The Effect of Graphite Fiber Properties on Microcracking Due to Thermal Cycling of Epoxy-Cyanate Matrix Laminates PDF Download
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Author: N. Jayaraman
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 15
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Book Description
Graphite-fiber-reinforced polymer composite materials have become prime candidates for space structures. The high specific strengths and stiffnesses obtainable with these materials and the ability to design them with a near-zero coefficient of thermal expansion provide a flexibility that is virtually unmatched. However, microcracks resulting from thermal cycling can lead to drastic property changes of the composites. Specimens of five composite materials, each with the same epoxy-cyanate blend matrix and reinforced with different graphite fibers, were subjected to a simulated spacecraft thermal cycling environment to determine the effects of fiber physical properties on the resulting microcrack behavior. The lay-up for each material was [0/45/90/-45]s with a nominal ply thickness of 0.0125 cm (0.005 in). The specimens were cycled between -157°C (-250°F) and +121°C (+250°F) up to 500 times. They were examined at a magnification of x400 at different thermal cycle intervals for microcracks. It was found that although the maximum crack density varied with the ply lay-up angle, it did not vary much with fiber type. However, the fiber type had a strong influence on the rate of microcrack development. This behavior was found to be best described by fitting a hyperbolic function to the microcrack density as a function of the number of thermal cycles.
Author: N. Jayaraman
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 15
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Book Description
Graphite-fiber-reinforced polymer composite materials have become prime candidates for space structures. The high specific strengths and stiffnesses obtainable with these materials and the ability to design them with a near-zero coefficient of thermal expansion provide a flexibility that is virtually unmatched. However, microcracks resulting from thermal cycling can lead to drastic property changes of the composites. Specimens of five composite materials, each with the same epoxy-cyanate blend matrix and reinforced with different graphite fibers, were subjected to a simulated spacecraft thermal cycling environment to determine the effects of fiber physical properties on the resulting microcrack behavior. The lay-up for each material was [0/45/90/-45]s with a nominal ply thickness of 0.0125 cm (0.005 in). The specimens were cycled between -157°C (-250°F) and +121°C (+250°F) up to 500 times. They were examined at a magnification of x400 at different thermal cycle intervals for microcracks. It was found that although the maximum crack density varied with the ply lay-up angle, it did not vary much with fiber type. However, the fiber type had a strong influence on the rate of microcrack development. This behavior was found to be best described by fitting a hyperbolic function to the microcrack density as a function of the number of thermal cycles.
Author: Roderick H. Martin
Publisher: ASTM International
ISBN: 0803120125
Category : Composite materials
Languages : en
Pages : 517
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1044
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Author:
Publisher:
ISBN:
Category : Ceramic materials
Languages : en
Pages : 274
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Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 708
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Author: JL. Camahort
Publisher:
ISBN:
Category : Coefficient of thermal expansion
Languages : en
Pages : 13
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Book Description
Graphite/epoxy (Gr/E) composites have attractive properties--low density, high stiffness, and a low coefficient of thermal expansion (CTE)--that make them prime candidates for many spacecraft applications. The effects of a thermal cycling environment on the dimensional stability and microstructural integrity of Gr/E composites were evaluated. Severe microcracking was found in several high-modulus fiber (HMS)-reinforced 350°F-cure epoxy resin systems after exposure to 25 thermal cycles between the temperature of liquid nitrogen (-320°F) and that of boiling water (+212°F). A hybrid system combining Thornel-300 (T-300) fabric and HMS tape exhibited fewer microcracks, with the fabric acting as a crack stopper. Of the material systems investigated, a 250°F-cure system, HMS/CE 339, was found to be the most resistant to microcracking. The effects of thermal cycling on the microyield strength (MYS) and CTE of several near-zero expansion Gr/E composites were also studied.
Author: Myer Kutz
Publisher: William Andrew
ISBN: 0323524737
Category : Technology & Engineering
Languages : en
Pages : 686
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Book Description
The Handbook of Environmental Degradation of Materials, Third Edition, explains how to measure, analyze and control environmental degradation for a wide range of industrial materials, including metals, polymers, ceramics, concrete, wood and textiles exposed to environmental factors, such as weather, seawater, and fire. This updated edition divides the material into four new sections, Analysis and Testing, Types of Degradation, Protective Measures and Surface Engineering, then concluding with Case Studies. New chapters include topics on Hydrogen Permeation and Hydrogen Induced Cracking, Weathering of Plastics, the Environmental Degradation of Ceramics and Advanced Materials, Antimicrobial Layers, Coatings, and the Corrosion of Pipes in Drinking Water Systems. Expert contributors to this book provide a wealth of insider knowledge and engineering expertise that complements their explanations and advice. Case Studies from areas such as pipelines, tankers, packaging and chemical processing equipment ensure that the reader understands the practical measures that can be put in place to save money, lives and the environment. - Introduces the reader to the effects of environmental degradation on a wide range of materials, including metals, plastics, concrete, wood and textiles - Describes the kind of degradation that effects each material and how best to protect it - Includes case studies that show how organizations, from small consulting firms, to corporate giants design and manufacture products that are more resistant to environmental effects
Author: James M. Larsen
Publisher: Wiley-TMS
ISBN:
Category : Science
Languages : en
Pages : 384
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Book Description
The proceedings arose from a three-day symposium on Materials Damage Prognosis, which was held as part of the Materials Science and Technology.
Author: L Subhadra Burugula
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages :
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Book Description
Wind Turbine blade icing is a serious problem in cold climates, which leads to production losses, failure of the blade, ice throw etc. To eliminate production downtime associated with icing of wind turbine blades, a structurally integrated, carbon fiber based wind turbine blade heating system has been proposed. The de-icing of the blades, where the carbon fiber element is heated which results in a temperature gradient across the blade which may compromise the structural properties of the material. This is explained by the uneven thermal expansion of the different components in the composite (blade) material. Due to the micro-cracking in the composite material it leads to deterioration of the material which further leads to failure. There is a need to investigate the effects of thermal cycling on the structural properties of the composite material. The two main parts of this thesis include the thermal cycling of the CF reinforced glass epoxy laminate samples and Flexural testing on the thermal cycled samples. Thermal cycling is performed on CF reinforced glass epoxy laminate samples with a range of -18 °C to 4 °C with a hold time of 10 minutes for each heating/cooling cycle. A set of 6 samples were taken for each thermal cycle and ran 0, 50, 100, 200 thermal cycles. Temperatures of the samples were recorded using the computer program as well as pictures were taken using a thermal camera; from this data it shows that there is a considerable temperature difference between the carbon fiber and side thermocouples. To study the effects of this temperature gradient on the flexural properties of the laminate, on all the samples three point bending tests (following ASTM standards) are performed and examined for any change in the properties with the increase in the number of thermal cycles. Test results showed that there is very little decrease in the ultimate stress when numbers of thermal cycles were increased from 0 to 200; this decrease is not significant to affect or degrade the material properties of the sample. There might be an effect on material properties when thermal cycling is done in higher levels with more thermal cycling temperature range.
Author: Paul E. McMahon
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 184
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Book Description
