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This report covers the design, analysis, manufacturing and testing done during the last portion of Phase II, detail design, and the first portion of Phase III, Fabrication, of the Advanced Metallic Air Vehicle Structure (AMAVS) program. All drawings for the wing carry through structure, simulated fuselage and test fixture were completed and significant progress was made in manufacturing each of these items. A weight reduction effort was necessary in order to meet the weight reduction goal for the wing carry through structure after incorporation of the updated loads data. This effort has been completed and was successful. Delivery of material for manufacture of the wing carry through structure is complete except for the 10 Ni steel for the upper lugs. Manufacturing processes successfully completed include flame cutting of thick plates of 10 Ni steel and beta annealed 6Al-4V titanium, Electron Beam (EB) welding of both of these materials, Gas Tungsten Arc (GTA) welding of 10 Ni steel, machining of 10 Ni steel and 6Al-4V titanium and bonding of titanium sandwich panels. Most tooling for detail parts is complete and the assembly fixtures are complete.

The report summarizes the first phase of an effort to develop equipment and procedures to inspect sandwich panels in air transportable shelters in the field. A rapid and simple-to-operate system has been developed, utilizing a unique eddy sonic technique for metal-faced panels and pitch-catch ultrasonic techniques for nonmetal faced panels. The location(s) of debonds and free moisture in the panel are reliably detectable with the system. A functional model has been successfully field tested. (Author)

The patent describes a process for fabricating a structure by vacuum brazing tantalum alloy elements in which a columbium-vanadium brazing foil is placed between surfaces of the elements to be joined. A coating of yttria powder is applied to surfaces of elements that will be in contact with a tungsten hearth plate and tungsten pellets; the structure is positioned on the tungsten hearth plate in a vacuum heating zone with tungsten pellets disposed on top of the portion of the upper element to be joined so as to exert pressure thereon and control the gap between the surfaces to be joined; the elements are heated in the vacuum heating zone to a temperature sufficient to melt the brazing foil. The vacuuum brazing process is particularly suitable for use in fabricating honeycomb sandwich panels, using tantalum alloy structural elements., Supersedes AD-164 555.

The report presents the development of rational methods of structural optimization for flat, corrugated core (single truss core) and web-core sandwich panels under two loading conditions: in-plane shear loads, and combined uniaxial compression and in-plane shear loads. These methods provide a means by which minimum weight structures can be designed for a given load index, plate width, length, and face and core materials. The methods developed can be used as a means of rational material selection by comparing weights of optimum construction for various material systems as a function of applied load index. The methods are sufficiently general to account for orthotropic or isotropic face and core materials and various boundary conditions. Design procedures are given in detail for the design engineer to use.

Rational methods are developed of structural optimization for flat, corrugated core and web core sandwich panels subjected to uniaxial compressive loads. These methods provide a means by which such panels can be designed with minimum weight for a given load index, panel width, panel length, and face and core materials. Methods presented permit a rational material selection by comparing the weights of the optimum construction for several material systems as a function of load index. The methods account for both isotropic or orthotropic face and core materials and various boundary conditions.

A nondimensional design technique is developed to obtain the minimum weight of structural components (columns, plates, and beams) subjected to an aerospace environment. Design curves are developed and presented for various structural configurations in terms of the applied loads and geometric material parameters which can be readily evaluated. The design technique can be employed to obtain, in a relatively simple and rapid manner, preliminary estimates of the structural design weight as well as a good approximation to the final design. The design procedure for minimum weight is illustrated for a truss-like spar and a wing section which are typical of aerospace structures.

