Honeycomb Structures

Hubble Space Telescope Main Mirror, Honeycomb structure

Hubble Space Telescope Main Mirror, Honeycomb structure

  The Honeycomb structure of the Hubble Space Telescope primary mirror.

The honeycomb shape is used in the design of large telescope mirrors. There are many reasons for this including lightweighting for ease of assembly or to reduce system weight, the stiffness to mass ratio, the reduction in thermal mass which helps reduce the the time delta to thermal equilibrium when the system experiences temperature change and reduces warping of the optical surface from temperature gradients across the mirror. The equilateral triangle, which is used in the construction and architectural industries is stronger but does not beat the hexagonal pattern in terms of stiffness to mass ratio, which in the case of telescopes is critical to optical performance and reducing thermal mass. The Honey-Comb shape is also more desirable in terms stiffness to out-of-plane compression forces and shear forces.

Other applications where we see this shape used in industry are structural design of aircraft and as of late in automobiles such as Audi and BMW, and often see in cardboard packaging. Structural applications typically include a sandwich geometry, where face panels trap the honeycomb material in between and are usually glued, brazed or welded.

The reason this shape is not always used is because of manufacturing cost reasons. These systems are optimized for strength and weight, but at higher cost. So the design engineer or systems engineer must decide what is more important for the end user cost or product performance. Is it acceptable to have a heavier or weaker system that is not optimized but can be more easily manufactured and at lower cost? This is a design study that may be needed or may be obvious for your application.

The honeycomb shape is repeated in nature for similar reasons. Strength to mass ratios in the skull of elephants, packing density in beehives, Cork wood, Carbon60 (Buckminsterfullerene) and carbon nantoubes. What other applications can use this shape for it’s natural advantages?

Find more information at these links:

http://en.wikipedia.org/wiki/Honeycomb_structure

Kepler Primary Mirror, Honeycomb Link to Nasa Image 

Video and article on Nasa’s Orion Mission Heat Sheild Design

http://vimeo.com/67660646

http://courses.ae.utexas.edu/ase463q/design_pages/summer02/nasa/Honeycomb.htm

Post Honeycomb Cereal

ASTM provides testing specifications for testing composites and other structural members in many types of loading conditions. Including:

ASTM D 695 – test method for compressive properties of rigid and reinforced plastics.

ASTM C1424-10 Standard Test Method for Monotonic Compressive Strength of Advanced Ceramics at Ambient Temperature

ASTM C1341-13 Standard Test Method for Flexural Properties of Continuous Fiber-Reinforced Advanced Ceramic Composites

ASTM E9-09 Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature

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NASA Lunar Laser Communications

NASA LUNAR LASER COMM

NASA LUNAR LASER COMMUNICATIONS OPTICAL MODULE, IMAGE COURTESY OF NASA

With all the talk about laser communication these days, here   is a page on what NASA has already been up to in this field.    http://esc.gsfc.nasa.gov/267/271/Space-Terminal.html

Optomechanics

Nikon

Nikon Lens Cross-Section

Opto-mechanical Design is a blog discussing engineering and design of all things related to photonic, optical or relative technologies and innovation.