Application of an instrumental and computational approach for improving the vibration behavior of structural panels using a lightweight multilayer composite

Producción CientíficaThis work presents a hybrid (experimental-computational) application for improving the vibration behavior of structural components using a lightweight multilayer composite. The vibration behavior of a flat steel plate has been improved by the gluing of a lightweight composite formed by a core of polyurethane foam and two paper mats placed on its faces. This composite enables the natural frequencies to be increased and the modal density of the plate to be reduced, moving about the natural frequencies of the plate out of excitation range, thereby improving the vibration behavior of the plate. A specific experimental model for measuring the Operating Deflection Shape (ODS) has been developed, which enables an evaluation of the goodness of the natural frequencies obtained with the computational model simulated by the finite element method (FEM). The model of composite + flat steel plate determined by FEM was used to conduct parametric study, and the most influential factors for 1st, 2nd and 3rd mode were identified using a multifactor analysis of variance (Multifactor-ANOVA). The presented results can be easily particularized for other cases, as it may be used in cycles of continuous improvement as well as in the product development at the material, piece, and complete-system levels

Workshop Proceedings: Optical Systems Technology for Space Astrophysics in the 21st Century, volume 3

A technology development program, Astrotech 21, is being proposed by NASA to enable the launching of the next generation of space astrophysical observatories during the years 1995-2015. Astrotech 21 is being planned and will ultimately be implemented jointly by the Astrophysics Division of the Office of Space Science and Applications and the Space Directorate of the Office of Aeronautics and Space Technology. A summary of the Astrotech 21 Optical Systems Technology Workshop is presented. The goal of the workshop was to identify areas of development within advanced optical systems that require technology advances in order to meet the science goals of the Astrotech 21 mission set, and to recommend a coherent development program to achieve the required capabilities

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

NASA Composite Materials Development: Lessons Learned and Future Challenges

Composite materials have emerged as the materials of choice for increasing the performance and reducing the weight and cost of military, general aviation, and transport aircraft and space launch vehicles. Major advancements have been made in the ability to design, fabricate, and analyze large complex aerospace structures. The recent efforts by Boeing and Airbus to incorporate composite into primary load carrying structures of large commercial transports and to certify the airworthiness of these structures is evidence of the significant advancements made in understanding and use of these materials in real world aircraft. NASA has been engaged in research on composites since the late 1960 s and has worked to address many development issues with these materials in an effort to ensure safety, improve performance, and improve affordability of air travel for the public good. This research has ranged from synthesis of advanced resin chemistries to development of mathematical analyses tools to reliably predict the response of built-up structures under combined load conditions. The lessons learned from this research are highlighted with specific examples to illustrate the problems encountered and solutions to these problems. Examples include specific technologies related to environmental effects, processing science, fabrication technologies, nondestructive inspection, damage tolerance, micromechanics, structural mechanics, and residual life prediction. The current state of the technology is reviewed and key issues requiring additional research identified. Also, grand challenges to be solved for expanded use of composites in aero structures are identified

Index to 1983 NASA Tech Briefs, volume 8, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1983 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Aeronautics Technology Possibilities for 2000: Report of a workshop

The potential of aeronautical research and technology (R&T) development, which could provide the basis for facility planning and long range guidance of R&T programs and could establish justification for support of aeronautical research and technology was studied. The projections served specific purposes: (1) to provide a base for research and future facilities needed to support the projected technologies, and development advanced vehicles; (2) to provide insight on the possible state of the art in aeronautical technology by the year 2000 for civil and military planners of air vehicles and systems. Topics discussed include: aerodynamics; propulsion; structures; materials; guidance, navigation and control; computer and information technology; human factors; and systems integration

Research and Technology Report: 1997

This volume highlights the most significant results from research and development projects sponsored through NASA's Office of Equal Opportunity Programs, Minority University Research and Education Division, in collaboration with Headquarters Program Offices, during Academic Year 1996-97 and Summer 1996. It includes the work of major multidisciplinary research groups, such as those sponsored under NASA's University Research Centers at Minority Institutions and Institutional Research Awards programs, as well as that of individual principal investigators sponsored under the Faculty Awards for Research or other MUREP programs. It encompasses contributions from 863 students and 388 faculty-level researchers at institutions eligible to compete for MUREP funding, including: Historically Black Colleges and Universities (HBCU), Hispanic-Serving Institutions (HSI), Tribal Colleges and Universities (TCU), and accredited minority colleges or universities with a 50 percent or greater underrepresented minority student enrollment. It stands as a testimony to NASA's response to Executive Orders 12876, 12900, and 13021, which mandate increased Federal support to these classes of institutions. We firmly believe that maintaining America's leadership in aerospace and related areas depends on fully utilizing the talents available at the Nation's minority universities

