Compressive Behavior of Frame-Stiffened Composite Panels

New technologies are being developed under NASA's Environmentally Responsible Aviation (ERA) Program aimed at reducing fuel burn and emissions in large commercial aircraft. A Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept is being developed which offers advantages over traditional metallic structure. In this concept a stitched carbon-epoxy material system is employed with the potential for reducing the weight and cost of transport aircraft structure by eliminating fasteners and producing a more damage tolerant design. In addition, by adding unidirectional carbon rods to the top of stiffeners and minimizing the interference between the sandwich frames and the rod-stiffened stringers, the panel becomes more structurally efficient. This document describes the results of experimentation on a PRSEUS panel in which the frames are loaded in unidirectional compression beyond the local buckling of the skin of a Hybrid Wing Body (HWB) aircraft. A comparison with analytical predictions and the relationship between these test results and the global aircraft design is presented

Design, Analysis and Testing of a PRSEUS Pressure Cube to Investigate Assembly Joints

Due to its potential to significantly increase fuel efficiency, the current focus of NASA's Environmentally Responsible Aviation Program is the hybrid wing body (HWB) aircraft. Due to the complex load condition that exists in HWB structure, as compared to traditional aircraft configurations, light-weight, cost-effective and manufacturable structural concepts are required to enable the HWB. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept is one such structural concept. A building block approach for technology development of the PRSEUS concept is being conducted. As part of this approach, a PRSEUS pressure cube was developed as a risk reduction test article to examine a new integral cap joint concept. This paper describes the design, analysis and testing of the PRSEUS pressure cube test article. The pressure cube was required to withstand a 2P, 18.4 psi, overpressure load requirement. The pristine pressure cube was tested to 2.2P with no catastrophic failure. After the addition of barely visible impact damage, the cube was pressure loaded to 48 psi where catastrophic failure occurred, meeting the scale-up requirement. Comparison of pretest and posttest analyses with the cube test response agree well, and indicate that current analysis methods can be used to accurately analyze PRSEUS structure for initial failure response

PRSEUS Acoustic Panel Fabrication

This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program

Damage Arresting Composites for Shaped Vehicles - Phase II Final Report

This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration. In addition to the analytical studies, a three specimen test program was also completed to assess the concept under axial tension loading, axial compression loading, and internal pressure loading

MOTION-COMPENSATED VIDEO CODING TECHNIQUES

International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, NevadaThe ever-increasing demands of the modern telemetry system for the transmission of high resolution digital video data at primary and sub-primary bit rates necessitate the employment of efficient motion-compensated video coding algorithms. This paper reviews the current status of motion compensation techniques. The two major classes of motion estimation methods currently being used for predictive coding of time varying images: block matching and pel-recursive algorithms are treated in thorough detail. Examples of practical video coding systems using motion compensated compression are exhibited. Recent advances in the VLSI technology have made it possible to fit the entire circuitry required for a motion compensation algorithm onto a single chip.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

AN OVERVIEW OF VIDEO CODING TECHNIQUES

International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaAn update review of the advances in data compression of video signals is presented with the focus being on schemes best suited for telemetry applications. Several important features for image compression are addressed which serve as guidelines in the design of data compression schemes for custom specific applications. In accordance with this list of distinguishing attributes, a classification of existing compression algorithms is attempted. Two major classes of encoding techniques, transform and predictive encoding, are treated in thorough detail.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

B2-sequences and the distinct distance constant

AbstractA sequence of positive integers 1 < α1 < α2 < … with the property that all differences αj − αi, i < j are distinct is called a B2-sequence. Denote by DDC (distinct difference constant) the maximum over all possible B2-sequences of the sum ∑(1αi). Previously known upper and lower bounds for the DDC are 2.1597 < DDC < 2.374. We have estimated the following sharper bounds on DDC: 2.1600383 < DDC < 2.2473. We have further proved that any B2-sequence which achieves the maximum reciprocal sum must start with the terms 1,2,4