isogrid

File:Isogrid topview.png

[[File:Isogrid flange.png|thumb|baseline|alt=|Cross-section of isogrid flange stiffener{{cite patent

| country = US

| number = 4012549

| status = patent

| title = High strength composite structure

| pubdate = Oct 10, 1974

| gdate = Mar 15, 1977

| fdate = Oct 10, 1974

| inventor = Paul Slysh

}}

]]

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.{{Cite journal |date=2016-05-20 |title=Design and manufacturing of an isogrid structure in composite material: Numerical and experimental results |journal=Composite Structures |language=en |volume=143 |pages=189–201 |doi=10.1016/j.compstruct.2016.02.043 |issn=0263-8223 |last1=Sorrentino |first1=L. |last2=Marchetti |first2=M. |last3=Bellini |first3=C. |last4=Delfini |first4=A. |last5=Albano |first5=M.}}

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.

{{cite tech report

|url=https://femci.gsfc.nasa.gov/isogrid/NASA-CR-124075_Isogrid_Design.pdf

|title=Isogrid Design Handbook

|author=McDonnell Douglas Astronautics Company

|date=February 1973

|publisher=NASA

|number=NASA CR-124075

|access-date=Jan 10, 2020

|page=1.0.002 (12/252)}}

{{cite book

|last1 = Meyer | first1 = R. R

|last2 = Harwood | first2 = O. P.

|title = Isogrid design handbook

|publisher = Marshall Space Flight Center

|date = Oct 1, 1973

|orig-year = 1973

|url=https://ntrs.nasa.gov/search.jsp?R=19730000395&qs=Ns%3DNASA-Center%7c0%26N%3D4294753258

|id=19730000395

}}

{{anchor|Orthogrid}}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.

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 {{convert|0.04|in|mm}} might require chemical milling processes.{{cite web

| url = http://www.isogrid-sst.com/machine%20design.htm

| archive-url = https://web.archive.org/web/20120324153516/http://www.isogrid-sst.com/machine%20design.htm

| archive-date = March 24, 2012

| url-status = live

| title = The Isogrid

| first = Paul

| last = Slysh

| access-date = May 27, 2011

}}

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.{{Cite web |author1=K. Tripathi |author2=K. Kukreja |author3=A. K. Madan |title=Evolution in Manufacturing of Grid Stiffened Structures through CAM and Additive Techniques |url=https://www.researchgate.net/publication/351065515 |website=Research Gate}}

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.{{cite journal

| last = Huybrechts

| first = Steven

| author2 = Troy E. Meink

| author3 = Peter M. Wegner

| author4 = Jeff M. Ganley

| title = Manufacturing theory for advanced grid stiffened structures

| journal = Composites Part A: Applied Science and Manufacturing

| volume = 33

| issue = 2

| pages = 155–161

| publisher = Elsevier

| year = 2002

| url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA430878

| archive-url = https://web.archive.org/web/20160304055254/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA430878

| url-status = dead

| archive-date = March 4, 2016

| access-date = 26 May 2012

| doi = 10.1016/S1359-835X(01)00113-0

}}

This can give extremely high strength-to-weight ratios.{{Cite conference

| last1 = Wegner | first1 = Peter M.

| last2 = Higgins | first2 = John E.

| last3 = VanWest | first3 = Barry P.

| title = Application of Advanced Grid-Stiffened Structures Technology to the Minotaur Payload Fairing

| book-title = 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

| place = Denver, CO

| year = 2002

| url = http://handle.dtic.mil/100.2/ADA510804

| archive-url = https://web.archive.org/web/20120527163248/http://handle.dtic.mil/100.2/ADA510804

| url-status = dead

| archive-date = May 27, 2012

}}

File:CST-100 pressure vessel.jpg 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|date=September 2024}}

Some spacecraft and launch vehicles which use isogrid structures include:

• Delta families{{Citation

|last = Knighton

|first = D. J.