The problem of relating intermodal cargo container cost, weight, and useable volume to container size, configuration, loading, and construction type is handled by comparing simplified preliminary container designs. To facilitate comparision, a common container base and panel supporting framework is assumed, with panel weights added to obtain total container weight. The panels for these designs are obtained through computer programs which optimize the panels with respect to weight through a stress-limited beam approach. These relationships are graphically presented for a variety of parameters. It is concluded that true intermodal containers meeting both the high-g requirements implied by air liftability and the versatile handling requirements of commercial containers can be expected to be somewhat heavier and more expensive than current commercial containers. The more expensive constructions can reduce this weight difference while retaining high interior volume, but cannot influence the strong effect of the handling penalties without an extensive test program to determine the feasibility of the lightened construction. If extremely light containers are needed to suit the air mode, consideration should be given to limiting handling capabilities to top-lift only. (Author), Prepared in cooperation with Wm. Ryder and Associates, St. CLAIR Shores, Mich.

The refinement of the Cu and Ag based exothermic adhesive systems for overlap bonding, fabricating overlap specimens specified in the contract was completed. The development of an exothermic adhesive composition and associated procedures for honeycomb panel bonding continued. Stainless steel lap shear strengths using Ag base exotherms were consistently abo ve 5300 psi with most failures in the stainless parent metal, the average strength being 9173 psi. No appreciable change in strength was noted up to 600 F. At 800 F this average was 8941 psi. Bend tests demonstrated the bonds were metallic, with little or no included glass. Honeycomb core cell bonding to skins was achieved but core cell burn through, although greatly reduced, still remained a problem. (Author)

A method of design is presented for sandwich constructions having honeycomb-type cores with thick walls. Equations are derived for calculating the critical stress in the facings of such sandwich panels. Tabulated results of edgewise compression tests are included. Measurements of strain indicated that the honeycomb core material is substantially an orthotropic material., In cooperation with Air Force-Navy-Civil Committee on Aircraft Design Criteria.

Thermal insulation for protecting airframe structures from aerodynamic and combustor heating is discussed. The objective is to obtain an insulation which can withstand thermal strains on the hot surface and also permit the use of brittle materials in such a way that the cold internal structure can deflect under load. Several test panels of stainless steel and one of aluminum oxide shingles were fabricated and their thermal conductivity determined. The results indicate that the system is competitive with others employing fibrous insulators which are limited to 2000 F service. Theoretical analysis of the heat transfer processes was made and this shows that at temperatures around 3000 to 5000 F, the shingle configuration would be considerably more efficient than solid materials such as zirconia and alumina. (Author)

Non-destructive tests were conducted on Phase II full-scale aircraft bonded structures. The Fokker Bond Tester and Coinda-Scope indicated all control panels were acceptable. The STUB-meter indicated sufficient defects in the FM-47 control panel to classify this panel as unacceptable. All three of these instruments detected sub-standard conditions in the panels containing bonding variables except for the FM-58 panels. This group was indicated good by all instruments. The Sonoray 5 indicated that the FM-47 and HT-424 panels containing bond variables were completely defective, but test results on the other panels were very erratic. Further analysis must await destructive test data to determine if any correlation exists between test readings and actual bond strength. Only the Fokker Bond Tester was capable of detecting a ddifference in the Phase I panels that had been subjected to elevated temperatures and fatigue. Also, this instrument appears to be more sensitive to degrees of porosity in the glue line than the other instruments. (Author)

Diaphragms of thin titanium and aluminum alloy stainless steel sheet have been pressurized with liquid and gaseous oxygen and gaseous nitrogen, and subjected to impact from a high velocity, small steel projectile. Titanium alloys burn in the oxygen environment, but do not burn in either the sea-level air environment or pure nitrogen at pressures up to 60 psi. Films of WD-40 may inhibit the oxidation of titanium in gaseous oxygen, but have little or no effect in retarding combustion of the titanium in liquid oxygen. Although stainless steel and aluminum are relatively unreactive in the oxygen environment, these metals will burn when placed in contact with burning titanium. Moreover, all metal diaphragms under 60-psi pressure may catastrophically rip when a certain crack length or perforated area is attained. Care should be exercised in the design of an aerospace vehicle to keep thin gauge titanium sheet away from contact with liquid or gaseous oxygen.

