Showing papers on "Sandwich-structured composite published in 1977"

A New Static Compression Fixture for Advanced Composite Materials

Abstract: Advanced composite compressive data are generally less abundant than the corresponding tension data for the same material. There are two reasons for this paucity of data: (1) the difficulties associated with compressive testing of specimens prepared from thin sheets of advanced composite materials such as end splitting, buckling of the specimens, and load alignment problems; and (2) the expense associated with generally accepted workable but complex specimens such as the sandwich beam compressive specimen. This paper describes a method of compression testing of specimens which alleviates the problem areas described above. In addition, several associated areas which are adjunct to the method such as elevated temperature testing are also reported and detailed. Basically, a fixture with linear, nearly frictionless bearings is employed with a straight-sided tab-ended specimen to determine compressive strength, yield, ultimate strain, modulus, and Poisson's ratio. A comparison is made with the test results of other methods. Finally, recommendations for additional improvement on this fixture are set forth.

Noise transmission by viscoelastic sandwich panels

Abstract: An analytical study on low frequency noise transmission into rectangular enclosures by viscoelastic sandwich panels is presented. Soft compressible cores with dilatational modes and hard incompressible cores with dilatational modes neglected are considered as limiting cases of core stiffness. It is reported that these panels can effect significant noise reduction.

Thermal Stresses and Deflection of Sandwich Panels

Abstract: Sandwich panels with foamed cores and cold-formed metal faces are becoming more and more popular as building enclosures. It is not unusual that the temperature difference between the inside and outside wall surfaces may exceed 100°F. Experimentally, full-sized sandwich panels of different profiles were placed in a heat chamber in single and double spans. One side of the panel was subject to the heat flux generated in a heat chamber, whereas the other side was at room temperature. Special precaution was taken so that the temperature inside the heat chamber was uniform. Thermistors were used to detect the surface temperature of the panel. Strain and dial gages were also used. Formulated as an ordinary fourth-order differential equation, using suitable boundary conditions, expressions were derived for deflection, flexural stresses in the facings, and shear stresses in the core. Using the method of consistent deformations, similar expressions were derived for multiple spans.

Rafterless building roof construction - is of sandwich panels with thin, load:resistant layers enclosing thick foam one

Abstract: The rafterless building has a roof, typically of the saddle type, sloping downwards on both sides of a ridge. The roof is of sandwich panels, these each comprising a relatively thick plate (10) of very light cohesive material such as plastic foam or perlite, glued on the inner and outer surface all over to a thin layer (11, 13) absorbing the tension and compression loads, being much stronger and resistant to tension than the thick layer. The thick plate joins the thin inner and outer layers together to form a cohesive bending beam. Near the lower ends the panels can be supported at two points (7, 8) spaced apart in a direction at right angles to the building wall (4).

Method of making a composite sandwich lattice structure

Abstract: This invention relates to a lattice type structural panel utilizing the unidirectional character of filamentary epoxy impregnated composites to produce stiff lightweight structural panels for use in constructing large area panels for space satellites and the like.

Noise transmission by viscoelastic sandwich panels

Abstract: This report presents an analytical study on low frequency noise transmission into rectangular enclosures by viscoelastic sandwich panels. The dimensions of these panels are typical of aircraft fuselage skin constructions. The reportdemonstrates that these panels can effect significant noise reduction. The anal­ysis considers two limiting cases of the core stiffness: (1) soft compressible cores with dilatational modes included and

Sandwich panels using adhesive construction - with simultaneous adhesive coating of top and bottom cover panels

Abstract: The method for mfr. of sandwich panels for construction is carried out by coating the bottom cover panel (10) with a layer of adhesive and with the optional multi-layer core (12), and at the same time coating the upwardly facing inner surface of the top cover panel (11) with a layer of adhesive, then turning the top cover panel (23) to deposit it on the core. The cover panels are pref. coated simultaneously during conveyance on separate parallel conveyor paths (13). The top cover panels may rest on a roll train (27) in the region of the turning device which has pivot arms (24) directed between the rolls (28) of the roll train in the starting position.

Damage Tolerance of Thin Skin Sandwich Panels.

Abstract: : An instrumented test procedure for low energy impact tolerance of thin skin sandwich panels was developed. Damage modes of this test were shown to correlate on a one-to-one basis with actual falling ball tests. Basic parameters of core density, cell size, skin thickness, and fiber orientation were examined and results useful to designing of sandwich panels are discussed. (Author)

The minimum weight design of compression structures including plasticity effects

Abstract: The minimum weight design of a wide range of structures required to resist compressive loading is considered. Items which have been analysed in detail include struts of various sorts, thin plates, honeycomb core sandwich panels, wide column stiffened panels, stiffened panels with optimised support locations, and cylindrical shells stiffened by axial stiffners and rings. A further study is concerned with the effects of imperfections on a tower with corrugation stiffened walls, loaded in compression. - Except for the corrugated tower, each analysis includes the effects of plasticity in a direct and realistic way by characterising stress-strain behaviour in the manner suggested by Ramberg and Osgood. Results for each type of structure are presented, together with the appropriate computer programmes.

Fabrication and evaluation of advanced titanium structural panels for supersonic cruise aircraft

Abstract: Flightworthy primary structural panels were designed, fabricated, and tested to investigate two advanced fabrication methods for titanium alloys. Skin-stringer panels fabricated using the weldbraze process, and honeycomb-core sandwich panels fabricated using a diffusion bonding process, were designed to replace an existing integrally stiffened shear panel on the upper wing surface of the NASA YF-12 research aircraft. The investigation included ground testing and Mach 3 flight testing of full-scale panels, and laboratory testing of representative structural element specimens. Test results obtained on full-scale panels and structural element specimens indicate that both of the fabrication methods investigated are suitable for primary structural applications on future civil and military supersonic cruise aircraft.

Effect of temperature on composite sandwich structures subjected to low velocity impact

Abstract: The effect of low velocity projectile impact on sandwich-type structural components was investigated. The materials used in the fabrication of the impact surface were graphite-, Kevlar-, and boron-fibers with appropriate epoxy matrices. The testing of the specimens was performed at moderately low- and high-temperatures as well as at room temperature to assess the impact-initiated strength degradation of the laminates. Eleven laminates with different stacking sequences, orientations, and thicknesses were tested. The low energy projectile impact is considered to simulate the damage caused by runway debris, the dropping of the hand tools during servicing, etc., on the secondary aircraft structures fabricated with the composite materials. The results show the preload and the impact energy combinations necessary to cause catastrophic failure in the laminates tested. A set of faired curves indicating the failure thresholds is shown separately for the tension-and compression-loaded laminates. The specific-strengths and -modulii for the various laminates tested are also given.

Eccentrically loaded sandwich panels

Abstract: The paper deals with the design of eccentrically loaded sandwich panels in civil engineering structures. A theoretical analysis taking into account the non-linear stress–strain properties of the materials and the influence of shear deformations is proposed. A computer program based on the described algorithm is used to solve a numerical example. It is found that the Newton–Raphson procedure both in the solution of strains at individual sections and in the step by step procedure over the whole structure converges rapidly. Thus the method is suitable for the evaluation of the critical load due to strength failure or loss of stability.