Advanced materials research for long-haul aircraft turbine engines
The status of research efforts to apply low to intermediate temperature composite materials and advanced high temperature materials to engine components is reviewed. Emerging materials technologies and their potential benefits to aircraft gas turbines were emphasized. The problems were identified, and the general state of the technology for near term use was assessed.
Study of the costs and benefits of composite materials in advanced turbofan engines
Composite component designs were developed for a number of applicable engine parts and functions. The cost and weight of each detail component was determined and its effect on the total engine cost to the aircraft manufacturer was ascertained. The economic benefits of engine or nacelle composite or eutectic turbine alloy substitutions was then calculated. Two time periods of engine certification were considered for this investigation, namely 1979 and 1985. Two methods of applying composites to these engines were employed. The first method just considered replacing an existing metal part with a composite part with no other change to the engine. The other method involved major engine redesign so that more efficient composite designs could be employed. Utilization of polymeric composites wherever payoffs were available indicated that a total improvement in Direct Operating Cost (DOC) of 2.82 to 4.64 percent, depending on the engine considered, could be attained. In addition, the percent fuel saving ranged from 1.91 to 3.53 percent. The advantages of using advanced materials in the turbine are more difficult to quantify but could go as high as an improvement in DOC of 2.33 percent and a fuel savings of 2.62 percent. Typically, based on a fleet of one hundred aircraft, a percent savings in DOC represents a savings of four million dollars per year and a percent of fuel savings equals 23,000 cu m (7,000,000 gallons) per year.
The Effects of Certain Polymers on Tensile strength and Tension Relaxation of Wet Web
The trend in papermaking has been towards lower basis weights, decreased amounts of softwood kraft pulp and an increased use of fillers and recycled fibers. All these changes tend to result in lower strengths of both wet and dry web. To maintain necessary strength in the papers, a greater quantity of strength additives is often required. The effect of different polymers on the dry paper strength has been widely studied and the action of mechanism of different polymers is quite well known. There is much less information of their effect on wet web properties, and especially on the tensile strength and relaxation characteristics. In this laboratory scale study, the effects of adding different polymers by spraying on wet web tensile and relaxation characteristics at high strain rate were examined. The sprayings were done on wet paper sheets before wet pressing. The results showed that spraying of polymers significantly improves wet and dry paper tensile strength without any increase in dry paper density. The effect of different polymers on wet web mechanical properties was characteristic for each polymer. Carboxymethyl cellulose (CMC) and chitosan improved wet web tensile strength at dryness levels higher than 55%, while polyvinyl alcohol (PVA) improved wet web tensile strength also at lower dryness levels. The most prominent increase in dry and wet web tensile strength was obtained by sequential application of oppositely charged polymers. However, the relative increase of tensile strength was significantly higher for the wet web (80% increase) than for the dry paper (35% increase) compared to the reference without added polymer. Also the mode of polymer addition had a significant effect on wet web tensile strength. Despite a significant increase in the wet web strength, only minor effects on the residual tension (tension after 0.475 s relaxation) was observed. Based on this result, it was concluded that spray addition of the polymers used in this study increased molecular level interactions between fibers but had no effect on the fiber network activation.