Sandwich specimens were evaluated that had aluminum facings of various thicknesses and a solid core of Sitka spruce in which a cell of a honeycomb core material was simulated by a round hole. A few tests involving honeycomb cores were made, and results of these were found to agree with those of the other tests for the stress at the start of dimpling of the facings. The maximum stress in the facings of the honeycomb core specimens was lower at failure than for the specimens with wood cores. At failure, the honeycomb core sandwich specimens had a wrinkle-type failure in the facing, with some failure in the bond between the facing and core. An empirical formula was obtained that can be used to estimate the critical stress at which dimpling of the facing over the cell voids beings., In cooperation with Wisconsin U., Madison, Contract AF 33(657)63-358. Revision of Rept. no. 1817, AD53946.

The Reconnaissance Exploitation Test Shelter (RETS) was designed as a very flexible work facility for photo interpretation. Work stations may be positioned in any arrangement desired, within the constraints of the 8 ft x 8 ft x 23 ft long shelter. Three-phase, 60 cycle, 110/220 volts power is supplied by two 12KW diesel generators; and air conditioning is provided by two 40,000 Btu units connected to the shelter by flexible ducts. The internal equipment compliment consists of photo interpretation light tables, stereoscones, and other photo interpretation tools, cabinets, and aluminum pegboard on both side walls for shelving, hooks, etc. Spare parts for one year's operation are included for the critical equipment.

This report covers the design and structural requirements of a thinwall lightweight field and mobile shelter capable of transport by truck, cargo, 3/4 ton, 4 x 4, M-37, and by fixed or rotary wing aircraft.

The test program purpose is to characterize a singular graphite/epoxy system with the data divided into two categories: baseline data and environmental effects data. The purpose of the baseline data is to provide the basic materials, bonded and mechanical joint data, and fundamental configuration data at room, elevated, and subzero temperatures to support the design of graphite/epoxy airframe structural components. These data are augmented by the environmental effects data, which will establish the influence of the operating environment of high-performance aircraft on the design allowables of the graphite/epoxy system studies., See also Volume 3, AD878221.

This report presents a theoretical analysis is presented for the behavior of long, circular, cylindrical shells of sandwich construction under axial compressive loads. The analysis is designed to evaluate the effects of the relatively low shearing moduli of sandwich cores on buckling stresses. Families of curves are presented for use in designing shells of sandwich construction having isotopic facings and orthotropic or isotropic cores. The results of the theoretical analysis were compared with those obtained from tests on a series of curved panels. It was found that the theory applied reasonable well to curved plates of sizes sufficient to include at least one ideal buckles. Application of the theory thus is not limited to long, complete cylinders.

A theoretical analysis is presented of the behavior of sandwich panels having dissimilar facings of unequal thickness when loaded in edgewise shear. Design curves are presented for simply supported panels with dissimilar facings. Approximate formulas are included for clamped panels. The analysis is compared with results of tests on 28 square panels of symmetrical isotropic sandwich constructions. Included are descriptions of testing techniques employed to induce pure shear in the test panels. A method is given for predicting the behavior at stresses exceeding proportional-limit values.

The use of superalloy and refractory alloy honeycomb composites for heat shield and structural components in re-entry vehicle applications is outlined followed by a detailed comparison between experimentally measured and analytically predicted thermal conductance values on superalloy honeycomb composites. The experimental thermal conductance determinations on L-605 cobalt alloy panels of variable geometry were made in high vacuum and air environments using a high temperature absolute thermal conductivity apparatus. Measurements were made over the range from 500 to 2000 F maintaining the temperature drop across the specimens below 200 F. Average precision of the results was plus or minus 7% while the accuracy was established to be plus or minus 10% based on initial calibration. The thermal conductances in air environment were between 60 and 100% above comparable values for the panels tested under vacuum conditions. Analysis of the results indicated that gaseous conduction and convection accounted for only a small fraction of the difference, the main effect being a large increase in the radiative contribution produced by increased emittance of the alloy through surface oxidation.

