A simple change in the design of tools used in manufacturing laminated-composite-material sandwich panels reduces the floor area needed to store the tools. To give meaning to a description of this modification, it is necessary to explain the basic function and original design of these tools: The basic function of such a tool is to provide a surface sized and shaped (possibly including a complex curvature) to match one of the two face sheets of the composite sandwich panel to be fabricated. A sheet of laminated composite material in uncured or partially cured form is laid up on the tool surface, then cured to form a face sheet (see Figure 1). The face sheet is then removed from the tool surface. The opposite face sheet is formed in the same manner on another tool, then the two face sheets are bonded to opposite faces of a honeycomb- or eggcrate-like core to form the composite sandwich panel.
Often, tools of this type have structures similar to those of the composite panels to be fabricated; the tools can include face sheets that define the tool surfaces and that are supported by honeycomb- or eggcrate-like structures. Often, the tools are even made of composite materials.
Each tool designed according to the original concept described thus far includes only one tool surface. The modified-tool concept calls for two tool surfaces for forming both face sheets of the composite sandwich panel that one seeks to fabricate. Like the panel itself, the tool of modified design features two face sheets (which define the two tool surfaces) bonded to opposite faces of a honeycomb- or eggcrate-like core (see Figure 2). To facilitate handling, the tool can be mounted in a steel frame; the mounting should be loose, with sufficient clearance to allow the tool to "float" in the frame to accommodate differential thermal expansion between the tool and the frame.
The biggest advantage of the two-sided tool design over the single-sided tool design is that twice as much mold-surface area is accommodated in the same floor area — an important consideration in the manufacture of large panels. In addition, the fabrication of two tool faces held on a common supporting structure involves less labor than does fabrication of two tool faces on individual supporting structures. The two-sided tool design could prove useful in the manufacture of a variety of curved composite-material sandwich parts; for example, boat hulls and outer shells of automobiles.
This work was done by David Altemir and Mike Fowler of Johnson Space Center.No further documentation is available.