Showing papers on "Sandwich panel published in 1975"

Impact Damage Tolerance of Graphite/Epoxy Sandwich Panels.

Abstract: The resistance of graphite/epoxy sandwich panels to low energy, foreign object impact damage was studied. Falling weight impact tests were performed on 104 rectangular sandwich panel specimens. The effect of several material, geometry, and loading parameters on damage susceptibility was explored. Damage observed visually was related to residual strength of specimens taken from the impact region, and in some cases, to static indentation tests carried out on companion specimens. Sandwich test specimens were fabricated with face sheets of graphite or S-glass/epoxy with a 1-in. depth nomex honeycomb core. Fiber type, core density, and laminate orientation were fabrication variables. Drop weight tests were accomplished using a 2-in.-diameter steel ball. Initial and residual static shear strength were measured on notched, four-point bend specimens. Impact tests showed that graphite sandwich panels are much more susceptible to foreign object damage than S-glass panels. The impact energy required to sustain the same relative damage level was an order of magnitude greater for the S-glass than for the graphite panels. The failure characteristics observed suggest that this is due primarily to the low strain to failure of graphite composites. Local core crushing occurred in all tests, and all but the S-glass panels suffered fiber fracture and permanent indentation at low energy levels. Core stiffness had an observable effect on impact resistance, but other parameters studied did not appear to significantly affect damage tolerance. An analysis was carried out in which the sandwich panel was represented as an orthotropic sheet on an elastic foundation, and a classical, double Fourier series approach was taken. The load condition was approximated by an influence function technique to effect a constant radius of bending curvature, simulating the region around the drop weight ball. The capability exists to vary the material constants of the face sheet and core to investigate the nature of indentation failure, and to identify factors contributing to impact resistance. Numerical results were obtained for some of the material parameters employed in the impact tests.

Sandwich panel core

Abstract: A core having a repetitive pattern for ribbing comprising triangles and hexagons where each side of any given hexagon is extended pinwheel fashion toward the appropriate side extensions of each of the six adjoining hexagons, all of the hexagons having sides extending to form pinwheels having the same sense, i.e., clockwise or counterclockwise. The triangles are defined by the extensions and are located between the hexagons. Panels using this core are stiff about all axes and do not have an angle of inherent weakness. The core may be stamped, rolled or vacuum-formed out of many materials including paper, cardboard, sheets of various metals and reinforced or thermosetting plastic.

Marine vessel with vertical annular walls

Abstract: A marine vessel for storage or transport of cargo employing a honeycomb sandwich panel system of concrete construction applied to open or closed deck vessels comprising a plurality of vertically extending annular walls formed monolithically with the hull of the vessel in which the vertical annular walls may extend from the bottom deck or slab to the top deck or slab or between either the top or bottom and an intermediate deck or slab with the annular walls defining a plurality of compartments and serving as vertical shear walls which strengthen the structure to withstand stresses caused by wave action and the like in both longitudinal and transverse directions.

Sandwich panel fabrication

Abstract: In the manufacture of sandwich panels, a filler assembly is made up of rib elements and core elements that are roll bonded into a unitary structure, and slices are then cut from the unitary structure forming filler assemblies to be positioned between surface sheets. The surface sheets and the filler assemblies are then bonded together to form the panel.

Evaluation of Adhesive-Bonded Joints in Housing Components of Glass Fiber-Reinforced Polyester Laminate

Abstract: A series of tests was performed on sandwich panel housing components made with glass fiber-reinforced polyester (FRP) laminates. Specifically, long- and short-term tests were performed to evaluate the adhesive bonds between the FRP laminate facings and cores of the panels. Specimens of two different FRP laminates were analyzed and their bonding characteristics with two different adhesives were studied. The test data show that the bond strength was significantly affected by the laminate formulation, adhesive formulation, adhesive thickness, sustained loading, and temperature.

Application of PATCHES-III to the Three-Dimensional Response of Laminated Composite Structures,

Abstract: : A recently developed program for the stress analysis of general solids of composite material is applied in this study to a sandwich panel impact problem and a partially cracked laminate problem Objectives of the study are: (1) to determine the load distribution, the stresses and the deformations in individual plies of these composite laminates and (2) to demonstrate the modeling capabilities and limitations of the PATCHES-III program Preparatory to the analyses, the program was updated to automate the superposition of symmetry - asymmetry subcases for more efficient modeling The present application of the PATCHES-III system to laminated composites was successful in predicting the three-dimensional response of individual plies at very reasonable modeling and computational costs Engineering checks of the overall response with hand calculations using beam and plate models were in good agreement for both the sandwich panel and the partially cracked laminate A modeling error in the boundary conditions for the latter problem introduced fictitious normal forces for the asymmetry subcase These forces were evaluated when the error was discovered and found to be small, on the order of 0015 lbs maximum, and judged not to have a significant effect on the redistribution of load around the crack The constraint force calculations were made possible by a postprocessor data file system developed as one of the objectives of the effort The Experience gained from the present study also indicates the need for improvement in certain areas

Composite building panel with insulating core and metal cover - has internal timber ribs for transmitting shear forces on bending

Abstract: The prefab. sandwich panel has sheet metal covers on both sides between which is placed rigid foam plastics. In addition to the plastic filling the levelling plates are connected internally by timer ribs. The timber internal ribs are adhesive bonded, bolted or riveted to the outside plates which are used especially on building of swimming pools, large refrigerated buildings and air conditioned rooms and tanks. These panels which can be sawn and cut to the required shape and edging material can be fitted readily to the internal timer ribs, the panels can be loaded in bending because the internal timber ribs transmit shear forces on bending and connect the panel side in compression and in tension. The rigid foam core acts as a stabilising member and a spacer and it ensures good thermal and sound insulation.