Isogrid

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Isogrid on the interior of the adapter connecting the Orion spacecraft to the Delta IV rocket for Exploration Flight Test 1

Isogrid is a type of partially hollowed-out structure formed usually from a single metal plate with integral triangular stiffening stringers. It was patented by McDonnell Douglas (now part of Boeing) in 1975.[1][2] Isogrids are extremely light and stiff.[3] Compared to other materials, it is expensive to manufacture, and so it is restricted to spaceflight applications and some aerospace use.[citation needed]

Theory and design

Top view of isogrid panel
Cross-section of isogrid flange stiffener[4]

Isogrid structures are related to sandwich-structured composite panels; both can be modeled using sandwich theory, which describes structures with separated, stiff face sheets and a lighter interconnecting layer. Isogrids are manufactured from single sheets of material and with large-scale triangular openings, and an open pattern to the flanges, compared to closed sheets and foam or honeycomb structures for the sandwich-composite structures.

Isogrid structures are constituted by a thin skin reinforced with a lattice structure. Such structures are adopted in the aeronautical industry since they present both structural resistance and lightness.[5]

The term isogrid is used because the structure acts like an isotropic material, having the same properties along any axis. Traditionally, the equilateral triangle pattern was used because it was amenable to simplified analysis.[6][7] A variant is the orthogrid (sometimes called a waffle grid), which uses rectangular rather than triangular openings. It is not isotropic (has different properties in different orientations), but matches many use cases well and is easier to manufacture.

Manufacturing

The stiffeners of an isogrid are generally machined from one face of a single sheet of material such as aluminium with a CNC milling machine. A thickness less than 0.04 inches (1.0 mm) might require chemical milling processes.[8]

A major push has been made toward additive manufacturing techniques due to a decrease in overall material and production costs and high efficiency and accuracy while providing control over parameters like porosity. Also, the ease of prototype manufacturing for testing purposes has made a huge contribution.[9]

Composite isogrids are rib-skin configurations, where at least a part of the rib is a different material from the skin, the composite assembled by various manual or automated processes.[10] This can give extremely high strength-to-weight ratios.[11]

Uses

Isogrids on the CST-100 pressure vessel

Isogrid panels form self-stiffened structures where low weight, stiffness, strength and damage tolerance are important, such as in aircraft or space vehicles. Aerospace isogrid structures include payload shrouds and boosters, which must support the full weight of upper stages and payloads under high G loads. Their open configuration with a single, sealed sheet facing the outside makes them especially useful for propellant tanks for rockets, where sealing the propellant in, but allowing it to drain in use or maintenance are necessary features.[citation needed]

Examples

Some spacecraft and launch vehicles which use isogrid structures include:

Orthogrid

Orthogrid (also known as waffle grid) is similar to isogrid, but with a square pattern; examples include:

See also

References

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  1. ^ Page Template:Citation/styles.css has no content.US4086378A, Kam, Clifford Y.; Freeman, Vernon L. & Penton, Allen P., "Stiffened composite structural member and method of fabrication", issued Script error: No such module "auto date formatter". 
  2. ^ Page Module:Citation/CS1/styles.css has no content.Huybrechts, Steven M.; Hahn, Steven E.; Meink, Troy E. (July 5–9, 1999). GRID STIFFENED STRUCTURES: A SURVEY OF FABRICATION, ANALYSIS AND DESIGN METHODS (PDF). Proceedings of the 1999 International Conference on Composite Materials. Paris, France. Archived from the original (PDF) on December 22, 2019. Retrieved Jan 10, 2020. The McDonnell-Douglas Corporation (now part of The Boeing Company) holds the patent rights for development of the first aluminum isogrid
  3. ^ Page Module:Citation/CS1/styles.css has no content.Black, Jonathan T. (2006). NEW ULTRA-LIGHTWEIGHT STIFF PANELS FOR SPACE APERTURES (PhD). University of Kentucky Doctoral Dissertations. Retrieved Jan 10, 2020.
  4. ^ Page Template:Citation/styles.css has no content.US patent 4012549, Paul Slysh, "High strength composite structure", published Script error: No such module "auto date formatter"., issued Script error: No such module "auto date formatter". 
  5. ^ Page Module:Citation/CS1/styles.css has no content.Sorrentino, L.; Marchetti, M.; Bellini, C.; Delfini, A.; Albano, M. (2016-05-20). "Design and manufacturing of an isogrid structure in composite material: Numerical and experimental results". Composite Structures. 143: 189–201. doi:10.1016/j.compstruct.2016.02.043. ISSN 0263-8223.
  6. ^ a b c Page Module:Citation/CS1/styles.css has no content.McDonnell Douglas Astronautics Company (February 1973). Isogrid Design Handbook (PDF) (Technical report). NASA. p. 1.0.002 (12/252). NASA CR-124075. Retrieved Jan 10, 2020.
  7. ^ Page Module:Citation/CS1/styles.css has no content.Meyer, R. R; Harwood, O. P. (Oct 1, 1973) [1973]. Isogrid design handbook. Marshall Space Flight Center. 19730000395.
  8. ^ Page Module:Citation/CS1/styles.css has no content.Slysh, Paul. "The Isogrid". Archived from the original on March 24, 2012. Retrieved May 27, 2011.
  9. ^ Page Module:Citation/CS1/styles.css has no content.K. Tripathi; K. Kukreja; A. K. Madan. "Evolution in Manufacturing of Grid Stiffened Structures through CAM and Additive Techniques". Research Gate.
  10. ^ Page Module:Citation/CS1/styles.css has no content.Huybrechts, Steven; Troy E. Meink; Peter M. Wegner; Jeff M. Ganley (2002). "Manufacturing theory for advanced grid stiffened structures". Composites Part A: Applied Science and Manufacturing. 33 (2). Elsevier: 155–161. doi:10.1016/S1359-835X(01)00113-0. Archived from the original on March 4, 2016. Retrieved 26 May 2012.
  11. ^ Page Module:Citation/CS1/styles.css has no content.Wegner, Peter M.; Higgins, John E.; VanWest, Barry P. (2002). "Application of Advanced Grid-Stiffened Structures Technology to the Minotaur Payload Fairing". 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Denver, CO. Archived from the original on May 27, 2012.
  12. ^ Page Module:Citation/CS1/styles.css has no content.Knighton, D. J. (Sep 1, 1972) [1972], "Delta launch vehicle isogrid structure NASTRAN analysis", Nastran: Users' Experiences, Goddard Space Flight Center, hdl:2060/19720025227, archived from the original on January 29, 2021, retrieved July 7, 2017{{citation}}: CS1 maint: bot: original URL status unknown (link)
  13. ^ Page Module:Citation/CS1/styles.css has no content."Atlas V 500 series" (PDF). United Launch Alliance. Archived from the original (PDF) on 2016-04-09. Retrieved 2016-06-06.
  14. ^ Page Module:Citation/CS1/styles.css has no content.Kyle, Ed (Jan 26, 2014). "Progress on NASA's Space Launch System and Orion". Space Launch Report. Archived from the original on April 4, 2014. Retrieved Jan 10, 2020. Boeing's SLS core will use AL-2219 Aluminum machined with isogrids
  15. ^ Page Module:Citation/CS1/styles.css has no content.Young, Anthony (23 June 2014). "Boeing displays CST-100 progress at Kennedy Space Center". The Space Review. SpaceNews. Retrieved 25 October 2017.
  16. ^ Page Module:Citation/CS1/styles.css has no content.Editor, SpaceRef (2010-10-05). "SpaceX Update: COTS Demonstration Flight 1 (with photos)". SpaceRef. Retrieved 2022-11-03. {{cite web}}: |last= has generic name (help)
  17. ^ Page Module:Citation/CS1/styles.css has no content.Wagner, W. A. (May 1, 1974) [1974], Liquid rocket metal tanks and tank components, NASA Lewis Research Center, pp. 55–58, hdl:2060/19750004950, archived from the original on January 30, 2021, retrieved November 26, 2019{{citation}}: CS1 maint: bot: original URL status unknown (link)
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