**4.1. Analysis type and geometry**

*2.1.2. Quickstep composites*

30 Characterizations of Some Composite Materials

*2.1.3. Thermo-hydroforming*

or intelligent components.

**2.3. Technical objective**

prepreg materials or resin injection molding [12, 13].

**2.2. GLARE® laminate with S-2 glass fiber by AGY**

comfortably to 425°F (218°C) and 10,000 psi/700 Bar.

been recognized as one of the top aerospace materials for the future.

Quickstep is an Australian-listed company. The Quickstep process forms composite parts using 4 psi (low pressure) on a rigid tool suspended between two elastomeric membranes back filled with glycol fluid. Their large format out of autoclave forming and curing process works well for large parts. Aerospace parts such as wing skins can be molded using either

In this chapter, an "Out of Autoclave (OOA) HydroElastic Hydroforming" method is proposed to utilize pressurized water as a forming fluid behind an elastomeric membrane. The shell tool is water heated and backed by a high strength reusable fiber/epoxy composite [14–24]. In addition to the forming chamber shown, an outer sleeve chamber is used to contain extremely high pressures [25, 26]. Because of this high-pressure capability, the system can simultaneously form laminate stacks of both metal and composite material strata using the OOA hydroforming approach. This opens new potential possibilities for metal [27–32] and fiber reinforced composite flat panel [33–35] as well as contoured part designs [36, 37].

One of the most exciting materials under evaluation for primary and secondary aircraft components is GLARE laminate. Glass Laminate Aluminum Reinforced Epoxy (GLARE) is a sandwich material constructed from alternating layers of aluminum and S-2 Glass® fiber with bond film. The material, developed at Delft University of Technology in the Netherlands, has

It is believed that thermo-hydroforming has the potential to form GLARE multi-sheet material stacks. This would create a 3D conformal forming process that allows full design engineering of complex 3D shaped parts as needed. The parts are formed in a tool die that allows the part to be configured exactly as needed for the specified function. In addition, thermohydroforming forming, will enable subtle surface inflections to be made in parts for things such as flush access doors, flush rivets and flanges as well as embedded cast–forged, electrical

This project seeks to gain a foundational understanding of the proposed thermo-hydroforming machine's performance by conducting FEA simulations [38–40]. This simulation studies a multiply coupon of carbon fiber prepreg being formed by a vulcanized silicone elastomeric bladder. The bladder is heated and pressed into the composite coupon by water heated to 285°F under 300 psi of pressure. The tool is pre heated to the temperature of 285°F as well. As a result, the composite coupon is heated from above and below. This process should be used

We understand from work by Globe manufacturing, Quickstep Composites and other prior art that both air and fluid heat behind a membrane can be used to react and cure prepreg materials. It is also known that pure water has one of the best thermal conductors. Water The first load step consists of a linear static analysis where only the pressure load is applied. This allows for the composites to be in contact with the tool. Following this, a transient coupled thermal displacement step is run to obtain the temperature distribution and heat flux through time. Total time used was 200 s.

**Figure 2.** Thermal expansion of select materials.

The geometry consists of an expandable silicon rubber bladder, which contains a convective medium inside. This convective medium is not modeled, however, the effects of convection on the general temperature distribution are important and therefore, simulated. Two different bladder thicknesses were evaluated: 6 mm and 12 mm. The bladder sits on top of a Torayca 300 carbon/epoxy prepreg laminate consisting of the following stacking order: (0, −45, 90, 45)2

Out of Autoclave Metal and FRP Composites Thermo-Hydroforming

http://dx.doi.org/10.5772/intechopen.81600

a) The rubber bladder at room temperature is pressurized with hot fluid (285°F). The bladder

b) The Rubber bladder expands downward due to the exerted pressure of 300 psi and pushes

c) The composite laminate which has a cold OTF (Out of Freezer) temperature of 65°F is heated by the tool and rubber bladder by means of thermal conduction until thermal equi-

The following mechanical and thermal properties (**Tables 1**–**3**) of the respective component's

Shown in **Figure 6**, the bladder is fixed from the top, to allow the bottom to expand downward, pushing the composites towards the tool. The tool is also fixed so the compressive load

Shown in **Figure 7**, a uniform pressure of 300 psi was applied to the bottom inner surface, to simulate the bladder expansion which pushes the composite towards the tool. Initial tempera-

**Material Elastic modulus (Mpa) Poisson ratio Density (Ton/mm<sup>3</sup>**

Composite Laminate 135,000 0.3 1.76E-09 Steel 210,000 0.3 7.89E-09 Silicon Rubber 50 0.48 1.70E-09

heats up by convection until it reaches thermal equilibrium with the hot fluid.

the composite laminate onto the aluminum tool which is also heated to 285°F.

material were assigned to the different parts to proceed with the FEA simulations.

