Crack-face grain interlocking/bridging of a polycrystalline graphite: The role in mixed mode fracture

Li, M.; Tsujimura, Motoh; Sakai, Mototsugu

doi:10.1016/s0008-6223(99)00026-3

Cited by 32 publications

(20 citation statements)

References 25 publications

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“…Li et al [35] reported on "crack-face interlocking/bridging of polycrystalline graphite: The role in mixed mode fracture". In their study of isotropic fine grained graphite, using the single edge notched beam (SENB), and for mixed modes a pre-cracked SENB referred to as a single-edge pre-cracked beam Li et al [35] et al concluded that bridging/interlocking in the crack wake region reduced the stress intensity factor K I and K II , leading to a toughening of a cracked body.…”

Section: Introductionmentioning

confidence: 99%

The shear fracture toughness, K, of graphite

Burchell

Erdman

2016

Carbon

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The critical shear stress intensity factor, K IIc , herein referred to as the shear fracture toughness, K IIc (MPa√m), of two grades of graphite are reported. The range of specimen volumes was selected to elucidate any specimen size effect, but smaller volume specimen tests were largely unsuccessful, shear failure did not occur between the notches as expected. This was probably due to the specimen geometry causing the shear fracture stress to exceed the compressive failure stress. In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce the specimen's ligament length. Additionally, we added the collection of Acoustic Emission (AE) during testing to assist with the identification of the shear fracture load. The means of K IIc from large specimens for PCEA and NBG-18 are 2.26 MPa√m with an SD of 0.37 MPa√m and 2.20 MPa√m with an SD of 0.53 MPa√m, respectively. The value of K IIc for both graphite grades was similar, although the scatter was large. In this work we found the ratio of K IIc /K Ic ≈1.6.

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Section: Introductionmentioning

confidence: 99%

The shear fracture toughness, K, of graphite

Burchell

Erdman

2016

Carbon

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“…Este valor así obtenido es sólo un valor aparente de la tenacidad del material, ya que no se tuvo en cuenta el crecimiento estable de las grietas antes de alcanzarse carga máxima (bien documentado tanto para el grafito [1][2][3][4][5] como para los compuestos C/C [5,[6][7]), ni la influencia del radio del fondo de la entalla (≈ 90 µm). Sin embargo, este último factor puede ser obviado cuando la longitud de los defectos presentes en el material son del orden del radio de la entalla tal y como documentó Li et al [8].…”

Section: Tenacidad Y Micromecanismos De Fracturaunclassified

Comportamiento mecánico y estudio in situ de la evolución del daño en el grafito y en un compuesto C/C a 77 y a 300 K

Salazar¹,

Pastor²,

Llorca³

2002

Bol. Soc. Esp. Ceram. Vidr.

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Comportamiento mecánico y estudio in situ de la evolución del daño en el grafito y en un compuesto C/C a 77 y a 300 K A. SALAZAR, J. Y. PASTOR, J. LLORCA Departamento de Ciencia de Materiales. Universidad Politécnica de Madrid. E.T.S.I. de Caminos.Ciudad Universitaria, E-28040-Madrid.En este trabajo se han evaluado las propiedades mecánicas a 77 y a 300 K de dos grafitos policristalinos con microestructuras muy diferentes y de un compuesto C/C. Se realizaron ensayos de flexión en tres puntos y de tenacidad, y en éstos últi-mos se midió in situ la iniciación y la evolución del daño en el fondo de la entalla con un microscopio de larga distancia focal. Los resultados obtenidos muestran que las temperaturas criogénicas no afectan el comportamiento mecánico de los compuestos de carbono estudiados. Además, la porosidad presente en los grafitos es el mecanismo de rotura dominante mientras que en el material compuesto, la intercara débil entre matriz y haz de fibras detiene y desvía las grietas nucleadas en la matriz, presentando el mejor comportamiento mecánico. Palabras clave: grafito, material compuesto C/C, micromecanismos de rotura, criogenía, propiedades mecánicas.Mechanical behavior and in situ study of the damage evolution at 77 and at 300 K of graphite and C/C composites.The mechanical properties at 77 K and at 300 K were determined in two polycristalline graphites with different microstructures and in a C/C composite. The flexure strength and the fracture toughness were evaluated and the micromechanic failure was studied in situ with a long distance microscope. The results obtained showed that the mechanical properties of these carbon materials are not affected by the cryogenic temperatures. The porosity is the main responsible of the mechanical failure in the graphites while in the composite, the matrix/yarn interface deflect the crack nucleated in the mattrix, presenting the best mechanical behavior.

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“…Yamauchi et al, 2000Yamauchi et al, , 2001Wang & Liu, 2008;Etter et al, 2004;Yum & You, 2001;Wosu et al, 2005;Jurf & Pipes, 1982;Latella & Liu, 2006;Sato et al, 1978Sato et al, , 1981Knibbs, 1967;Allard et al, 1991;Burchell, 1996;Lomakin et al, 1975;Losty, 1962;Greenstreet, 1968;Greenstreet et al, 1969;Aliha et al, 2015a;Nemeth, 2011;Mostafavi et al, , 2013aMostafavi et al, , 2013b. Especially Awaji and Sato (1978), Li et al (1999), Yamauchi et al (2000Yamauchi et al ( , 2001, and Shi et al (2008) conducted a large number of tests to determine fracture toughness under mode I and mixed mode I+II with different cracked specimens. Recently, the crack nucleation in poly-granular graphite has been investigated by Marrow (2011, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The wide spread of this material in the composites field such as graphite/epoxy composites, has also pushed some researchers to study the fracture resistance of graphite under pure mode I and mixed mode I+II loading conditions (Yamauchi et al, 2000(Yamauchi et al, , 2001Li et al, 1999). Other important aspects such as crack growth, the stress intensity factors, and also fracture toughness have been investigated by Latella and Liu (2006) through the arc-discharge method.…”

Section: Introductionmentioning

confidence: 99%

Review of local strain energy density theory for the fracture assessment of V-notches under mixed mode loading

Ayatollahi¹,

Berto²,

Campagnolo³

et al. 2017

10.5267/j.esm

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The present work summarizes some recent experimental, theoretical and numerical results on brittle fracture of isostatic polycrystalline graphite. The analyses have been carried out on Vnotched samples under mixed mode (I+II), torsion and compression loading, considering various combinations of the notch tip radius, opening angle and notch tilt angle. The static strength of the considered specimens is assessed through an approach based on the strain energy density averaged over a control volume. The center of the control volume is located on the notch edge, where the principal stress reaches its maximum value. The correct orientation is obtained by a rigid rotation of the crescent-shaped volume while the size depends on the fracture toughness and the ultimate strength of the material. This methodology has been already used in the literature to analyze U-and V-shaped notches subject to mode I loading with very good results and advantages with respect to classic approaches. The results reported in this new work show, also under mixed mode loading conditions, good agreement between experimental data and theoretical predictions.

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Crack-face grain interlocking/bridging of a polycrystalline graphite: The role in mixed mode fracture

Cited by 32 publications

References 25 publications

The shear fracture toughness, K, of graphite

The shear fracture toughness, K, of graphite

Comportamiento mecánico y estudio in situ de la evolución del daño en el grafito y en un compuesto C/C a 77 y a 300 K

Review of local strain energy density theory for the fracture assessment of V-notches under mixed mode loading

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