Search NASA⌕ Search

SEARCH · Search NASA

Results for “COMPRESSION BUCKLING”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Nonlinear panel flutter in a rarefied atmosphere - Aerodynamic shear stress effects

The panel flutter phenomenon is studied assuming free-molecule flow. This kind of analysis is relevant in the case of hypersonic flight vehicles traveling at high altitudes, especially in the leeward portion of the vehicle. In these conditions the aerodynamic shear can be expected to be considerably larger than the pressure at a given point, so that the effects of such a loading are incorporated into the structural model. This is accomplished by introducing distributed longitudinal and bending moment loads. The former can lead to buckling of the panel, with the second mode in the case of a simply-supported panel playing a important role, and becoming the dominant mode in the solution. The presence of equivalent springs in the longitudinal direction at the panel's ends also becomes of relative importance, even for the evaluation of the linear flutter parameter. Finally, the behavior of the system is studied in the presence of applied compressive forces, that is, classical buckling.

Resende, Hugo B.↗
NASA NTRS2012

TPSAS-NF1676L-13538-DND

Highly loaded composite struts from a proposed truss-based Altair lunar lander descent stage concept were selected for development under NASA's Advanced Composites Technology program. Predicted compressive member forces during launch and ascent of over -100,000 lbs were much greater than the tensile loads. The development of a capability for experimental evaluation of the structural performance of these struts is presented. Strut lengths range from 60 to over 120 inches, and compressive launch and ascent loads can exceed -100,000 lbs, or approximately two times the corresponding tensile loads. Allowing all possible compressive structural responses, including elastic buckling, were primary considerations for designing the test hardware. NASA's industry partner designed and built highly loaded struts that were delivered to NASA for testing. Their design, fabricated on a washout mandrel, had a uniform-diameter composite tube with composite tapered ends. Each tapered end contained a titanium end fitting with facing conical ramps that are overlaid and overwrapped with composite materials. The highly loaded struts were loaded in both tension and compression, with ultimate failure produced in compression. Test results for these struts are presented and discussed, along with measured deflections, strains and observed failure mechanisms.

K Chauncey Wu↗
NASA NTRS1999

Anisotropic Plasticity of BN Nanotubes

Plastic collapse of compressed BN nanotubes are investigated and compared with carbon nanotubes of similar nature. Using a generalized tight-binding molecular dynamics (GTBMD) method for system containing B, N and C atoms we compute stiffness and plastic collapse of BN and C nanotubes under axial compression. For small compressional strain, BN nanotubes are found to be about 92% as stiff as similar C nanotubes. Due to BN bond buckling effect, however, the elastic limit of BN nanotubes is found to be more than C nanotubes. A route to plasticity is explored in which we find that at elastic limit the accumulated strain is released by a local plastic deformation of the nanotube. The mechanism of strain release and the resulting plastic deformation, however. are anisotropic in nature. The strain is released preferentially towards N as leading edge of a buckled BN bond and the tube, compressed at both ends, plastically collapses preferentially towards one end. Details of the anisotropic plasticity and prospective applications will be discussed in this presentation.

Madhu, Menon↗
NASA NTRSDate not supplied

Buckling and Failure Tests of a Subscale Composite Cylinder

A subscale solid laminate composite cylinder 31.5-in. diameter and 47.8 in. long with a [23/0/-23]4S layup known as NDL-1 was designed to fail in buckling and tested in axial compression to collapse twice. The proposed paper will focus on comparing the behavior of NDL-1 from the first test to failure (TTF-1) and the second test to failure (TTF-2). NDL-1 had a peak load of 466.3 kips during TTF-1 and a peak load of 390.4 kips, 15.5% lower, but with a similar stiffness, during TTF-2. Failure initiated at the 200º circumferential location in TTF-1, and at the 30º circumferential location in TTF-2. Though failure initiated at different locations, a similar radial deformation pattern was present just prior to collapse in TTF-1 and TTF-2. A shallow delamination occurred due to the initial failure event in TTF-1, and the damage had no influence on the response of NDL-1 during TTF-2. In the end, it was determined that NDL-1 failed in buckling during TTF-1 and TTF-2, and the second test to failure of NDL-1 highlighted interesting observations with respect to the effect of damage.

Buckling↗
NASA NTRS1982

Analytical and experimental vibration and buckling characteristics of a pretensioned stayed column

Modal vibration tests to determine lateral modes of vibration of a stayed column and static axial compression tests to determine the column's buckling and postbuckling behavior have been performed. Effects of stay tension levels and vibration-load interaction are presented. Two finite element models are used to analyze the column, a three-dimensional frame using NASTRAN and an equivalent two-dimensional frame using an exact dynamic stiffness matrix. Both analyses correlated well with the linear vibration and buckling experimental data. Results indicate premature buckling of the column due to vibration-load interaction and nonlinear oscillations due to stay slackening. Postbuckling behavior of the column is unusual because of stay slackening and results in a postbuckling restoring force of less than the bifurcation buckling load. Guidelines for design of pretensioned structures are presented which consider buckling, postbuckling and vibration behavior.

