Isogrid Plate Modelling

Author: Dr. Wiliam Case, retired
June 1997
Contact: Jeff Bolognese

- Reference: Isogrid Design Handbook - NASA CR-124075, Rev. A, Feb. 1973 - Acrobat icon 8.7MB
   (NASA Technical Report webpage for the design reference.)
- Download the MS Excel spreadsheet ISOGRID.xls - 26KB

An Isogrid panel is a plate (or face sheet) with triangular integral stiffening ribs (often called stringers). The triangular pattern was found to be very efficient because it takes advantage of the fact that triangular trusses are very effecient structures. The term isogrid is used because the structure acts like an isotropic material.

The first figure shows the rib pattern for an isogrid plate. While other types of rib patterns can also be designed, e.g., square or rectangular, the triangular pattern is the only true isogrid.

The figure below shows the top view of a single isogrid cell. The flange is shown as a hidden line through the face sheet. The terms shown are defined as:

    b - rib thickness
    c - flange thickness
    d - rib height
    h - cell height
    t - face sheet thickness
    w - flange width

With these values it is possible to calculate the overall section properties of the isogrid plate and NASTRAN PSHELL input values. The derivation of the necessary equations is not included here. If you are interested in the math, please contact Dr. William Case at the e-mail address provided at the top and bottom of this page.

A Microsoft Excel spreadsheet is provided to calculate the section properties and PSHELL input values. (This spreadsheet will work with Excel versions 5, 6, and 7, and may work with other versions as well.) In the spreadsheet the values shown in the figure below are required (except z, which is called zbar in the spreadsheet).

If you have a plugin that reads Excel spreadsheets, then clicking on the link will launch the plugin; if you want to save the file to your hard drive, then hold down the shift key and click on the link.

Download the MS Excel spreadsheet ISOGRID.xls. (26k)

Dr. William Case, retired
Jeff Bolognese