Crack Propagation and Bifurcation in Fiber-Composite Models-II: Hard-Soft-Hard Sequence of Phases

Theocaris, P. S.; Papadopoulos, George Α.

doi:10.1177/073168448600500204

Cited by 17 publications

(6 citation statements)

References 19 publications

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“…Since this difference of moduli affects significantly the quality of adhesion between phases, it is reasonable to accept that the important factor, which provokes any crack branching, is the state of adhesion between the phases in the composites. Similar results were derived in [5,6] where meridional sections of the microstructure of fiber composites were studied. Another important remark is that the mesophase plays a preponderant role in attracting neighbouring cracks, thus forming crack branches and avoiding in this way the total failure of a structure.…”

Section: Discussionsupporting

confidence: 67%

“…Considering homogeneous and non-homogeneous plates subjected to the same loadings, it has been previously shown [1][2][3][4][5][6][7] that the reinforced plates with inclusions or fibers are less sensitive to fracture. This means that inclusions or fibers may be considered working as decelerators for p r o p a g a t i n g cracks, thus delaying the complete failure of the structure.…”

Section: Introductionmentioning

confidence: 99%

“…A great variety of these p h e n o m e n a have been already studied experimentally in [1][2][3][4][5][6][7] in the microstructure of composites by considering blown up equatorial sections of composites and studying crack p r o p a g a t i o n s against n o r m a l or inclined single-interfaces or sequences of such interfaces. Whereas the problem of crack propagation in layered media was only partly studied without considering the important case of delamination [8], the problem of the interaction between a propagating crack and a circular inclusion has as yet not been considered either theoretically or experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Crack bifurcation modes in composite plates under impact

Theocaris

Demakos

1986

Int J Fract

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Cracked plates with bonded elastic circular inclusions inside a matrix were subjected to an impact tensile loading. The influence of the inclusion on the propagation of an initial edge-crack was discussed in this paper. Two types of specimens were tested, that is with hard or soft inclusions surrounded by soft or hard matrices respectively. It has been shown that bi-, or tri-furcations of the propagating crack have persistently occurred at the region of mesophase between matrix and circular inclusions. The phenomenon of splitting of the initial crack was common in both types of specimens, For the definition of the prevailing stress field, the dynamic stress intensity factors were evaluated at different positions of the crack, as well as the crack-velocities along the main crack or its branches during their propagation. It was observed that the crack initiation in soft plates with hard inclusions was followed by the emission of Rayleigh waves, which contributed to the mode of fracture of the composite. Isochromatic patterns were also used to simulate the stress-field of the propagating cracks against the inclusions at distinct time-instants where the propagating crack was frozen at this instant and static photoelastic analysis was applied. These approximations gave satisfactory results with the cracks advancing inside the composite plates.

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Section: Discussionsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crack bifurcation modes in composite plates under impact

Theocaris

Demakos

1986

Int J Fract

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“…Also, the same authors in a forthcoming paper [4] have investigated the influence of the inclusions on the directional stability of propagating cracks, presenting interesting phenomena, such as attraction or repulsion, and kinking of the propagating cracks. In similar papers Theocaris and coworkers [5][6][7][8][9][10][11][12] have investigated the interactions of a crack with meridional sections of fiber-composites in cases of slant, perpendicular, or parallel to the crack axis interfaces.…”

Section: Introductionmentioning

confidence: 97%

Crack Propagation Modes in Particulates: A Study Approaching Reality

Theocaris

Demakos

1988

Journal of Composite Materials

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Cracked composite plates with spherical glass inclusions bonded inside a flexible matrix made of an epoxy polymer were subjected to impact. The effect of the inclusions on an edge crack propagating inside the plate was investigated, as well as the interaction of two skew-parallel edge cracks propagating in the same composite plates. It was found that generally the inclusions repel the cracks in both cases studied, and they are responsible for the bifurcations of the propagating cracks. A crack arrest phenomenon also appeared at the neighborhood of inclusions, which was followed by a subsequent emission backwards of Rayleigh waves. Moreover, the skew-parallel cracks always attracted each other, although the inclusions provoked the cracks to deviate from their initial paths. For the study of crack propagation inside these composite plates the optical method of caustics was used for the evaluation of the crack velocities, as well as the instantaneous values of the dyanmic stress-intensity factor K r (t) and K rr (t) at the crack tips. Interesting results were derived concerning the variation of the velocities and SIFs of the cracks inside particulatefilled plates.

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“…They have extended their study to the magnitude and the variation of the crack propagation velocities during fracture in duplex plates under dynamic loading [14]. Also, Theocaris et al [15,16], have studied the influence of the hard or soft fiber and the mesophase layers in a soft-hard-soft or hard-soft-hard combination of biphase plate subjected to a dynamic tensile load, on the fracture mode and bifurcation process in both phases. Also, theoretical studies on this subject were carried out by Gdoutos et al [17][18][19], Theotokoglou et al [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Stress Analysis at a Bi-Material Interface Crack-tip

Papadopoulos¹

2008

TOMEJ

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Abstract:The optical methods of Caustics, Photoelasticity and Isopachics for the evaluation of the stress intensity factors and the distribution of the principal stresses at a bi-material interface crack-tip, were proposed. The caustics, isochromatic and isopachic fringes are developed from the stress field which results from a stress function X(r, ). When the crack-tip, which is perpendicular to interface, is at the interface of the bi-material, the caustics, isochromatic and isopachic fringes depend on the properties of the two materials. So, the caustic, isochromatic and isopachic fringes are divided into two branches, which present a jump of values at the interface. The shape and size of the two branches of caustics, isochromatic and isopachic fringes depend mainly on the elastic modulus and Poisson's ratio of the two materials. From the caustics the stress intensity factor K I can be calculated, while from the combination of the isochromatic and the isopachic fringes, the principal stresses 1 , 2 can be theoretically and experimentally calculated. The optical evaluation of the stress intensity factors and the distribution of the principal stresses from isochromatic and isopachic fringes is presented. The stress intensity factors and the principal stresses at the bi-material interface crack-tip, were experimentally determined using the caustics and the combination photoelastic and isopachic measurements. The size and shape of the crack-tip caustics, isochromatic and isopachic fringes, at a bi-material interface under static load, were theoretically and experimentally studied.

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Crack Propagation and Bifurcation in Fiber-Composite Models-II: Hard-Soft-Hard Sequence of Phases

Cited by 17 publications

References 19 publications

Crack bifurcation modes in composite plates under impact

Crack bifurcation modes in composite plates under impact

Crack Propagation Modes in Particulates: A Study Approaching Reality

Stress Analysis at a Bi-Material Interface Crack-tip

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