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The work presented in this paper is part of a long-term research program to explore methods for improving bleed air system performance. Another objective of this research is to provide detailed experimental data for the development and validation of simulation tools used in the design and analysis of bleed air systems. A business jet wing was equipped with an inner-liner hot air ice protection system and was extensively instrumented for documenting system thermal performance. The wing was tested at the NASA Glenn Icing Research Tunnel (IRT) for representative in-flight icing conditions. Data obtained include bleed air supply and exhaust flow properties, wing leading edge skin temperatures, temperatures and pressures in the interior passages of the bleed air system, flow properties inside the piccolo tube, photos of run back ice shapes and ice shape traces. Selected experimental results for a warm hold icing condition are presented in this paper.

Some of the methods used for experimental detection and examination of wake vortices are presented. The aim of the article is to provide the reader a brief overview of the available methods. The material is divided into two major sections, one dealing with methods used primarily in the laboratory, and the second part devoted to those used in field operations. Over one hundred articles are cited and briefly discussed.

The coupled influence of material configuration (number of facesheet plies, core density, core thickness) and impact parameters (impact velocity and energy, impactor diameter) on the impact damage resistance characteristics of sandwich composites comprised of carbon-epoxy woven fabric facesheets and Nomex honeycomb cores was investigated using empirically based quadratic response surfaces. The diameter of the planar damage area associated with TTU C-scan measurements and the peak residual facesheet indentation depth were used to describe the extent of internal and detectable surface damage, respectively. Estimates of the size of the planar damage region correlated reasonably well with experimentally determined values. For a fixed set of impact parameters, estimates of the planar damage size and residual facesheet indentation suggest that impact damage development is highly material and lay-up configuration dependent.

During this study, a number of 8.5-inch by 11.5-inch flat honeycomb sandwich panels were inflicted with low energy impact damage, inspected non-destructively, and tested for residual in-plane compressive strength. Each panel had either a 3/8-inch or 3/4-inch low density Nomex honeycomb core, and either 2-ply, 4-ply or 6-ply face sheets. The face sheets were either carbon or Eglass (prepreg) fabric. The panels were either clamped or simply supported in a test fixture during impact from a gravity assisted drop mechanism, and impacted with either a 1-inch or 3-inch diameter spherical indenter. After impact the damage to each panel was characterized by (1) ultrasonic through-transmission to obtain a c-scan representing planar damage area, (2) indentation volume and depth, and finally (3) visual inspection to rate the damage according to a predetermined rating scale. The panels were then tested for in-plane compressive strength.

The work presented here illustrates the wear behavior of CVD diamond coated carbide tools during the machining of carbon fiber-reinforced composites. Cutting experiments were conducted on a CNC milling machine for edge trimming of a 9-mm thick multi-layered carbon fiber-reinforced epoxy laminate in a climb cutting configuration. The effects of feed speed and diamond film thickness on the wear behavior of the coated tools were determined. In addition, characteristics of the worn cutting edge were studied using optical and scanning electron microscopes. It was shown that diamond coated tools generally performed better than the uncoated tools under all conditions. Uniform wear by abrasion of the diamond film, without exposing the substrate, was obtained when cutting at low feed speeds with thicker coatings. At higher feed speeds the wear of the coated tools was characterized by abrasion through the diamond film and exposure and wear of the substrate.

A series of carefully selected tests were used to isolate the coupled influence of various combinations of the number of facesheet plies, impact energies, and impactor diameters on the damage formation and residual strength degradation of sandwich composites due to normal impact. The diameter of the planar damage area associated with Through Transmission Ultrasonic C-scan and the compression after impact measurements were used to describe the extent of the internal damage and residual strength degradation of test panels, respectively. Standard analysis of variance techniques were used to assess the significance of the regression models, individual terms, and the model lack-of-fit. In addition, the inherent variability associated with given types of experimental measurements was evaluated.

Laminated metal-metal composites can have attractive fracture toughness properties; they also offer potentially good fatigue performance. These attributes are reviewed and prospects for improvement discussed. Weak interlaminar bonds are seen to be important, while quite thin layers seem to be most promising for laminates of higher strength materials. The experimental program utilized 0.033 in (0.84 mm) thick laminae of 7075-T6 aluminum alloy, adhesively bonded. Eight-layer composites were compared with solid sheets of nearly the same total metal thickness. Both fracture toughness and fatigue properties were determined. Kc values of more than double the KIc for this alloy were observed in the laminates, while fatigue performance as indicated by comparative S-N curves was found to be slightly improved.

Drilling is one of the most widely applied manufacturing operations. Millions of holes are drilled today in manufacturing industries especially in aerospace industry where high quality holes are essential. Rejection and rework rate of the products because of the bad hole is quite high. In this research graphite/honeycomb composite material and aluminum sheet metal has been used. The results show that drill geometry, speed and feed rate have substantial effects on the hole quality and also there was gradual variation of the thrust and lateral forces with feed rates.

Composites are finding more and more applications in the aircraft industry. Drilling good quality holes is a major challenge for the manufacturing industry. The major factors which have an effect on hole quality are cutting parameters like speed and feedrate, machine rigidity, tool material, workpiece material, and tool geometry. The hole quality was studied by measuring the hole diameter and visually observing other parameters like shape and fiber breakout. Force analysis indicates that thrust increases with an increase in feedrate. Speed does not seem to have a very significant effect on thrust. The tool geometry plays a very important role in fiber pullout.