The laminate sits on top of a concave aluminum tool (**Figures 4** and **5**).

**4.2. Load steps**

librium is achieved.

**4.4. Boundary conditions**

is applied to the composites.

**4.5. Loading conditions**

**4.3. Thermomechanical properties input**

tures assigned to the parts were shown in figure.

**Table 1.** Mechanical properties of assigned materials.

.

33

**)**

**Figure 3.** H2 O pressure vs. boiling temperature.

**Figure 4.** General dimensions of the model.

**Figure 5.** Assigned materials for each component.

The geometry consists of an expandable silicon rubber bladder, which contains a convective medium inside. This convective medium is not modeled, however, the effects of convection on the general temperature distribution are important and therefore, simulated. Two different bladder thicknesses were evaluated: 6 mm and 12 mm. The bladder sits on top of a Torayca 300 carbon/epoxy prepreg laminate consisting of the following stacking order: (0, −45, 90, 45)2 . The laminate sits on top of a concave aluminum tool (**Figures 4** and **5**).

## **4.2. Load steps**


#### **4.3. Thermomechanical properties input**

The following mechanical and thermal properties (**Tables 1**–**3**) of the respective component's material were assigned to the different parts to proceed with the FEA simulations.

#### **4.4. Boundary conditions**

Shown in **Figure 6**, the bladder is fixed from the top, to allow the bottom to expand downward, pushing the composites towards the tool. The tool is also fixed so the compressive load is applied to the composites.

#### **4.5. Loading conditions**

**Figure 5.** Assigned materials for each component.

**Figure 4.** General dimensions of the model.

**Figure 3.** H2

O pressure vs. boiling temperature.

32 Characterizations of Some Composite Materials

Shown in **Figure 7**, a uniform pressure of 300 psi was applied to the bottom inner surface, to simulate the bladder expansion which pushes the composite towards the tool. Initial temperatures assigned to the parts were shown in figure.


**Table 1.** Mechanical properties of assigned materials.


**4.6. FEA results**

*4.6.1. Load step 1: bladder heating*

due to convection (**Figures 8**–**11**).

**Figure 8.** Nodal temperature results at t = 0 s (initial state).

**Figure 9.** Nodal temperature results at t = 8.38 s.

**Figure 10.** Nodal temperature results at t = 70 s.

**Figure 11.** Nodal temperature results at t = 120 s (bladder completely heated up).

During this first load step, thermal conduction between the bladder and the composite laminate is ignored, this allows for the display of the thermal contour of the bladder as it heats up

Out of Autoclave Metal and FRP Composites Thermo-Hydroforming

http://dx.doi.org/10.5772/intechopen.81600

35

**Table 2.** Thermal properties of assigned materials.


**Table 3.** Convection coefficients for different liquids.

**Figure 6.** Boundary conditions applied to the model.

**Figure 7.** Initial temperatures for each part.

#### **4.6. FEA results**

**Material Convection coefficient (mW/mm<sup>2</sup>**

**Material Heat conductivity specific heat**

Composite Laminate 10.46, 7.2, 9 795,000,000 Steel 43 466,000,000 Silicon Rubber 1.375 1,180,000,000

**Table 3.** Convection coefficients for different liquids.

**Figure 6.** Boundary conditions applied to the model.

**Figure 7.** Initial temperatures for each part.

**Table 2.** Thermal properties of assigned materials.

34 Characterizations of Some Composite Materials

Free air 0.0015 1X Free water 0.06 40X Moving water 5.15 3433X

 **K) Efficiency**

**Coefficient (mJ/mm K) (mJ/Ton K)**

#### *4.6.1. Load step 1: bladder heating*

During this first load step, thermal conduction between the bladder and the composite laminate is ignored, this allows for the display of the thermal contour of the bladder as it heats up due to convection (**Figures 8**–**11**).

**Figure 8.** Nodal temperature results at t = 0 s (initial state).

**Figure 9.** Nodal temperature results at t = 8.38 s.

**Figure 10.** Nodal temperature results at t = 70 s.

**Figure 11.** Nodal temperature results at t = 120 s (bladder completely heated up).

#### *4.6.2. Load step 2: bladder expansion*

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