Belvin, W. K.↗
NASA NTRS1990

Postbuckling of long thick plates in compression including higher order transverse shearing effects

Aluminum plates of various length/width ratios loaded in compression are examined analytically in terms of buckling and postbuckling for comparison with classical theory. The plates are considered to be subjected to longitudinal compressive displacement with no edge stress and are assumed to be simply supported at the side edges. The average longitudinal direct stresses are computed to plot characteristic curves by means of the following theories: 3D flexibility, higher-order shear deformation, first-order shear deformation, and classical von Karman. The 3D flexibility approach yields the lowest results with more unknowns than the higher-order shear-deformation method. The 3D flexibility approach is considered to be the most accurate, and it is shown that the calculated resultants and displacements tend to vary when consideration is given to the effects of transverse shear.

Stein, Manuel↗
DOE OSTI2025

Magnetized, radiofrequency-driven hollow cathode chemical-vapor deposition of ultrathick hydrogenated amorphous carbon

Amorphous carbon is an attractive material for next-generation inertial confinement fusion (ICF) ablators due to its amorphous structure, tunable density, compatibility with dopants, chemical inertness, and mechanical robustness. Ablators are typically deposited as ultrathick (10–200 μm) coatings on removable spherical templates. The deposition of such thick amorphous carbon films is challenging due to high intrinsic compressive stress, which causes film buckling and delamination. Here, we study the deposition of amorphous carbon films by magnetized, radiofrequency-driven hollow cathode chemical vapor deposition with a custom-designed source in Ne plasmas. Emphasis is on the hollow-cathode source design and effects of the plasma discharge power and the precursor flow rate on film properties. We demonstrate deposition rates of >1 μm/h for films with hydrogen content of ∼40 at. %, densities of 1.1–1.7 g/cm 3 , and trace quantities of oxygen impurities. In conclusion, we also demonstrate the feasibility of depositing thick hydrogenated amorphous carbon films (∼30 μm) for ICF applications.

Carbon based materials↗
NASA NTRS1978

Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data.

Royster, D. M.↗
NASA NTRS1988

Instability-related delamination growth of embedded and edge delaminations

Compressive loads can cause local buckling in composite laminates that have a near surface delamination. This buckling causes load redistribution and secondary loads, which in turn cause interlaminar stresses and delamination growth. The goal of this research was to enhance the understanding of this instability-related delamination growth in laminates containing either an embedded or an edge delamination.

Whitcomb, John D.↗
NASA NTRS1998

Compression Strength of Composite Primary Structural Components

Research conducted under NASA Grant NAG-1-537 focussed on the response and failure of advanced composite material structures for application to aircraft. Both experimental and analytical methods were utilized to study the fundamental mechanics of the response and failure of selected structural components subjected to quasi-static loads. Most of the structural components studied were thin-walled elements subject to compression, such that they exhibited buckling and postbuckling responses prior to catastrophic failure. Consequently, the analyses were geometrically nonlinear. Structural components studied were dropped-ply laminated plates, stiffener crippling, pressure pillowing of orthogonally stiffened cylindrical shells, axisymmetric response of pressure domes, and the static crush of semi-circular frames. Failure of these components motivated analytical studies on an interlaminar stress postprocessor for plate and shell finite element computer codes, and global/local modeling strategies in finite element modeling. These activities are summarized in the following section. References to literature published under the grant are listed on pages 5 to 10 by a letter followed by a number under the categories of journal publications, conference publications, presentations, and reports. These references are indicated in the text by their letter and number as a superscript.

Johnson, Eric R.↗
NASA NTRS2004

Deformations of Flat Unsymmetric Laminates Subjected to Inplane Loads

The geometrically nonlinear deformation response of initially flat unsymmetric cross-ply laminates subjected to an inplane compressive load and two sets of boundary conditions is studied. Stability of the deformations is considered. At issue is whether or not the plate remains flat with increased compressive loading, and whether it buckles. A semi-infinite unsymmetric cross-ply laminate is used to show the combined effects of geometric nonlinearities and bending-stretch coupling. Finite element results for finite laminates are then presented, and it is shown that to a large degree the boundary conditions control the character of the deformation response. It appears that clamped boundary conditions support buckling behavior, in the classic sense of bifurcation, whereas simply-supported conditions do not.