The Bresse equation for the buckling of rings under radial pressure is modified to predict the general-instability collapse pressure of cellular sandwich shells under hydrostatic pressure. The validity of the equation is demonstrated by implosion experiments with carefully designed cellular sandwich shells, the general-instability collapse pressures of which are compared with the results obtained by the modified Bresse equation. The results indicate that the modified equation predicts the general-instability collapse pressure of cellular sandwich shells within 5 per cent. This equation is recommended for use only when the ratio of shell ring depth to shell mean diameter is less than 0.1.

Curves and formulas for use in computing the buckling of flat panels of sandwich construction under edgewise compressive loads are presented. Included are curves for constructions with isotropic facings and either isotropic or orthotropic cores., Also under contract NAER-01684. Issued in cooperation with the ANC-23 Panel on Sandwich Construction of the Departments of the Air Force, Navy, and Commerce.

On the basis of static shear and flexure fatigue tests, it is recommended that 97Ag-3Li braze all foil be used when repair TIG spot welding of 17-7PH stainless steel. This alloy can produce a spot welded-brazed joint which has 11% more static lap shear strength and 114% more flexure fatigue strength. TIG braze joints should not be used as they have less strength than normal TIG spot welded 17-7PH. The filler wire added to the weld nugget should be 17-7PH in preference to Type 308.

Standard and nonstandard types of radome wall structures are discussed to aid in determining practical design concepts for radar systems operating at Ka-band frequencies. Transmission efficiencies of selected radome panels are illustrated and compared for a hypothetical radome design problem.

Honeycomb sandwich panels using Mo and Nb core and facings can be brazed to provide lightweight structural coverings for high temperature application on an aerospace vehicle. The panel configurations selected for fabrication simulate a hot structural and a radiant heat shield application . M (Mo-0.5Ti-0.08Zr) Mo and D-36 (Nb-10Ti-5Zr) Nb alloys were chosen for use on the program. Special tools and procedures were developed to fabricate the honeycomb core. All Mo welding will be accomplished by electron beam welding. A 4200 F cold-wall vacuum furnace will be used to braze the honeycomb test panels. A quartz-lamp facility will be used to heat the panels for structural testing. Thermal-cyclic and sonic fatigue tests will be performed on heat shield test panels. A 4000 F cold-wall vacuum test chamber will be used to determine material and honeycomb proporties.

A method is presented for optimizing, on a weight basis, flat truss-core sandwich panels under lateral loads. To solve this type of problem by equating the stress level for all failure modes requires a knowledge of the stress distribution throughout the panel for the given loading. There are no available stress analysis methods of sufficient sophistication for corrugated panels under lateral loading; hence, a large portion of this report is devoted to the development of such a method of analysis. The method is essentially a deformation method; however, a technique of using Fourier type transformations makes the solution more tractable.

An integrated procedure is presented for applying the variational equation of motion to the approximate analysis of nonlinear vibrations of homogeneous and layered plates and shells involving large deflections. The procedure consists of a sequence of variational approximations. The first of these involves an approximation in the thickness direction and yields a system of equations of motion and boundary conditions for the plate or shell. Subsequent variational approximations with respect to the remaining space coordinates and time, wherever needed, lead to a solution to the nonlinear vibration problem. The procedure is illustrated by a study of the nonlinear free vibrations of homogeneous and sandwich cylindrical shells, and it appears to be applicable to still many other homogeneous and composite elastic systems.

Development of STRESSKIN, an all resistance welded stainless steel honeycomb sandwich panel., Progress and achievements made in manufacturing research and development of STRESSKIN, an all resistance welded stainless steel honeycomb sandwich panel.

