Mixed-Mode Fracture of Graphite/Epoxy Composites: Fracture Strength

Morris, D. H.; Hahn, H. T.

doi:10.1177/002199837701100201

Cited by 43 publications

(5 citation statements)

References 8 publications

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“…The characteristic distances appearing in the models are assumed to be material properties. The popularity of these models is evidenced by the number of researchers using them [44][45][46][47][48][49][50]. Pipes et.…”

Section: Failure Modelsmentioning

confidence: 99%

Elastic Properties and Fracture Behavior of Graphite/Polyimide Composites at Extreme Temperatures

Garber¹,

Morris

Everett

1982

Composites for Extreme Environments

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The influence of elevated and cryogenic temperatures on the elastic moduli and fracture strengths of several Celion 6000/PMR-15 laminates was measured. Tests were run at −157, 24 (room temperature), and 316°C (−250, 75, and 600°F). Both unnotched and notched laminates were tested. Several failure criteria, developed to predict the uniaxial fracture strength of epoxy laminates, were used to predict the fracture strength of polyimide laminates. Lamina elastic moduli were measured at each temperature by testing unnotched [0]s, [90]s, and [±45]2s laminates. The measured values were used with classical laminate theory to predict the elastic constants in [0/45/90/−45]s, [0/45/90/−45]2s, [45/0/−45/0]s, and [45/90/−45/90]s laminates. With few exceptions, the predictions agreed with the moduli measured experimentally. As for the ultimate tensile strength, although the 8-ply and 16-ply quasi-isotropic laminates were about equally strong at elevated temperature, their respective strengths diverged at the lower temperatures. The 8-ply laminates lost strength as the temperature decreased, whereas the 16-ply laminates became stronger. The notched laminates had layups of [±45]2s, [0/45/90/−45]s, and [45/0/−45/0]s. The measured moduli, the ultimate strengths, and the point stress or average stress criterion of Nuismer and Whitney were combined to calculate the characteristic lengths associated with each criterion. Characteristic lengths were compared to determine the effect of temperature.

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Section: Failure Modelsmentioning

confidence: 99%

Elastic Properties and Fracture Behavior of Graphite/Polyimide Composites at Extreme Temperatures

Garber¹,

Morris

Everett

1982

Composites for Extreme Environments

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“…However, the model has been extended to be used for notched laminates with finite geometry by introducing the finite width cor- [25,26]. The critical Mode I stress intensity factor Ke for an unnotched laminate with infinite width, in which an inherent flaw of length 2co is present, is expressed as where 6o is the unnotched tensile strength.…”

Section: Inherent Flaw Modelmentioning

confidence: 99%

Tensile Fracture of Laminates with Cracks

Aronsson

Bäcklund

1986

Journal of Composite Materials

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In this paper a method, called the Damage Zone Model (DZM), is used for predicting strength of composites with through-the-thickness cracks. The DZM is based on the two fundamental parameters unnotched tensile strength (σ 0 ) and apparent fracture energy (G* c ). The damage zone, developed at a notch in the composite, is modelled as a crack with cohesive forces acting on the crack surfaces. Redistribution of stresses and change in stiffness is accounted for in the model. For comparison, strengths are also calculated by semi-empirical methods such as the inherent flaw and the point stress criteria.Experimental results for three point bend (TPB), single edge notch (SEN) and compact tension (CT) quasi-isotropic carbon/epoxy specimens are presented. Some results for specimens made from randomly oriented short glass fiber/polyester specimens are also discussed. The damage zone model is shown to accurately predict fracture load, loaddeformation behaviour and damage zone sizes in these types of laminates.

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“…Although use of the average stress failure criterion has previously been restricted to uniaxial tensile loadings [1][2][3][4][5] , the extension of its use to compressive failure seems plausible since the rationale for its use in tension (ultimate failure results when localized damage occurs over a sufficiently large region) would appear to be equally applicable to compressive loadings. However, it is not expected that the same value of the characteristic length, aot, used in tensile loading cases would be applicable to compressive failure predictions.…”

Section: Average Stress Criterion In Compressionmentioning

confidence: 99%

Applications of the Average Stress Failure Criterion: Part II — Compression

Nuismer

Labor

1979

Journal of Composite Materials

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Results are presented for the compressive fracture strength of several Gr/Ep (AS/3501-5) laminates containing countersunk holes with both loaded and unloaded fasteners in place. Finite element stress analyses are presented which approximate the countersink geometry and the elastic contact problem. The average stress failure criterion is successfully used to predict the observed strengths in all cases considered. SCOPE N A NUMBER of recent papers [1, 2, 3, 4, 5] , the average stress failure criterion was found to result in reasonably accurate strength predictions for composite laminates containing cutouts and subjected to uniaxial tensile loads. Despite the fact that the rationale behind the average stress failure criterion would appear to be equally applicable to compressive failure, it appears that no attempts at predicting compressive fracture strengths of laminates containing cutouts have been made using this criterion.In the present paper, the results of a series of uniaxial compressive tests are presented for graphite/epoxy laminates containing countersunk fastener holes in

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Mixed-Mode Fracture of Graphite/Epoxy Composites: Fracture Strength

Cited by 43 publications

References 8 publications

Elastic Properties and Fracture Behavior of Graphite/Polyimide Composites at Extreme Temperatures

Elastic Properties and Fracture Behavior of Graphite/Polyimide Composites at Extreme Temperatures

Tensile Fracture of Laminates with Cracks

Applications of the Average Stress Failure Criterion: Part II — Compression

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