Autoclave tooling

For thermal protection during reentry from space, Dornier manufactured some model shingles from SiC/SiC and C/SiC. Fig. 13 shows two shingles each reinforced with two beads. For these parts a special prepreg was developed which had a 2.5 D fiber structure and enabled easy forming by autoclave tools to be carried out. 

Inoculation tools not sterile. Autoclave tools, soak in alcohol, flame sterilize before using. 

Autoclave tools are massive and produce often a very high carbon emission during the production of their source materials (e.g., aluminum). 

Fig. 18 shows a trio of autoclaves. In the foreground is a bond assembly on a wheeled tool ready to be placed in the autoclave. A technician stands at a control console next to a two-level rack used for holding multiple bond tools in the autoclave. 

Fig. 18. Autoclaves and bond tools. Reproduced by permission of the Boeing Company.

The thermal mass of parts and tools and the heating capacity of the autoclave naturally limit the maximum heating rate. Attempting to increase the heat-up rate by overheating the autoclave air can result in overheating of areas of the assembly with low thermal mass. 

First part qualification. First part qualification is a process performed the first time a new bonded assembly is manufactured or the first time a new tool is used to manufacture a bonded assembly. First part qualification provides assurance that all of the aspects that control bond assembly quality, such as the design dimensions, detail part manufacturing techniques, tool dimensions, layup procedures and autoclave cure cycle parameters are correct and will produce a bond assembly that meets the engineering requirements. 

The first type of bonded design for this application was the beaded doubler panel (Fig. 28). This design was fairly successful at addressing the problems with simple riveted structure but had two primary drawbacks. The area under the beads remained a single thickness sheet and was still prone to fatigue. Reducing the unbonded areas under the beads was not a solution because it reduced the overall stiffness of the panel. Secondly, tooling for these panels was complex and not very robust. Autoclave pressure applied to the beaded areas of the doubler would cause them to collapse, so thick frames were fabricated with cutouts for the beads to protect them. A rubber layer bonded to the surface of the frames... 

VG Extruded, injection molded, thermo-formed and machined Autoclavable surgical tools, coil forms, pump housings, valves, pipe... 

For higher pressures, autoclaves are in common use by organic chemists. As tools for reactor scale-up, most commercial autoclaves show significant deficiencies ... 

The part sizes are limited by the tool sizes such as moulds, dies, autoclaves or winding machines and by the power and the size of equipment such as presses, bags, pultrusion machines, etc. 

Figures 10 and 11 show a manufacturing application in which a resin s flow properties are measured in-sltu at a particular point in a thick laminate during cure in an autoclave. The sensor was inserted on the tool surface and in the center of a thick 192 TGDDM graphite epoxy laminate. Figure 10 shows the noise free raw data taken by the center sensor during cure in the 8x4 foot production size autoclave. Using the procedures described, the ionic mobility was measured at both the tool surface and the center of the thick laminate. In Figure 11, the sensor values of a show a 10 to 20 minute time lag in the point of maximum flow on the surface versus the laminate s center. Measurements of a versus q, as shown in...

Figure 4.15 shows the results from such a sensor controlled run in an autoclave. FDEMS sensor-measured viscosities from two sensors at the center ply and one sensor at the surface ply are shown in Figure 4.15. Air autoclave temperatures and the temperatures at the surface and center ply are also shown. The starting time for the FDEMS sensor-controlled autoclave run and the manufacturer s cure cycle run are defined as file time at which the tool surface temperature starts to increase.

Resin flow and pressure distributions are among the most challenging aspects of the autoclave process cycle to model. Accounting for tooling and bagging variations, such as inner bag... 

Although debulking is routinely conducted at room temperature using vacuum pressure, hot debulking in an autoclave is sometimes required to sufficiently reduce the bulk factor when close tolerance matched die tools are used (i.e., the tool will not fit together unless the bulk factor is reduced to near final dimensions). It is unfortunately a nuisance to debulk every part every several plies and it can dramatically increase the collation costs. A trade-off between part quality and production cost must once again be made in a logical manner. 

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