Effects of Environmental Conditions on the Behavior of Graphite/epoxy Composites PDF Download

Author: Sang Chel Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 344

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Author: DL. Buchanan
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 11

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The purpose of this research is to experimentally determine the combined influence of frequency and environmental conditions on dynamic behavior of graphite/epoxy composites. The new additions to the data base on dynamic behavior facilitate confident use of these composites in applications.

Author: Christopher C. Pauly
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 64

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Book Description
The increasing acceptance and incorporation of fiber-reinforced polymer matrix composites (PMCs) as engineering construction materials have led many to look to the infrastructure as an application for these versatile materials. One such system is pultruded graphite fiber-reinforced epoxy (graphite/epoxy). Some PMC systems degrade when subjected to environmental conditions (e.g., moisture, stress, UV light, electrochemical polarization). These variables are typically studied either singularly or in series, but in real applications (e.g., aerospace, marine, infrastructure), these materials are subjected to many of these conditions simultaneously. To simulate field conditions, this study investigated the combined effects of an aqueous environment, electrochemical polarization, and applied bending stress on the durability of a pultruded graphite/epoxy composite. The findings indicate that graphite/epoxy composites cannot be assumed to be insensitive to degradation by environmental variables. Further, electrochemical polarization, as might occur with contact with a metal such as a fastener, can accelerate degradation. This damage requires the presence of moisture. Chloride and sulfate concentrations in rain are sufficient to establish an electrolyte within creviced regions, but deicing salts would overtake these as a contributor to conductivity. Further findings may be summarized as follows: 1.) Application of polarization in an aerated 0.6M NaCl environment led to breakdown of the fiber/matrix interface. The high pH environment created during the oxygen reduction reaction was necessary but not sufficient to create this breakdown, as the unpolarized specimen exposed to a pH 13 environment did not degrade. Cathodic polarization as would occur by coupling to steel or aluminum is required. 2.)Application of cathodic polarization did not significantly alter strength. Average measurements of shear strength, however, did decrease with the application of cathodic polarization for 70 and 90 days.

Author: L. W. Rehfield
Publisher:
ISBN:
Category :
Languages : en
Pages : 5

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Author: K. G. Kibler
Publisher:
ISBN:
Category :
Languages : en
Pages : 152

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Experimental and analytical investigations have been conducted to determine the individual and combined effects of temperature and absorbed moisture on the time-dependent mechanical response of unidirectional and cross- plied graphite-epoxy composite. Tensile creep response was measured at room temperature and four elevated temperatures (up to the glass transition region of the materials) for dry specimens and for specimens moisture-saturated at 75% and 95% relative humidity. Results were obtained for two material systems: Narmco T300-5208 and Hercules AS/3502. The stress levels used were demonstrated to be within the range of linear viscoelastic response. Superposition techniques were used to determine compliance master curves from the results for individual temperature and moisture condition, and quasi-elastic conversion was employed to extract relaxation modules behavior. Expansional strains due to temperature and moisture were measured. From measured principal properties, laminate response was predicted using time-stepped elastic analyses for the environments considered. Analytical procedures for transient and nonuniform temperature and moisture conditions were formulated. An analytical method for minimizing residual stresses during cure was developed, and sample results for the present materials are presented. Observations and recommended resulting from these investigations are included in this final report.

Author: George S. Springer
Publisher: CRC Press
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 222

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Author: Konstantinos Peimanidis
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Henry Robert Phelps
Publisher:
ISBN:
Category : Graphite fibers
Languages : en
Pages : 160

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Author: CL. Leung
Publisher:
ISBN:
Category : Composites
Languages : en
Pages : 8

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In a study of T300/934 graphite/epoxy composite, which forms the composite skin of the space shuttle cargo bay doors, the following composite properties were investigated as a function of increasing gamma-radiation exposure dosages: directional moisture absorption/desorption kinetics, glass transition temperatures, interlaminar shear strength and damping peaks (tan ?). Irradiation conditions were: open to atmosphere and vacuum, ambient and high temperature (100°C).

Author: George S. Springer
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 534

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