|
|
|
Carbon Fiber Support Structure
|
|
The main structure consists of a hexagonal tube 19.5 inches corner to corner across the base and 29 inches tall as shown in figure 1. The bottom is open and there is a mid deck and top deck, both ~ 1 inch thick. On each deck, two of the sides are ‘open’ while the other four have an ‘X’ stiffener across the side opening. The ‘open’ sides are rotated by one wall section from the lower to the upper section to increase the stiffness of the finished structure.
The sides as shown in figure 1 are composed of Graphite/Epoxy (Gr/E) sheets cut and laminated to form open frames or frames with an ‘X’ through the center. The basic Gr/E sheet is composed of 5 fabric layers in a [0, +45, 0, +45, 0] lay-up to produce a finished bonded sheet with quasi-isotropic properties. These side panels are ~ 0.45" thick and are composed of two 0.041" thick 5 layer Gr/E sheets separated by a 0.375" wide 0.041" thick stiffener sheet. Each side wall was prepared, glued and cured as a separate piece.
The two deck sections are composed of two Gr/E sheets separated by a 1.000" thick layer of KOREX honeycomb lattice. The KOREX-Gr/E were bonded using Cytol Film and then thermally cured. Six 10-32 screw inserts were placed into both faces of the mid deck, and in one side of the top deck to facilitate attachment of experimental equipment into the structure. After curing the decks were cut to their final hexagonal form.
The walls and decks were attached to corner posts of Gr/E pultruded 120º angle sections 29" long. All wall-corner joints were bonded using HYSOL 9394 epoxy, an aerospace qualified epoxy.
Aluminum stiffeners were potted in the bottom 120º corners and aluminum 90º angle brackets were potted into the bottom edge of the structure for mounting to a base plate. These Aluminum-Gr/E joints were made using HYSL 9394. For added security, the bottom 90º angle brackets are also attached using 3 rivets along each wall edge. The bottom 90º angle brackets have 10-32 thru clear holes to match a 19.5" diameter circle of 24 equally spaced holes.
The Gr/E-Gr/E lap joints have been tested and shown to have a maximum shear stress of 1010 psi. The Gr/E-Aluminum joints were tested and determined to have a maximum shear stress of 550 psi.
|
|
|