Hyer, Michael W.↗
NASA NTRS2005

Blended-Wing-Body (BWB) Fuselage Structural Design for Weight Reduction

Structural analysis and design of efficient pressurized fuselage configurations for the advanced Blended-Wing-Body (BWB) flight vehicle is a challenging problem. Unlike a conventional cylindrical pressurized fuselage, stress level in a box type BWB fuselage is an order of magnitude higher, because internal pressure primarily results in bending stress instead of skin-membrane stress. In addition, resulting deformation of aerodynamic surface could significantly affect performance advantages provided by lifting body. The pressurized composite conformal multi-lobe tanks of X-33 type space vehicle also suffered from similar problem. In the earlier BWB design studies, Vaulted Ribbed Shell (VLRS), Flat Ribbed Shell (FRS); Vaulted shell Honeycomb Core (VLHC) and Flat sandwich shell Honeycomb Core (FLHC) concepts were studied. The flat and vaulted ribbed shell concepts were found most efficient. In a recent study, a set of composite sandwich panel and cross-ribbed panel were analyzed. Optimal values of rib and skin thickness, rib spacing, and panel depth were obtained for minimal weight under stress and buckling constraints. In addition, a set of efficient multi-bubble fuselage (MBF) configuration concept was developed. The special geometric configuration of this concept allows for balancing internal cabin pressure load efficiently, through membrane stress in inner-stiffened shell and inter-cabin walls, while the outer-ribbed shell prevents buckling due to external resultant compressive loads. The initial results from these approximate finite element analyses indicate progressively lower maximum stresses and deflections compared to the earlier study. However, a relative comparison of the FEM weight per unit floor area of the segment unit indicates that the unit weights are still relatively higher that the conventional B777 type cylindrical or A380 type elliptic fuselage design. Due to the manufacturing concern associated with multi-bubble fuselage, a Y braced box-type fuselage alternative with special resin-film injected (RFI) stitched carbon composite with foam-core was designed by Boeing under a NASA research contract for the 480 passenger version. It is shown that this configuration can be improved to a modified multi-bubble fuselage which has better stress distribution, for same material and dimension.

Mukhopadhyay, V.↗
NASA NTRS2011

Highly Loaded Composite Strut Test Development

Highly loaded composite struts, representative of structural elements of a proposed truss-based lunar lander descent stage concept, were selected for design, development, fabrication and testing under NASA s Advanced Composites Technology program. The focus of this paper is the development of a capability for experimental evaluation of the structural performance of these struts. Strut lengths range from 60 to over 120 inches, and compressive launch and ascent loads can exceed -100,000 lbs, or approximately two times the corresponding tensile loads. Allowing all possible compressive structural responses, including elastic buckling, were primary considerations for designing the test hardware.

Wu, K. Chauncey↗
NASA NTRS2006

A Numerical and Experimental Study of Compression-Loaded Composite Panels With Cutouts

Results from a numerical and experimental study on the effects of laminate orthotropy and circular cutout size on the response of compression-loaded composite curved panels are presented. Several 60-in-radius composite panels with four different laminate configurations were tested with cutout diameters that range from 10% to 60% of the panel width. Finite-element analyses were performed for each panel in order to identify the effects boundary conditions, measured initial geometric imperfections and thickness variations had on the nonlinear and buckling behavior of the panels. The compression-loaded panels considered herein exhibited two separate types of behavior depending on the laminate stacking sequence and cutout size. More specifically, some of the panels exhibited the classical snap-through type buckling response; however, some of the panels exhibited a monotonically increasing stable response and achieved compressive loads in excess of twice the predicted linear bifurcation buckling load. In general, the finite-element analyses were able to predict accurately the nonlinear response and buckling loads of the panels and the prebuckling and postbuckling out-of-plane deformations and strains.

Thornburgh, Robert P.↗
NASA NTRS1978

Experimental and finite element investigation of the buckling characteristics of a beaded skin panel for a hypersonic aircraft

As part of NASA's continuing research into hypersonics and 85 square foot hypersonic wing test section of a proposed hypersonic research airplane was laboratory tested. The project reported on in this paper has carried the hypersonic wing test structure project one step further by testing a single beaded panel to failure. The primary interest was focused upon the buckling characteristics of the panel under pure compression with boundary conditions similar to those found in a wing mounted condition. Three primary phases of analysis are included in the report. These phases include: experimental testing of the beaded panel to failure; finite element structural analysis of the beaded panel with the computer program NASTRAN; a summary of the semiclassical buckling equations for the beaded panel under purely compressive loads. Comparisons between each of the analysis methods are also included.

Siegel, W. H.↗
NASA NTRS1986

Buckling characteristics of hypersonic aircraft wing tubular panels

The buckling characteristics of Rene 41 tubular panels installed as wing panels on a hypersonic wing test structure (HWTS) were determined nondestructively through use of a force/stiffness technique. The nondestructive buckling tests were carried out under different combined load conditions and different temperature environments. Two panels were subsequently tested to buckling failure in a universal tension compression testing machine. In spite of some data scattering because of large extrapolations of data points resulting from termination of the test at a somewhat low applied load, the overall test data correlated fairly well with theoretically predicted buckling interaction curves. The structural efficiency of the tubular panels was slightly higher than that of the beaded panels which they replaced.

Ko, William L.↗