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Author: Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
The objectives of the CRADA are to: Confirm that fiber-resin adhesion is responsible for the observed poor shear properties; Determine the mechanism(s) responsible for poor adhesion between carbon fibers and epoxy resins after e-beam curing; Develop and evaluate resin systems and fiber treatments to improve the properties of e-beam cured, carbon-fiber-reinforced composites; and Develop refined methods for processing e-beam cured, carbon-fiber-reinforced composites.
Author: Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
The objectives of the CRADA are to: Confirm that fiber-resin adhesion is responsible for the observed poor shear properties; Determine the mechanism(s) responsible for poor adhesion between carbon fibers and epoxy resins after e-beam curing; Develop and evaluate resin systems and fiber treatments to improve the properties of e-beam cured, carbon-fiber-reinforced composites; and Develop refined methods for processing e-beam cured, carbon-fiber-reinforced composites.
Author: C. J. Janke Publisher: ISBN: Category : Languages : en Pages :
Book Description
Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly because of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly manage the large project team and properly address the various technical tasks, the CRADA team was organized into integrated project teams (IPT's) with each team focused on specific research areas. Early in the project, the end user partners developed ''exit criteria'', recorded in Appendix B, against which the project's success was to be judged. The project team made several important discoveries. A number of fiber coatings or treatments were developed that improved fiber-matrix adhesion by 40% or more, according to microdebond testing. The effects of dose-time and temperature-time profiles during the cure were investigated, and it was determined that fiber-matrix adhesion is relatively insensitive to the irradiation procedure, but can be elevated appreciably by thermal postcuring. Electron beam curable resin properties were improved substantially, with 80% increase in electron beam 798 resin toughness, and {approx}25% and 50% improvement, respectively, in ultimate tensile strength and ultimate tensile strain vs. earlier generation electron beam curable resins. Additionally, a new resin electron beam 800E was developed with generally good properties, and a very notable 120% improvement in transverse composite tensile strength vs. earlier generation electron beam cured carbon fiber reinforced epoxies. Chemical kinetics studies showed that reaction pathways can be affected by the irradiation parameters, although no consequential effects on material properties have been noted to date. Preliminary thermal kinetics models were developed to predict degree of cure vs. irradiation and thermal parameters. These models are continually being refined and validated. Despite the aforementioned impressive accomplishments, the project team did not fully realize the project objectives. The best methods for improving adhesion were combined with the improved electron beam 3K resin to make prepreg and uni-directional test laminates from which composite properties could be determined. Nevertheless, only minor improvements in the composite shear strength, and moderate improvements in the transverse tensile strength, were achieved. The project team was not satisfied with the laminate quality achieved, and low quality (specifically, high void fraction) laminates will compromise the composite properties. There were several problems with the prepregging and fabrication, many of them related to the use of new fiber treatments.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The objective of this project was to characterize the properties of the resin and the fiber-resin interface in electron beam cured materials by evaluating several structural and processingparameters. The Oak Ridge National Laboratory (ORNL) has recently determined that theinterlaminar shear strength properties of electron beam cured composites were 19-28% lowerthan for autoclave cured composites. Low interlaminar shear strength is widely acknowledged asthe key barrier to the successfid acceptance and implementation of electron beam curedcomposites in industry. In this project we found that simple resin modification and process improvements areunlikely to substantially improve the interlaminar shear strength properties of electron beamcured composites. However, sizings and coatings were shown to improve these properties andthere appears to be significant potential for further improvement. In this work we determinedthat the application of epoxy-based, electron beam compatible sizings or coatings onto surface-treated, unsized carbon fibers improved the composite interlaminar shear strength by as much as55% compared to composites fabricated from surface-treated, unsized carbon fibers and 11 YOcompared to composites made from surface-treated, GP sized carbon fibers. This work has identified many promising pathways for increasing the interlaminar shearstrength of electron beam cured composites. As a result of these promising developments wehave recently submitted a U.S. Department of Energy-Energy Research (DOE-ER) sponsoredLaboratory Technical Research-Cooperative Research and Development Agreement (LTR-CRADA) proposal entitled, "Interracial Properties of Electron Beam Cured Composites", tocontinue this work. If funded, ORNL will lead a 3-year, $2.6 million effort involving eightindustrial partners, NASA-Langley, and the U.S. Air Force. The principal objective of thisCRADA is to significantly improve the interracial properties of carbon-fiber-reinforcedcomposites beyond the current state-of-the art electron beam cured composites for use in severalDOE, DoD, and industrial applications. In addition, several papers from this LaboratoryDirector's Research and Development (LDRD) project will be submitted to the Society for theAdvancement of Materials and Process Engineering for oral presentations and publications.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
The recently completed Department of Energy (DOE) and industry sponsored Cooperative Research and Development Agreement (CRADA) entitled, ''Electron Beam Curing of Polymer Matrix Composites, '' determined that the interlaminar shear strength properties of the best electron beam cured IM7/epoxy composites were 19-28% lower than autoclave cured IM7/epoxy composites (i.e. IM7/977-2 and IM7/977-3). Low interlaminar shear strength is widely acknowledged as the key barrier to the successful acceptance and implementation of electron beam cured composites in the aircraft/aerospace industry. The objective of this work was to improve the interlaminar shear strength properties of electron beam cured composites by formulating and evaluating several different fiber sizings or coating materials. The researchers have recently achieved some promising results by having discovered that the application of epoxy-based, electron beam compatible sizings or coatings onto surface-treated, unsized IM7 carbon fibers improved the composite interlaminar shear strength properties by as much as 55% versus composites fabricated from surface-treated, unsized IM7 fibers. In addition, by applying these same epoxy-based sizings or coatings onto surface-treated, unsized IM7 fibers it was possible to achieve an 11% increase in the composite interlaminar shear strength compared to composites made from surface-treated, GP-sized IM7 fibers. Work is continuing in this area of research to further improve these properties.
Author: Keizo Makuuchi Publisher: John Wiley & Sons ISBN: 0470587695 Category : Science Languages : en Pages : 448
Book Description
This text examines the effect of radiation on polymers and the versatility of its industrial applications. By helping readers understand and solve problems associated with radiation processing of polymers, it serves as an important reference and fills a gap in the literature. Radiation processing can significantly improve important properties of polymers, however, there are still misconceptions about processing polymers by using ionizing radiation. This book explains the radiation processing of polymeric materials used in many industrial products including cars, airplanes, computers, and TVs. It even addresses emerging "green" issues like biomaterials and hydrogels.
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Author: Linas Repecka
Author: Keizo Makuuchi