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Davis, R. C.

Publications and source records attributed to Davis, R. C..

30 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Buckling test of a 3-meter-diameter corrugated graphite-epoxy ring-stiffened cylinder

A three m diameter by three m long corrugated cylindrical shell with external stiffening rings was tested to failure by buckling. The corrugation geometry for the graphite epoxy composite cylinder wall was optimized to withstand a compressive load producing an ultimate load intensity of 157.6 kN/m without buckling. The test method used to produce the design load intensity was to mount the specimen as a cantilevered cylinder and apply a pure bending moment to the end. A load introduction problem with the specimen was solved by using the BOSOR 4 shell of revolution computer code to analyze the shell and attached loading fixtures. The cylinder test loading achieved was 101 percent of design ultimate, and the resulting mass per unit of shell wall area was 1.96 kg/sq m.

Davis, R. C.↗
NASA NTRS1982

Design detail verification tests for a lightly loaded open-corrugation graphite-epoxy cylinder

Flat corrugated graphite-epoxy panels were tested in compression to verify selected design details of a ring-stiffened cylinder that was designed to support an axial compressive load of 157.6 kN/m without buckling. Three different sizes of subcomponent panels, with the same basic corrugation geometry, were tested: (1) 60.96-cm-long by 45.72-cm-wide panels to evaluate the local buckling strength of the shell wall design; (2) 91.44-cm-long by 45.72-cm-wide panels to evaluate a longitudinal joint and the load-introduction method; and (3) 254.0-cm-long by 91.44-cm-wide panels with four simulated-ring stiffeners to evaluate the ring-attachment method. The test results indicate that the modified shell-wall design, the longitudinal joint, the load-introduction method, and the stiffener-attachment method for the proposed cylinder have adequate strength to support the design load.

Davis, R. C.↗
NASA NTRS1980

Stress analysis and buckling of J-stiffened graphite-epoxy panel

A graphite epoxy shear panel with bonded on J stiffeners was investigated. The panel, loaded to buckling in a picture frame shear test is described. Two finite element models, each of which included the doubler material bonded to the panel skin under the stiffeners and at the panel edges, were used to make a stress analysis of the panel. The shear load distributions in the panel from two commonly used boundary conditions, applied shear load and applied displacement, were compared with the results from one of the finite element models that included the picture frame test fixture.

Davis, R. C.↗
NASA NTRS1978

Design and fabrication of a large graphite-epoxy cylindrical shell

This paper describes the design and fabrication of a 10-foot diameter by 10-foot long graphite-epoxy cylinder and reports the results of developmental tests conducted with sample joints, material coupons, and stiffening ring elements. The cylindrical shell is a ring-stiffened, open corrugation design using T300/5208 graphite-epoxy tape as the basic material for the shell wall and stiffening rings. The cylinder is designed to withstand bending loads producing the relatively low maximum load intensity of 900 lb/in. The resulting shell wall weight, including stiffening rings and fasteners, is 0.37 lb/sq ft. The shell weight expected in the graphite-epoxy cylinder represents a weight savings of approximately 23 percent over that of a comparable aluminum shell. The cylinder wall was built in three flat segments which were wrapped to the cylindrical shape upon assembly. Such an approach, made possible by the flexibility of the thin corrugated wall in a radial direction, proved to be a simple one.

Johnson, R., Jr.↗
NASA NTRS1977

Effect of end-ring stiffness on buckling of pressure-loaded stiffened conical shells

Buckling studies were conducted on truncated 120 deg conical shells having large end rings and many interior reinforcing rings that are typical of aeroshells used as spacecraft decelerators. Changes in base-end-ring stiffness were accomplished by simply machining away a portion of the base ring between successive buckling tests. Initial imperfection measurements from the test cones were included in the analytical model.

Davis, R. C.↗
NASA NTRS1975

Buckling tests of three 4.6 meter diameter aluminum honeycomb sandwich conical shells loaded under external pressure

Three aluminum honeycomb sandwich conical shells with a 120 apex angle and a 4.6-m (15.0-ft) base diameter were loaded to failure by a uniform external pressure. The cones differed from one another only in the thickness of their respective face sheets. Test specimen details, test procedure, and test results are discussed. Both buckling and prebuckling data are compared with appropriate theoretical predictions, and good agreement was obtained between test and theory. Extensive imperfection measurements were made and reported on the three cones in the as fabricated condition.

Anderson, J. K.↗
NASA NTRS1974

Minimum-weight designs for hat-stiffened composite panels under uniaxial compression

Optimum hat-stiffened compression panel designs are determined by a structural synthesis technique. The effects of simplifying assumptions made in the buckling analysis for the optimization program are investigated by a linked plate element program. Optimization results for hat-stiffened graphite-epoxy panels show a 50-percent weight savings over optimized aluminum panels. Composite panels are shown to possess a variety of proportions at nearly constant weight.

Agarwal, B.↗
NASA NTRS1974

Interactive design of large end rings on stiffened conical shells using composites

Design study methods and results for a composite reinforced base ring for the conical aeroshell structure of the planetary lander vehicle for Project Viking, an unmanned mission to Mars, are presented. The aeroshell is a ring and stringer-stiffened conical shell structure having a half angle of 70 degrees with a large base ring mounted at the outer edge of the cone and a large pay-load ring in the interior with many smaller rings spaced along the inside shell surface. The purpose of the structure is to develop the aerodynamic drag required to decelerate the lander in the Mars atmosphere to facilitiate a soft landing. The design of a shell structure of this complexity requires the use of the latest technology available in a large general-purpose shell buckling program. The large general-purpose non-linear shell buckling program (BOSOR 2) which was used for this purpose is described.

Davis, R. C.↗
NASA NTRS1973

Experiments on stiffened conical shell structures using cast epoxy models

Description of a casting technique for fabricating high-quality plastic structural models, and review of results regarding the use of such specimens to parametrically study the effect of base ring stiffness on the critical buckling pressure of a ring-stiffened conical shell. The fabrication technique involves machining a metal mold to the desired configuration and vacuum-drawing the plastic material into the mold. A room-temperature curing translucent thermoset epoxy was the casting material selected. A shell of revolution computer program which employs a nonlinear axisymmetric prebuckling strain field to obtain a bifurcation buckling solution was used to guide the selection of congifurations tested. The shell experimentally exhibited asymmetric collapse behavior, and the ultimate load was considerably higher than the analytical bifurcation prediction. The asymmetric buckling mode shape, however, initially appeared at a pressure near the analysis bifurcation solution.

Williams, J. G.↗
NASA NTRS1968

Analysis of flutter in tape transport systems

Effect of flutter on digital data is recorded by magnetic tape recorders used with instrumentation systems. Major effect for both FM and direct recording techniques is shown to be a perturbation of the signal time base.

Davis, R. C.↗