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Relationship of Graphite-Polyimide Composites to Galvanic Processes
Abstract
The possibility of galvanic action between graphite composites and metals has long been recognized. Recently, at General Dynamics Fort Worth Division, it was discovered that imide-linked
resins can degrade under certain laboratory conditions involving the galvanic process. The
galvanic coupling was found to cause hydroxyl ions to be formed at the gaphite cathode, hence
attacking the O-C-N bond of the polyimide ring structure. Degradation was found ro initiate at
exposed graphite sites at salt water/fuel or salt water/stagnant air interfaces. The phenomenon was
found to occur in bismaleimides (BMI), condensation polyimides, triazines, and blends thereof.
Standard galvanic protection schemes were demonstrated to be effective in preventing degradation,
particularly when proper treatment of the composite was provided.
Note: Since this was the first time polymer degradation (corrosion) by glavanic action was mentioned in the literature, that "plastics can corrode" these results have been referred to as "faudree effect" by workers in the aerospace industry.
Supplementary resource (1)
... Titanium alloys, on the other hand, were first developed for the aerospace industry [7] and have since been utilized for jet engine components and airframe structure due to their high strength, stiffness, toughness, fatigue, and excellent resistance to corrosion [8] when coupled with CFRPs [9]. In addition, Ti alloys have the advantage of maintaining mechanical properties at high operating temperatures and can be used for structures requiring heavy loads such as wing-fuselage connections and landing gear [8]. ...
A literature review of up-to-date methods to strengthen Ti/carbon-fiber-reinforced polymer (CFRP) hybrid joints is given. However, there are little or no studies on Ti/CFRP joints by carbon fiber plug insert, which takes advantage of the extremely high surface adhesion area of ~6 μm CFs. Therefore, we cover the current status and review our previously published results developing hybrid joints by a CF plug insert with spot-welded Ti half-lengths to enhance the safety levels of aircraft fan blades. A thermoset Ti/CF/epoxy joint exhibited an ultimate tensile strength (UTS) of 283 MPa when calculated according to the rule of mixtures (RM) for the CF cross-section portion. With concern for the environment, thermoplastic polymers (TPs) allowed recyclability. However, a drawback is easy CF pull-out from difficult-to-adhere TPs due to insufficient contact sites. Therefore, research on a novel method of homogeneous low voltage electron beam irradiation (HLEBI) to activate a bare CF half-length prior to dipping in a TP resin was reviewed and showed that the UTS by the RM of Ti/EBCF/acrylonitrile butadiene styrene (ABS) and Ti/EBCF/polycarbonate (PC) joints increased 154% (from 55 to 140 MPa) and 829% (from 30 to 195 MPa), respectively, over the untreated sample. The optimum 0.30 MGy HLEBI prevented CF pull-out by apparently growing crystallites into the TP around the CF circumference, raising the UTS amount closer to that of epoxy.
... Thermal decomposition chamber receives heat and uses the heat to break complex molecular structures to simple compounds. Even polymers degrade above 250 o C temperature based on their nature at the same time it can also be used to convert wet garbage to dry garbage by dehydration technique which again can be subjected to combustion chamber [4]. Gases released from the combustion chamber are dissolved in base saturated water. ...
Thee elements of this document contains method of designing and design aspects to perform adaptive waste management. This method, adaptive waste management emphasizes on treating all types of domestic and municipal wastes at cheaper and lesser stages to remove physical, chemical and biological contaminants by using a single process in all 3 states of matter solid, liquid and gaseous except thermostats. Adaptive waste management process is bypassing of 4 various techniques to degrade waste into a single stage process. In order to perform adaptive waste management process certain aspects of design and manufacturing are considered in this article. Aspects such as strength, structure and operating thermal range, thermodynamic cycles are stated in this document.
