Consolidating touch points for saab
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The necessary design for mechanical fastening complicates the structure, especially in thin sections, because of the need for access to both sides of the bond line. A significant contribution to the total cost is the assembly cost where the precured composite elements are assembled, drilled, and fastened.
These bonds generally have modest strength, and are susceptible to disbanding with shock impact or other “out of plane” forces affecting the assembly.
The reduced thermal mass and ability to focus the heating energy permits change of the operating temperature rapidly which improves the products produced.
Finally, the shop environment is not heated as significantly from the radiation of the large thermal mass of a conventional press.
The bond line lacks any reinforcing material to help with load transfer.
While composites might be adhesively bonded, cocured, or welded, these connecting processes generally produce bonds that rely upon the resin matrix for strength.
Prefabricated composite detail parts use precured strips that include Z-pin reinforcement along the bond line. They are massive, must be heated along with the workpiece, and must be cooled prior to removing the completed part.
Each strip has Z-pin stubble protruding from opposed faces so that the pins are embedded into the detail parts when the joint forms.(a) at least two fiber-reinforced resin composite elements arranged to define a bondline along an interface between the elements, each element being a laminate having a plurality of plies, each ply having fiber reinforcement defining an X-Y plane; (b) a composite strip having cured resin and having X-Y fiber reinforcement, the strip being positioned along the bondline between the elements, the X-Y fiber reinforcement in the strip being confined to the bondline; (c) Z-direction reinforcement extending at least from the strip into one element to reinforce a joint between the strip and that element, the Z-direction reinforcement having an areal density in the range from 0.5-2.0% in the bondline; The present application is a continuation application based upon U. The delay from heating and cooling the mass of the tools adds substantially to the overall time necessary to fabricate each part.
The use of composites in primary structure in aerospace applications is limited today because of their relatively high cost.
These delays are especially significant when the manufacturing run is low rate where the dies need to be changed frequently, often after producing only a few parts of each kind.
Prepregs combine continuous, woven, or chopped reinforcing fibers with an uncured matrix resin, and usually comprise fiber sheets with a thin film of the matrix.
5,935,698, which was a divisional application based upon U. Thermoplastic or thermoset organic resin composites would be more economical if the manufacturing processes reduced touch labor and forming time.
Furthermore, the tooling takes significant time to heat the composite material to its consolidation temperature and, after curing the composite, to cool to a temperature at which it is safe to remove the finished composite part. Designing and making tools to permit their active cooling increases their cost. To ensure an inert atmosphere around the composite during curing and to permit withdrawing volatiles and outgassing from around the composite during the consolidation, they welded the facesheets around their periphery. This “bag-and-seal” technique applies to both resin composite and metal processing. Processing in an Induction Press The dies or tooling for induction processing are ceramic because a ceramic is not susceptible to induction heating and, preferably, is a thermal insulator (i.e., a relatively poor conductor of heat).