*4.6.3. Load step 3: curing by thermal conduction*

The final load step in the simulation is to enable the thermal conduction between the bladder and the tool towards the cooler composite laminate (**Figures 13**–**18**).

**Figure 15.** Nodal temperature results at t = 147 s (respective to current load step).

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**Figure 16.** Nodal temperature results at t = 274 s (respective to current load step).

**Figure 17.** Nodal temperature results at t = 338 s (respective to current load step).

**Figure 18.** Nodal temperature results at t = 438 s (respective to current load step).

**Figure 19.** Nodes selected for plotting the temperature gradient throughout the composite material thickness.

Additionally, one element per composite layer was probed to analyze its temperature through time. The selected elements were those in the symmetric center of the composite laminate. The same procedure was used for the bladder, to measure the time required for it to reach its working temperature (**Figures 19**–**23**).

**Figure 12.** Expanded bladder due to applied pressure of 300 psi (the composite plate and tool are in contact).

**Figure 13.** Nodal temperature results at t = 120 s (respective to current load step).

**Figure 14.** Nodal temperature results at t = 130 s, t = 120 s (respective to current load step).

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**Figure 15.** Nodal temperature results at t = 147 s (respective to current load step).

*4.6.2. Load step 2: bladder expansion*

36 Characterizations of Some Composite Materials

plate towards the concave aluminum tool (**Figure 12**).

and the tool towards the cooler composite laminate (**Figures 13**–**18**).

*4.6.3. Load step 3: curing by thermal conduction*

working temperature (**Figures 19**–**23**).

Once the bladder is at operating temperature (285°F), the expansion due to the fluid's pressure is simulated. This makes the bladder expand, which consequently pushes the composite

The final load step in the simulation is to enable the thermal conduction between the bladder

Additionally, one element per composite layer was probed to analyze its temperature through time. The selected elements were those in the symmetric center of the composite laminate. The same procedure was used for the bladder, to measure the time required for it to reach its

**Figure 12.** Expanded bladder due to applied pressure of 300 psi (the composite plate and tool are in contact).

**Figure 13.** Nodal temperature results at t = 120 s (respective to current load step).

**Figure 14.** Nodal temperature results at t = 130 s, t = 120 s (respective to current load step).

**Figure 16.** Nodal temperature results at t = 274 s (respective to current load step).

**Figure 17.** Nodal temperature results at t = 338 s (respective to current load step).

**Figure 18.** Nodal temperature results at t = 438 s (respective to current load step).

**Figure 19.** Nodes selected for plotting the temperature gradient throughout the composite material thickness.

**Figure 20.** Nodes selected for plotting the temperature gradient throughout the composite material thickness.

**Figure 21.** Composite temperature history.

**5. Conclusions**

It can be concluded that both air and water provide similar curing temperatures for the composite laminate, however, the warm-up time is considerably different for the two convective mediums as it can be observed in the above presented results. Air is considerably slower in warming up the silicon bladder up to operating temperature. Once the aluminum tool and the silicon bladder are at operating temperature, the bladder thickness nor the convective medium have much effect on the overall curing process time. It is only until the very end that

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Based on results of the simulation provided, the use of a snap cure epoxy binder, and an additional 90 second cycle to cool the part; It seems highly probable that parts can be formed in a hydroforming machine in approximately 10 min. With the addition of residual heat in the bladder and some process optimization it may be possible to reduce the actual cycle time 30% further

A large hydroforming tray bed may be able to form 4–6 parts in one cycle. A 10-min cycle running 4 parts produces a 2.5-min average part cycle time. A 250 days' work year, running a 7-h shift would produce 42,000 parts per year. The envisioned ability to form and cure metal composite laminated parts in one single hydroforming process step has yet to be

the different convective mediums display different curing rates.

to 7 min. Physical experiments are needed for validation.

**Figure 23.** Effect of the aluminum tool on the overall curing process.

**Figure 22.** Bladder temperature history.

**Figure 23.** Effect of the aluminum tool on the overall curing process.
