Composites: A viable option

While it sounded great to be asked to talk about composites, I found it difficult to select subject areas that would be of real interest. My choice is based on saying some things about where the maturity of the composite aircraft structures is today and what that means in terms of future criteria for application. This focus was the basis for my title selection. The other issue that will be addressed was requested by NASA and focuses on composites structures cost. This fits well with the state-of-the-art interpretations I will discuss first, since the cost issue must be viewed from both the current status and future points of view. The difficulty in presenting something in these areas is not in the subjects themselves but in trying to present a real world viewpoint to an audience of composite experts. So, with recognition of the expertise of the audience, I hope you will see something in this presentation about how to view composite aircraft structure

Durability and damage tolerance of Large Composite Primary Aircraft Structure (LCPAS)

Analysis and testing addressing the key technology areas of durability and damage tolerance were completed for wing surface panels. The wing of a fuel-efficient, 200-passenger commercial transport airplane for 1990 delivery was sized using graphite-epoxy materials. Coupons of various layups used in the wing sizing were tested in tension, compression, and spectrum fatigue with typical fastener penetrations. The compression strength after barely visible impact damage was determined from coupon and structural element tests. One current material system and one toughened system were evaluated by coupon testing. The results of the coupon and element tests were used to design three distinctly different compression panels meeting the strength, stiffness, and damage-tolerance requirements of the upper wing panels. These three concepts were tested with various amounts of damage ranging from barely visible impact to through-penetration. The results of this program provide the key technology data required to assess the durability and damage-tolerance capability or advanced composites for use in commercial aircraft wing panel structure

Optimal Anti-Thrombotic Regimen in Watchman Therapy

Nonvalvular atrial fibrillation is the most common sustained arrythmia and an independent risk factor for stroke. Today, 6 million Americans live with this disease. The current standard of care to prevent thrombus formation are anticoagulants such as warfarin. Left atrial appendage occlusion devices are a recently available alternative to long-term anticoagulation. However, it has been learned that thrombus may form on these devices in the early months after deployment, so short-term antithrombotic therapy is recommended for up to 6 months. To date, there have been no studies to determine the optimal antithrombotic therapy regimen post implant. The present study reviews what is known about antithrombotic therapy and proposes a randomized controlled trial to compare the potential utility of direct oral anticoagulant therapy to the presently recommended strategy using warfarin and dual-antiplatelet therapy. Determining the proper antithrombotic profile for post device-placement patients will reduce complications of atrial fibrillation

A conductor\u27s analysis: The birthday cantatas of Christoph Graupner (1683-1760)

Christoph Graupner (1680-1763), court composer and Kapellmeister for Landgrave Ernst Ludwig of Hessen-Darmstadt, was a prolific and highly regarded composer and an esteemed performer during his lifetime and was a contemporary and colleague of Telemann, Bach, and Handel. The quantity of Graupner’s works number among the highest of Baroque composers, with over 1,800 compositions. Much as his contemporary Johann Sebastian Bach (1685-1750), Graupner and his works were largely forgotten following his death. However, unlike Bach, whose music enjoyed a widespread revival during the early nineteenth century that continues to this day, the life and music of Christoph Graupner has remained largely unknown. From an overview of the research literature pertaining to Christoph Graupner, it is evident that, although largely unknown today, Christoph Graupner’s musical work and reputation was strongly present in Germany during his lifetime, leading many to appreciate that, although he was not a radical innovator, Graupner was an important figure in the combination of contrapuntal and galant style characteristics. The purpose of this document is to investigate a specific segment of Christoph Graupner’s musical output, the birthday cantatas composed for his patron and employer, Landgrave Ernst Ludwig of Hessen-Darmstadt (1667-1739). Graupner’s birthday cantatas display compositional elements indicative of both contrapuntal style, including his use of the fugue, and elements of stile galant, with his melody-centered musical textures, specificity of dynamics, and focus on textural and dynamic contrasts. Specifically, this study examines three birthday cantatas, Groβ sind die Wercke des Herrn (1716), Frolockt laβt frohe Lieder hören (1726), and Danket dem Herrn aller Herren (1737), written by Graupner for Landgrave Ernst Ludwig of Hessen-Darmstadt. This document provides biographical background, analysis, and modern editions of the three birthday cantatas in order to bring recognition to this almost unknown composer and his music, further establishing Christoph Graupner as a vital figure in the incorporation of stile galant

