peak load occurs well after the whole rod has begun to slide out of the specimen, implying that the pullout process is stable in mode II to large displacements. This, together with the high values observed for the peak loads and displacements suggest the presence of an enhanced friction zone (snubbing effect) extending over the segment of the rod that has been laterally deflected by mode II loading. This zone can grow under increasing shear displacements even after the whole rod begins to slide, leading to increasing shear loads (stable pullout). Various characteristics of the pullout experiments are consistent with this model. q

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Concepts for bridged Mode ii delamination cracks

Cited by 104 publications

References 33 publications

Mode II delamination toughness of z-pinned laminates

Mode II delamination toughness of z-pinned laminates

Cohesive zone length in numerical simulations of composite delamination

Mechanisms of crack bridging by composite and metallic rods

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