|title = Delta launch vehicle isogrid structure NASTRAN analysis

|journal = Nastran: Users' Experiences

|publisher = Goddard Space Flight Center

|date = Sep 1, 1972

|orig-year = 1972

|hdl = 2060/19720025227

|url = https://ntrs.nasa.gov/search.jsp?R=19720025227

|archive-url = https://web.archive.org/web/20210129191829/https://ntrs.nasa.gov/search.jsp?R=19720025227

|archive-date = January 29, 2021

|access-date = July 7, 2017

|url-status = bot: unknown

}}

• Atlas families{{Cite web|url=http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf|title=Atlas V 500 series|publisher=United Launch Alliance|access-date=2016-06-06|archive-url=https://web.archive.org/web/20160409203927/http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf|archive-date=2016-04-09|url-status=dead}}
• Skylab spacestation Orbital Workshop module
• SLS Core Stage{{cite web

|url=https://www.spacelaunchreport.com/sls7.html

|archive-url=https://web.archive.org/web/20140404120940/http://spacelaunchreport.com/sls7.html

|url-status=usurped

|archive-date=April 4, 2014

|title=Progress on NASA's Space Launch System and Orion

|last= Kyle

|first= Ed

|date=Jan 26, 2014

|website=Space Launch Report

|access-date=Jan 10, 2020

|quote=Boeing's SLS core will use AL-2219 Aluminum machined with isogrids}}

• CST-100 Starliner{{cite news|last1=Young|first1=Anthony|title=Boeing displays CST-100 progress at Kennedy Space Center|url=http://www.thespacereview.com/article/2538/1|access-date=25 October 2017|work=The Space Review|publisher=SpaceNews|date=23 June 2014}}
• Spacex Crew Dragon{{Cite web |last=Editor |first=SpaceRef |date=2010-10-05 |title=SpaceX Update: COTS Demonstration Flight 1 (with photos) |url=https://spaceref.com/status-report/spacex-update-cots-demonstration-flight-1-with-photos/ |access-date=2022-11-03 |website=SpaceRef |language=en-US}}

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

• Saturn rocket tanks, due to the lower cost and ease of manufacture{{Citation

| last = Wagner

| first = W. A.

| title = Liquid rocket metal tanks and tank components

| publisher = NASA Lewis Research Center

| date = May 1, 1974

| orig-year = 1974

| hdl = 2060/19750004950

| pages = 55–58

| url = https://ntrs.nasa.gov/search.jsp?R=19750004950

| archive-url = https://web.archive.org/web/20210130173055/https://ntrs.nasa.gov/search.jsp?R=19750004950

| archive-date = January 30, 2021

| access-date = November 26, 2019

| url-status = bot: unknown

}}

• Vulcan rocket{{cite tweet |last=Bruno |first=Tory |user=torybruno |number=855031915270635522 |date=Apr 20, 2017 |title=Orthogrid trial panel for Vulcan Rocket propellant tank. (Bigger than it looks...) |link=https://twitter.com/torybruno/status/855031915270635522 |access-date=Jan 10, 2020}}
• New Glenn rocket tanks
• Space Launch System core stage tanks

{{Clear}}

• Honeycomb structure
• Hollow structural section
• Space frame
• Speed holes
• Truss
• Waffle slab, concrete structure similar to orthogrid

{{clear}}

{{Reflist}}

• [http://femci.gsfc.nasa.gov/Isogrid/ Isogrid Plate Modeling, Dr Wiliam Case, 1997]
• [http://femci.gsfc.nasa.gov/Isogrid/NASA-CR-124075_Isogrid_Design.pdf Isogrid Design Handbook, NASA CR-124075, McDonnell Douglas, 1973]
• [http://composite.about.com/library/weekly/aa980525.htm Advanced Grid Stiffened Composite Structures] {{Webarchive|url=https://web.archive.org/web/20060422101203/http://composite.about.com/library/weekly/aa980525.htm |date=2006-04-22 }}
• [http://Isogrid-SST.com/referenc.htm Isogrid - Shell Structures Tools, 1990] {{Webarchive|url=https://web.archive.org/web/20110713063212/http://isogrid-sst.com/referenc.htm |date=2011-07-13 }}
• [http://www.sheldrake.net/quarter_isogrid/ Quarter Isogrid used in Surfboard Construction]

{{commonscat|Isogrid}}

{{Authority control}}

Category:Components

Category:Aerospace materials