Smart protection of metallic materials is currently a hot topic in mitigation of corrosion of metallic structures, and promises reduction in both economic and environmental costs. Degradation of carbon-reinforced composite materials and CFRP-Metal joints is a serious issue in high-performance weight-optimized structures employed in the aeronautical and automobile industries. Since both carbon-reinforced composite materials and CFRP-Metal joints are ubiquitous in these critical industries, there is a need to develop strategies for smart protection of such complex multi-material systems. In this article, the current state of art/practice in protection of carbon-reinforced composite materials and CFRP-Metal joints is reviewed, the theoretical basis, intricacies and limitation of current practice (in protection of carbon-reinforced composite materials and CFRP-Metal joints) highlighted, distinction made between protection of materials and smart protection of materials, and the need for smart protection of carbon-reinforced composite materials and CFRP-Metal joints are emphasized. In addition, the background for smart protection of carbon-reinforced composite materials and CFRP-Metal joints is laid, and drawing from literature and results from our own research efforts perspectives on critical factors to be considered, and plausible strategies for smart protection of carbon-reinforced composite materials and CFRP-Metal joints is provided.
One of the most important fields of research dealing with the use of carbon-, basalt-, and glass-fiber composites in the civil construction industry is their behavior under various chemical exposure conditions. Fiber-reinforced-polymer composites used as internal and external reinforcement in various structural applications can be subjected to widely differing pH situations. This study investigated the chemical durability of various carbon, basalt and glass fibers. The fibers were immersed in four types of solutions with acid, saline, alkaline, and deionized-water conditioning schemes. The fiber mass loss and surface damage along with changes due to chemical reactions were observed through weight-loss measurements and scanning electron microscopy. A criterion was developed to characterize the performance of fibers as very good, good, fair, and poor. This methodology can also be used by manufacturers as a quick quality-control tool for evaluating the chemical resistance of different fibers prior to large-volume production. The results reveal that the carbon fibers exhibited higher chemical resistance than the basalt and glass fibers based on weight loss and evidence of chemical reactions. Moreover, the determination of the fiber chemical composition before and after conditioning in acid and alkaline solutions clearly shows that the E-glass fibers, which are known to contain boron, were very sensitive to chemical corrosion. The ECR-glass fibers showed excellent chemical durability, even better than the basalt fibers.
The aim of this work is the study of the electrochemical and mechanical behaviour of stainless steel (SS304) adhesively bonded with carbon nanotube (CNT)-reinforced epoxies to either SS304 or carbon-reinforced composites substrates. For metal to metal (MtM) joints, the shear strength of nano-reinforced adhesives was studied using single lap shear specimen geometries. The lap shear strength was improved by almost 50% and the highest shear strength appeared for 0.6% CNT weight content in the adhesive. The metal to composite joint performed altogether better compared to the MtM joint, although the CNT inclusion had an adverse effect on the lap shear strength attributed to the physical property change of the epoxy. Although the incorporation of CNTs was found to increase the galvanic effect, it also enhanced corrosion protection, as the modified adhesives exhibited increased resistance to uniform corrosion and localised corrosion and prevented the electrolyte from reaching the substrate.
In materials strategy, the Department of the Navy is the first to consider the development of novel anti-corrosion inhibitors. Thus we proposed to develop novel corrosion inhibitors based on polymer metallocomplex composite materials. These new materials can cut off the electron transfer path via the polymer metallocomplexes. Bipyridine-based polymerizable ligand monomers were synthesized starting from 4,5-diazatluoren-9-one (1). The copolymers of the polymerizable methacrylate-type monomer with styrene, methyl methacrylate, and butyl methacrylate have strong blue-light- emitting properties. Amphiphilic tris(2,2'-bipyridine)ruthenium-cored star polymers of polystyrene and poly(N-isopropylacrvlannide) were found to self-assemble into core-shell micelles in which the ruthenium ions are located on the interface between core and shell. The amphiphilic star-shaped metallopolymer with longer PNIPAM blocks formed micro-sized aggregates at high concentration To prepare ligand-endfunctionalizedd polymers, we also synthesized ligand-functionalized initiators. We also synthesized the nanoparticles of zeolite Y (of various chemical compositions) using various techniques such as the addition of organic additives to conventional zeolite Y synthesis mixtures to suppress zeolite Y crystal growth; nanoporous slilcate host materials of up to 30 nm pore diameter, using poly (alkylene oxide) copolymers, which when removed will yield a mesoporus material; and investigated the zeolite Y/Nannnroas composite materials as hosts for corrosion inhibitors.
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