A new variational principle is presented, which may be considered as a generalized Hamilton's principle. The principle is made use of in the derivation of the complete system of equations for a sandwich cylindrical shell, which are reducible to those of a sandwich plate as a special case. The way the equations are derived is also new. The equations of the sandwich plate and cylindrical shell are used to investigate the undamped vibrations of these structures. Of particular interest are an analysis of the coupling between the flexural and extensional motions of the sandwich cylindrical shell and a demonstration of the importance of transverse shear deformation in the vibrations of the sandwich plate and cylindrical shell. The effectiveness of viscoelastic damping of vibrations in the sandwich plate and cylindrical shell is investigated through the use of the concept of the damping parameter., Pub. in Non-Classical Shell Problems. Proceedings of the I. A.S.S. Symposium, Warsaw, September 2-5, 1963 p551-71.

Design considerations that influence the selection of materials for rocket-motor cases are discussed. The main intent is to clarify considerations of design for the benefit of the materials specialists in the aerospace industry and for the benefit of the materials industries which supply the aerospace industry. A brief discussion is given of types of missiles and mission profiles. This is followed by a discussion of the external and internal loads and environment to which the missile is subjected. The mechanical and thermal loads are reacted by the motor case acting as a structure; hence, a discussion of stresses and other design factors is included. Next, structural safety and reliability are discussed from a design point of view. The following aspects of basic material behavior are discussed in relation to motor-case design requirements: static mechanical behavior, fatigue behavior, thermal effects, and other environmental effects. In order to provide realistic criteria for materials selection, design for minimum weight is presented from the material- index point of view. Considerations not related directly to design, for example, producibility, cost, and corrosion resistance, are not included.

Large crystals of alpha-SiC have been grown from solution in chromium by the traveling solvent method at an average temperature of ca. 1800 C. The major problem has been the proper wetting of the SiC surface by chromium; this problem has not been solved using an ultrahigh vacuum heating treatment, followed by the evaporation of chromium onto the clean surfaces. Preliminary experiments using silicon and platinum as solvents have shown encouraging results.

Contents: Behavior of fuels and lubricants in dynamic test equipment operating in the presence of gamma radiation; Development of nuclear radiation resistant solid film lubricants; Intereffects between reactor radiation and MIL- L-7808C aircraft turbine oil; Development of radiation resistant high-temperature lubricants; Electrical effects of high-intensity ionizing radiation on nonmetals; Study of radiation effects on electrical insulation; Radiation effects on fuel tank sealants and bladder cell material; Effect of electron radiation on the complex dynamic modulus of polystyrene and high density polyethylene; Radiation resistant silicones; Radiation effects on organo- silicons; Effects of gamma radiation on fluorocarbon polymers; Fast neutron activation of seaplane material (This paper is classified and is bound in Volume Six); Effects of nuclear radiation on cork, leather, and elastomers; ''Plate shear method'' of determining the modulus of rigidity of sandwich panels; ''O'' ring testing in a mixed field irradiation; Radiation effects on 23 silicone rubbers at radiation environment due to activation and scattering effects near based seaplanes.

The dynamically similar structural model of the preceding contract (See AD-416 784) was redesigned and reworked to improve the simulation. The sandwich structure simulation, the backing board simulation, the intake ducting simulation were improved. Some previously discovered errors in simulation were corrected. The reworked model was then Vibroacoustically tested. The results of this testing were compared to the results of the actual fuselage portion testing of the previous contract. The model was modified to obtain a dynamically similar structural model of the complete XSM-62 Snark missile. The Acoustic (noise) Test Program that was performed on the XSM-62 Snark missile during the design and development of the Snark missile program was duplicated for the model. The model test data was compared to the results of the missile test program. This was done to show the feasibility of such a dynamic modeling method for design of future missile and space vehicle systems., Report on Dynamic Problems in Flight Vehicles.

