Vacuum Balloon–A 350-Year-Old Dream

The centuries-old idea of a lighter-than-air vacuum balloon has not materialized yet as such structure needs to be both light enough to float in the air and strong enough to withstand atmospheric pressure. We propose a design of a rigid spherical sandwich shell and demonstrate that it can satisfy these stringent conditions with commercially available materials, such as boron carbide ceramic and aluminum alloy honeycomb. A finite element analysis was employed to demonstrate that buckling can be prevented in the proposed structure. Also discussed are other modes of failure and approaches to manufacturing.

Residual compressive strength of aluminum alloy honeycomb sandwich panel in the presence of multiple impact dents

The present article discusses the effect of impact damage on residual compressive strength of aluminum alloy honeycomb sandwich panel (HSP). Multiple dents were created in HSP by penetrating indenters of different diameters through quasi-static indentation technique. The damaged samples were compressed edge-wise for determination of in-plane compression after impact (CAI) strength. The failed samples were macroscopically examined to reveal the underlying damage mode. Experimental results showed that the presence of multiple dents of 5 mm size or less do not appreciably affect the CAI strength of aluminum alloy HSP. However, moderate reduction in CAI strength was observed in case of multiple dents of 10 mm. Compressive strength was reduced by 18% in presence of four dents of 10 mm diameter. The maximum reduction in CAI strength of up to 30% was observed in samples impact damaged by 15 mm indenter. Examination of failed HSP showed that the maximum load was sustained taken by aluminum facesheet whereas the contribution of honeycomb core was insignificant. Research findings exhibit that the CAI strength of aluminum alloy honeycomb structure is not sensitive to impact damages size less than 5 mm diameter however dents above 5 mm size can seriously impair mechanical performance and structural integrity.

Investigation of Energy Absorbed by Composite Panels with Honeycomb Aluminum Alloy Core

The aim of this study was to measure the energy absorbed by composite panels with carbon fiber-reinforced polymer (CFRP) skins and a 5052 aluminum alloy honeycomb core and to compare it to previous research and isotropic material—two 25 × 1.75 mm 1.0562 alloy steel tubes. The panel skins layup consisted of pre-impregnated Pyrofil TR30S 210 gsm 3K 2 × 2 twill oriented in directions 0/90 and −45/45 and having a consolidated thickness of 1 mm or 2 mm. The core consisted of a 15 mm or 20 mm honeycomb oriented along its lengthwise direction. The first test consisted of a three-point bending of specimens supported at a span of 400 mm with a 50 mm radius tubular load applicator in the middle. Second, a perimeter shear test was conducted using a 25 mm diameter punch and a 38 mm diameter hole. The results of the three-point bending test show that the energy absorbed by panels with 1 mm skins was similar to the energy absorbed by the tubes (96 J), which was better than the previously considered panels. In the case of perimeter shear, the average maximum forces for the top and bottom skin were 5.7 kN and 6.6 kN, respectively. For the panel with thicker skins (2 mm), the results were about 2 times higher.

Connection Performance of Bolted Aluminum Alloy Honeycomb Panel-Beam Composite Structure

A convenient and reliable connection between panels and beams was investigated for collaborative work of single-layer composite reticulated shell structure in which aluminum alloy honeycomb panels participate. In the paper, the "self-tapping bolt" connection was adopted to realize the "tight fit" performance of connection effectively in the composite structure. Through three groups of bearing capacity test on 1.5 m×3 m square meters of the aluminum alloy honeycomb panel-square tube beam combined structure, the force characteristics and failure mechanism of the structures were studied. The experimental results revealed that the connection method could ensure effective transmission between the panel and the beam which made them work in excellent condition. In order to simulate complex performance connection with the panel-beam composite structure, tangential and normal contact behavior were considered at the bolt connection point between the honeycomb panel and the beam in ABAQUS analysis. The analysis results illustrated that the finite element results had the highest matching degree with the experimental values when the friction coefficient of the joint boundary was 0.25. The finite element analysis of the connection bolts spacing indicated that the economic and excellent connection effect can be achieved when the spacing was about 90 mm.

Cold Extrusion Forming Aluminum Alloy Honeycomb Radiator Mold Structure Optimization

The quality of the honeycomb radiator structure has a great impact on thermal performance of the LED lamp. In order to make honeycomb radiators structure more uniform and materials fluidity much better; we firstly take use of cold extrusion to form the honeycomb radiator, then it will be machined. In the honeycomb radiator deformation than the larger places where prone to stress concentration, that has a seriously affect on the effect of the radiator forming. Therefore, we optimized the extrusion die, including upper and lower mold prone to stress concentration places create fillet. The results show that an appropriate fillet of the mold can greatly improve the forming uniformity and reduce the force on the die.

The Research of Aluminum Alloy Honeycomb Sandwich Panel Mechanical Properties in Out-Plane Compression Test

This paper first studied aluminum alloy honeycomb sandwich panel in out- plane static compress test.Through analyzing deformation characteristics, the loads-displacement relationship was obtained and are described by the average stress-strain curve. Secondly, using the Split Hopkinson Pressure Bar device of impact test, deformation behaviour，dynamic average stress-strain curve data and so on were got under different loading rates, thus learned impact dynamics characteristics of that.