Scaling Effects in the Impact Response of Graphite-Epoxy Composite Beams

Jackson, Karen E.; Fasanella, Edwin L.

doi:10.4271/891014

Cited by 10 publications

(17 citation statements)

References 5 publications

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“…It is perhaps worth noting that, with the exception of one previously reported case of cracked specimens of the same material system [11], there have been no other reports of cracked virgin laminates. For example, Highsmith and Reifsnider [12] studied the relationship of transverse cracks and applied load for (00/9003)s E-glass epoxy specimens.…”

mentioning

confidence: 95%

“…Material properties used for strength and stiffness prediction. These values were reported in [11]. The coefficients of thermal expansion were not supplied: AS4/3501 values reported in [9] were used.…”

Section: Suggested Further Workmentioning

confidence: 99%

“…Material properties used for strength and stiffness prediction. Values were reported in [11]. Table 7.…”

Section: List Of Tablesmentioning

confidence: 99%

“…Damage was recorded on M5 Kodak X-ray film. Since the same specimen 11 was used in a load increment/damage evaluation procedure, it was assumed that the penetrant solution had no effect upon the fracture characteristics of the epoxy. To validate this assumption, tests for a given specimen were carried out in as short a period as possible to reduce the amount of penetrant absorbed by the matrix.…”

Section: Damage Evaluationmentioning

confidence: 99%

“…Sf= SmO·12 -0.12)..) (11) where Sf and Sm are the strengths of the full scale and model specimens respectively. Combining…”

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confidence: 99%

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Strength scaling in fiber composites

Kellas

Morton

1991

32nd Structures, Structural Dynamics, and Materials Conference

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A research program has been initiated to study and isolate the factors responsible for scale effects in the tensile strength of graphite/epoxy composite laminates.Four lay-ups, (±30° n/9002n)s, (±45° n/O° n/90° n)s, (90° nlO° n/90° n/O° n)s, and (±45° n/±45 ° n)s, have been chosen with appropriate stacking sequences so as to highlight individual and interacting failure modes. Four scale sizes have been selected for investigation including full scale size, 3/4, 2/4, and 1/4, with n equal to 4, 3,2, and 1, respectively. The full scale specimen size was 32 plies thick as compared to 24, 16, and 8 plies for the 3/4, 2/4, and 1/4 specimen sizes respectively.Results were obtained in the form of tensile strength, Stress/strain curves and damage development. Problems associated with strength degradation with increasing specimen size have been isolated and discussed. Inconsistencies associated with strain measurements have also been identified. Enhanced X-ray radiography was employed for damage evaluation, following step loading.It has been shown that fiber dominated lay-ups were less sensitive to scaling effects compared to the matrix dominated lay-ups. Further, it has been shown that fabrication induced damage was partly responsible for the observed behavior.Extrapolation to the full scale strength was attempted by means of three basic methods: a Weibull statistics based model, a fracture mechanics based model, and a combination model involving the previous two models in conjunction with a failure criterion. The predictive performance of each one of these models has been assessed and their applicability to the present problem has been discussed.

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mentioning

confidence: 95%

Section: Suggested Further Workmentioning

confidence: 99%

“…Material properties used for strength and stiffness prediction. Values were reported in [11]. Table 7.…”

Section: List Of Tablesmentioning

confidence: 99%

Section: Damage Evaluationmentioning

confidence: 99%

“…Sf= SmO·12 -0.12)..) (11) where Sf and Sm are the strengths of the full scale and model specimens respectively. Combining…”

mentioning

confidence: 99%

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Strength scaling in fiber composites

Kellas

Morton

1991

32nd Structures, Structural Dynamics, and Materials Conference

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Structural Similitude and Scaling Laws for Plates and Shells: A Review

Simitses

Starnes

Rezaeepazhand

2001

Advances in the Mechanics of Plates and Shells

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IntroductionThis paper deals with the development and use of scaled-down models in order to predict the structural behavior of large prototypes. The concept is fully described and examples are presented which demonstrate its appficability to beam-plates, plates and cylindrical shells of laminated cons_ction. The concept is based on the use of field equations, which govern the response behavior of both the small model as well as the large prototype. The conditions under which the experimental data of a small model can be used to predict the behavior of a large prototype are called scaling laws or similarity conditions and the term that best describes the process is structural similitude. Moreover, since the term scaling is used to describe the effect of size on strength characteristics of materials, a discussion is included which should clarify the difference between "scaling law" and "size effect".Finally, a historical review of all published work in the broad area of stnmtural similitude is presented for completeness.• Aircraft and spacecraft comprise the class of aerospace structures that require efficiency and wisdom in design, sophistication and accuracy in analysis and numerous and careful experimental evaluations of components and prototype, in order to achieve the necessary system reliability, performance and safety.Preliminary and/or concept design entails the assemblage of system mission requirements, system expected performance and identification of components and their connections as well as of manufacturing and system assembly techniques. This is accomplished through experience based on previous similar designs, and through the possible use of models to simulate the entire system characteristics.Detail design is heavily dependent on information and concepts derived from the previous step. This information identifies critical design areas 'which need sophisticated analyses, and design and redesign procedures to achieve the expected component performance.This step may require several independent analysis models, which, in many instances, require component testing.The last step in the design process, before going to production, is the verification of the design. This step necessitates the production of large components and prototypes in order to test component and system analytical predictions and verify strength and peffom3ance requirements under the worst loading conditions that the system is expected to encounter in service.

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Size Effect on Flexural Strength of Fiber-Composite Laminates

Bažant

Zhou

Novák

et al. 2004

Journal of Engineering Materials and Technology

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The size effect on the flexural strength (or modulus of rupture) of fiber-polymer laminate beams failing at fracture initiation is analyzed. A generalized energetic-statistical size effect law recently developed on the basis of a probabilistic nonlocal theory is introduced. This law represents asymptotic matching of three limits: (1) the power-law size effect of the classical Weibull theory, approached for infinite structure size; (2) the deterministic-energetic size effect law based on the deterministic nonlocal theory, approached for vanishing structure size; and (3) approach to the same law at any structure size when the Weibull modulus tends to infinity. The limited test data that exist are used to verify this formula and examine the closeness of fit. The results show that the new energetic-statistical size effect theory can match the existing flexural strength data better than the classical statistical Weibull theory, and that the optimum size effect fits with Weibull theory are incompatible with a realistic coefficient of variation of scatter in strength tests of various types of laminates. As for the energetic-statistical theory, its support remains entirely theoretical because the existing test data do not reveal any improvement of fit over its special case, the purely energetic theory—probably because the size range of the data is not broad enough or the scatter is too high, or both.

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Scaling Effects in the Impact Response of Graphite-Epoxy Composite Beams

Cited by 10 publications

References 5 publications

Strength scaling in fiber composites

Strength scaling in fiber composites

Structural Similitude and Scaling Laws for Plates and Shells: A Review

Size Effect on Flexural Strength of Fiber-Composite Laminates

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