A description is given of the fabrication studies and tests to determine the material allowables for, together with a description of, subscale and full-scale filament- o nd sandwich rocket motor cases. The edgewise compression and smallscale sandwich-wall cylinder tests that were initiated to determine design values for sizing the subscale and full-scale sandwich rocket motor cases are summarized. The fabrication process used to build the sandwich- wall cylinders and subscale cases is described in detail, together with the associated mandrel-tooling development studies. Test results of the subscale motor cases are discussed and analyzed. A subscale case was built which exceeded the ultimate design pressure by 10 percent. A detailed stress analysis for the full-scale rocket motor cases is presented, together with design drawings of the motor case, nozzle, and internal insulation.

An attempt was made to establish the correlation between surface waviness of honeycomb core panels and the face wrinkling attendant upon the panels when subjected to compressive forces. Tests were conducted with honeycomb sandwich edgewise compression specimens with controlled initial surface waviness.

Chromium alloys, Cobalt alloys, Molybdenum alloys, *Titanium alloys.) Identifiers: Alloys compilation. The information contained in this report consists primarily of previously unpublished mechanical property data on some engineering materials. Although mechanical property data is of primary concern, there is some information presented on physical properties. Materials covered are adhesives, Al, braze alloys, fiberglas, Inconel, laminates, Mo, pneumatic seals, Rene' 41, sealants, steel, super alloys and Ti. (Author)

A theoretical analysis of axisymmetric elastic deformations and stresses in a web-stiffened sandwich cylindrical shell structure under external hydrostatic pressure is presented. The solution is based on the use of edge coefficients for plate and shell elements of finite length, and includes the computation of edge forces and moments arising at common junctures of these elements. Equations are given for computing numerically the longitudinal and circumferential stresses in the two coaxial cylindrical shells and the radial and tangential stresses in the web stiffeners between the two shells. No consideration was given to the discontinuity effects arising from rigid or elastic restraints afforded by contiguous bulkhead or adjacent shell structures. Thus, the analysis presented is applicable only to a typical bay of a web- stiffened sandwich cylinder of long length. A numerical example is presented to illustrate the use of the equations.

This volume is volume 2 of four volumes and summarizes the portion of the program concerned with the fabrication, testing, and analysis of basic element specimens composed partially or entirely of the boron/epoxy advanced composite material. The main body of this volume comprises independent sections devoted to the topics: fabrication of basic structural elements; testing of basic structural elements; and analysis of tests on unstiffened skin, honeycomb sandwich, and stiffened skin., See also Volume 3, AD878221.

The report, the second part of a series giving data for design against acoustic fatigue, has been prepared in order to draw together the results of research in acoustic fatigue and to present them in a form directly useable in aerospace design. Future work in this series will deal with endurance of titanium alloy structures under simulated acoustic loading, near field compressor noise estimation, stress response of box and control surface structures, structural damping and stress response of skin-stringer panels with stringers of relatively low flexural stiffness., Includes errata sheet for Part 1 dated May 1972. See also Part 1, AD744210. NATO furnished.

The report describes the continuation of an investigation into the use of sandwich construction in glass reinforced plastics (GRP) for load bearing ship structures. For these applications, the primary interest is in comparatively cheap woven cloth or woven rovings for the skins, with a variety of lightweight materials for the core. The relevant stiffness and strength characteristics of various sandwich constructions were examined by means of tests applying lateral loads to beams manufactured to typify the various sandwich constructions considered for this purpose. The constructions used 'Plasticell' and BAP 'flomat' box cores. The investigation was carried out with regard to static loading only, and effects due to fatigue, shock and high temperatures were not considered.

Topics included are: Aluminum; Nickel and Superalloys; Beryllium.

The preliminary results of a joint industry-government research project are described for static tests of a fixed-edge, stiffened boat structure of glass-reinforced plastic (GRP) sandwich construction. The measured stresses and deflections are compared with predictions of panel response.