Transition services and their effectiveness

The purpose of this study was to determine if transition services as they are currently performed in a large suburban regional high school district are effective in helping classified students make the transition to the world beyond high school. A review of current literature on transition shows that services vary in scope and effectiveness from state to state and from district to district. Interviews with district personnel reveal no follow-up once a student has left the district through graduation or aging out. A survey instrument was compiled and mailed to 200 former students who were classified while attending school in the district. The survey sought information on the transition conference, help from local, state and private agencies and their feelings regarding the help they received from district personnel. The results of the survey were mixed with the district doing a good job overall and the state needing to improve its help of these young people

A Dynamic Model Investigation of the Effect of a Sharp-Edge Vertical Gust on Blade Periodic Flapping Angles and Bending Moments of a Two-Blade Rotor

A two-blade rotor having a diameter of 4 feet and a solidity of 0.037 was subjected to sharp-edge vertical gusts while being operated at various forward speeds to study the effect of the gusts on the blade periodic bending moments and flapping angles. Variables studied included gust velocity, collective pitch angle, flapping hinge offset, and tip-speed ratio. Dimensionless coefficients are derived for the periodic components of the incremental changes in blade flapping angles and bending moments which arise when a rotor blade penetrates a sharp-edge gust. Mental changes in both the flapping angles and bending moments are essentially proportional to gust velocity, and the coefficients express the ratio of these increments to gust velccity. The results show that the flapping coefficient usually increases with an increase in collective pitch angle, is generally dependent on tip-speed ratio, and is essentially independent of the amount of flapping hinge offset. The bending-moment coefficient is also dependent on collective pitch angle and tip-speed ratio. Expected reductions in bending moments are realized by the use of flapping hinges, and further reductions in bending moments are achieved as the amount of flapping hinge offset is increased. Comparison of the experimental results of this investigation with limited available theoretical results shows substantial agreement but indicates that the assumption that the response of the rotor to a sharp-edge gust is independent of the collective pitch angle prior to gust entry is probably inadequate

Design and analysis issues of integrated control systems for high-speed civil transports

A study was conducted to identify, rank, and define development plans for the critical guidance and control design and analysis issues as related to economically viable and environmentally acceptable high-speed civil transport. The issues were identified in a multistep process. First, pertinent literature on supersonic cruise aircraft was reviewed, and experts were consulted to establish the fundamental characteristics and problems inherent to supersonic cruise aircraft. Next, the advanced technologies and strategies being pursued for the high-speed civil transport were considered to determine any additional unique control problems the transport may have. Finally, existing technologies and methods were examined to determine their capabilities for the design and analysis of high-speed civil transport control systems and to identify the shortcomings and issues. Three priority levels - mandatory, highly beneficial, and desirable - were established. Within each of these levels, the issues were further ranked. Technology development plans for each issue were defined. Each plan contains a task breakdown and schedule

Structural Qualification of Composite Airframes

The development of fundamental approaches for predicting failure and elongation characteristics of fibrous composites are summarized in this document. The research described includes a statistical formulation for individual fiber breakage and fragmentation and clustered fiber breakage, termed macrodefects wherein the aligned composite may represent a structural component such as a reinforcing bar element, a rebar. Experimental work conducted in support of the future exploitation of aligned composite rebar elements is also described. This work discusses the experimental challenges associated with rebar tensile test evaluation and describes initial numerical analyses performed in support of the experimental program