Graphene oxide sheets with isocyanate functional groups (GO NCO) were firstly synthesized and functionalized graphene/polyimide (FGS/PI) nanocomposites were subsequently prepared by typical solution casting and thermal imidization. The chemical changes of GO NCO during the preparation of FGS/PI nanocomposites were carefully characterized by Fourier transfer infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the morphology analysis indicated that the FGS were dispersed in the PI matrix and were aligned more orderly with increasing the FGS contents. The tensile strength and the modulus of FGS/PI nanocomposites were significantly increased by 60% with a small quantity of 0.75 wt% FGS incorporated and decreased beyond that dosage. Moreover, the thermogravimetric analysis (TGA) results revealed that the thermal stability of PI was slightly improved by the incorporation of FGS.

Preparation, mechanical and thermal properties of functionalized graphene/polyimide nanocomposites

An application of the analytic network process in multiple criteria material selection

Friction and wear of fiber-reinforced metal—matrix composites

The erosion wear behaviors of unboiled (UB) and boiled eggshells filler reinforced epoxy composites have been characterized. The eggshells epoxy composites have been fabricated using a hand layup technique and the samples have been exposed to different environmental conditions i.e. dry, saline, mineral, kerosene and subzero temperature. To examine the effect of the above mentioned environmental conditions at different impingement angles (30, 45, 60, and 90∘) three different particle velocities (v = 86 m/s, 101 m/s and 119 m/s) were selected for the erosion wear behavior. The highest erosion rate is found at 60∘ impingement angle, which indicates the semi-brittle erosion nature of eggshells epoxy composites. The impingement angle and impact velocity have a notable influence on erosion rate. A fruitful effect of filler addition is observed on the erosion wear rate of composites. The erosion rates of unboiled and boiled eggshells epoxy are compared. The 4 wt% unboiled eggshells filler content shows the highest wear resistance in dry condition. The exposure of composites in different environmental conditions had a negative effect on erosion rate.

Effects of Environmental Conditions on Erosion Wear of Eggshell Particulate Epoxy Composites

The design of critical components for aerospace applications involves a number of conflicting functional requirements: reducing fuel consumption, cost, and weight, while enhancing performance, operability and robustness. As several materials systems and concepts remain competitive, a new approach that couples finite element analysis (FEA) and established multicriteria optimization protocols is developed in this paper. To demonstrate the approach, a prototypical materials selection problem for gas turbine combustor liners is chosen. A set of high temperature materials systems consisting of superalloys and thermal barrier coatings is considered as candidates. A thermomechanical FEA model of the combustor liner is used to numerically predict the response of each material system candidate. The performance of each case is then characterized by considering the material cost, manufacturability, oxidation resistance, damping behavior, thermomechanical properties, and the FEA postprocessed parameters relating to fatigue and creep. Using the obtained performance values as design criteria, an ELECTRE multiple attribute decision-making (MADM) model is employed to rank and classify the alternatives. The optimization model is enhanced by incorporating the relative importance (weighting factors) of the selection criteria, which is determined by multiple designers via a group decision-making process. [DOI: 10.1115/1.4006461]

/pdf/a-combined-finite-element-multiple-criteria-optimization-48urzbqje9.pdf

A Combined Finite Element-Multiple Criteria Optimization Approach for Materials Selection of Gas Turbine Components

Advanced aircraft engine research within NASA Lewis focuses on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

/pdf/polymer-metal-and-ceramic-matrix-composites-for-advanced-1uamc5zntb.pdf

Polymer, metal, and ceramic matrix composites for advanced aircraft engine applications

Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

/pdf/polymer-metal-and-ceramic-matrix-composites-for-advanced-1yfg69ove5.pdf

J. A. Dicarlo

Papers

Polymer, metal, and ceramic matrix composites for advanced aircraft engine applications

Polymer, metal and ceramic matrix composites for advanced aircraft engine applications