Dinamičko mehanička svojstva hibridnih nanokompozitnih materijala

Predmet istraživanja ove doktorske disertacije pripada oblasti nanomateijala i nanotehnogija koja je u trendu savremenih istraživanja. Posebno su intenzivna istraživanja u oblasti polimernih nanokompozita gde tradicionalno slabe strane polimera (niske vrednosti parametara mehaničke čvrstoće i loša termostabilnost) se značajno poboljšavaju primenom malog udela nano punioca i ojačanja uz neznatan porast gustine. Razvijena je metoda dizajniranja strukture nanokompozitnih balističkih materijala sa gledišta poboljšanja njihovih svojstava otpornosti pri udarima visoke energije. Proučeni su uslovi dobijanja laminarnih kompozitnih materijala p-aramid/poli (vinil butiral). Poli (vinil butiralni) sloj nanošen je u obliku disperzije poli (vinil butirala) i nano čestica SiOR2R u etil-alkoholu, pri čemu su korišćene modifikovane i nemodifikovane čestice SiOR2 Rsa vezujućim agensom-AMEO silanom. Na taj nači je utvrđen veliki značaj modifikacije nano čestica SiOR2R sa silanima na mehanička, termička i antibalistička svojstva dobijenih hibridnih nanokompozitnih materijala. Savremena istraživanja u ovoj oblasti usmerena su u pronalaženju mehanizama zaustavljanja rasta prsline modifikovanjem strukture na nano nivou što je i predmet ove doktorske disertacije. Proučavanja u okviru ove disertacije bila su usmerena na istraživanja mehanizama apsorpcije energije u nanokompozitima pri udarnim opterećenjima visoke energije i ponašanje nano čestica kao konstituenata u strukturi hibridnih kompozitnih materijala. Sinteza ovih nanokompozitnih materijala izvršiće se primenom koloidnih suspenzija koje se karakterišu ekstremnim porastom viskoznosti pri velikim brzinama smicanja kojima su izloženi pri udarnim naprezanjima. Originalnost ideje se ogleda što je princip hibridizacije primenjen na izradu laminatnih balističkih ploča sa laminama koje su različito nanomodifikovane a samim tim i sa različitim svojstvima. Značaj ove ideje je što različito nanomodifikovane lamine omogućavaju izradu funkcionalno gradijentnih kompozitnih materijla od nano do mikro nivoa. Ciljevi ove disertacije su višestruki: 1) proučavanje mehanizama procesiranja nano prahova različitih oksida u različitim disperzionim sredstvima prema klasičnim metodama i savremenim metodama modifikovanja površine čestica; 2) eksperimentalna istraživanje uticaja procesnih uslova brizganja i toplog presovanja hibridnih nonokompozita sa tkaninama od aramidnih vlakana sa različitim udelom modifikovanih nanočestica na njihova dinamickomehanička svojstva (modul sačuvane i izgubljene energije i tangens gubitaka) u različitom temperaturnom intervalu pri različitim frekvencijama); 3) eksperimentalna istraživanje uticaja procesnih uslova brizganja i toplog presovanja hibridnih laminatnih nonokompozita sa matricom od poli (vinil butirala) sa razlicitim udelom modifikovanih cestica silicijum dioksida na makromehanicka svojstva (Jungov modul elasticnosti, zatezna cvrstoca, prekidno izduženje); 4) eksperimentalna ispitivanja otpornosti na razaranje dobijenih hibridnih nanokompozitnih materijala na udar velikim energijama i brzinama (standardna balisticka ispitivanja sa municijom u realnim uslovima).The purpose of this dissertation is to investigate the effects of lamination and hybrid soft armor systems through ballistic impact. The investigation was carried out by using dynamic mechanical analysis and actual ballistic testing. The most important conclusions derived from this research are that lamination of the systems with very low resin content are superior to multiple non-laminated systems, and this advance could be improved further by hybrid systems using nanomodified fabric layers on the impact side and relatively tighter woven fabrics between the layers. This dissertation reports the preparation of SiOR2R and TiOR2R/poly (vinyl butyral) nanocomposites with enhanced dynamic mechanical properties. Silica and titania nanoparticles were introduced in the matrix as the neat powder and as colloidal sol using the melt mixing process. Composites reinforced with colloidal sol silica and titania showed higher mechanical properties than the ones reinforced with as-received particles. When sol TiOR2R particles are used, the highest increase of storage modulus of about 54% is obtained for 5 wt% loading, while for sol SiOR2R, the storage modulus increases with the addition of nanosilica with the largest increase of about 99% for 7 wt% loading. In addition, nanocomposites were introduced within Kevlar/PVB composites. The addition of 5 wt% silica and titania colloidal sol lead to the remarkable increase of the storage modulus for about 98 and 65%, respectively. Largest contribution of nanoreinforcements in lowering the glass transition temperature is observed for 7 wt% loading of TiOR2R and SiOR2R colloidal sol. This study reports the manufacture of new fabric forms from the preparation of hybrid laminated multi-axial composites with enhanced thermo-mechanical properties. Thermal and dynamic mechanical analysis of polymer matrix films and fabricated hybrid composites were employed in order to determine the optimal material composition and reinforcement content for composites with improved viscoelastic properties. The introduction of 5 wt. % silica nanoparticles in a composite of p-aramid– poly(vinyl butyral) led to significant improvements in the mechanical properties, and the addition of silane coupling agents yielded maximal values of the storage modulus for hybrid nanocomposites. The introduction of silane led to a better dispersion and deagglomeration of SiOR2R particles and to the formation of chemical bonds between organic and inorganic constituents, or p-aramid–poly(vinyl butyral) composites. In this way, the mobility of macromolecules was reduced, which can be seen from the decreasing value of damping factor for the p-aramid–poly(vinyl butyral) composite. Analysis of the glass transition temperature of the composite with amino-functionalized silica nanoparticles revealed improved thermal stability in addition to the aforementioned mechanical properties of the tested materials

Mission oriented R and D and the advancement of technology: The impact of NASA contributions, volume 2

NASA contributions to the advancement of major developments in twelve selected fields of technology are presented. The twelve fields of technology discussed are: (1) cryogenics, (2) electrochemical energy conversion and storage, (3) high-temperature ceramics, (4) high-temperature metals (5) integrated circuits, (6) internal gas dynamics (7) materials machining and forming, (8) materials joining, (9) microwave systems, (10) nondestructive testing, (11) simulation, and (12) telemetry. These field were selected on the basis of both NASA and nonaerospace interest and activity