SAMPE Journal - May/June 2011 - 39

Figure 4. Compression molding process and demolding. Manufacturing: Compression Molding Process Compression molding (CM) is a high-volume, high-pressure method suitable for molding complex parts. There are two main types of CM process, which are sheet molding compound (SMC) and wet lay-up compression molding. MX4926 MC is manufactured by SMC process using 12 mm by 12 mm squares of SMC. These squares are placed into mold cavity, heated, and pressed for a certain period of time Molding Compound Preparation The first step of the manufacturing process was the preparation of prepreg laminates. Carbon fabric and resin were taken in proportion to achieve desired fiber volume fraction and density of the material. The desired fiber volume fraction was 50/50 by volume. Wetting was achieved using hand layup process. The prepreg was visually inspected for dry spots. Then, the prepreg was weighed again and placed into preheated oven to 163º C for 30 minutes. Further prepreg was weighed again in order to confirm volatile – weight loss of prepreg. After the prepreg is cooled, it is manually cut to 12 mm by 12 mm squares using cutting board (Figure 3). Compression Molding Wabash automatic hydraulic compression press (30 ton capacity) was used in this study to manufacture test panels. A two part compression mold was used. . The mold cavity was 120 x 120 x 12.7 mm. It was made of high carbon steel and was used with an appropriate mold release agent. The mold and the press’ platens were preheated to 163° C prior to use. Chopped prepregs (sheet molding compound) were placed in the mold cavity and placed in the press (Figure 4). The press was then closed with 30 T force, which provided about 2600 psi (about 18 MPa), for 1 hour at 163° C. The mold was removed from the press; and the panel was removed from the mold cavity. After the panel was cooled in the air, it was weighed in air and in water to calculate specific gravity of materials. The target specific gravity was 1.46 – the same as that of MX-4926. Density is one of the key properties of ablative materials. Radiant Panel Testing The QH radiant heat panel manufactured by Solar Products, Inc. Pompton Lakes, NJ is used to simulate fire environment for this study. The panel is 25.4- x 25.4-cm (10- by 10-in.) with fused silica (opaque quartz) face. The properties of quartz make for a very efficient radiator of infrared energy. The back of each fused quartz face is precision machined to hold the resistance coil. With the coils resting in the grooves, the coils are surrounded by three walls of quartz, thereby maximizing the energy output of the heater. Aluminized steel casings and welded stainless steel terminations are standard throughout. The QH model has a maximum watt density of 60 wsi (93 kW/m2). The radiant heat panel is shown in Figure 5. This setup was placed in a fume hood to protect users from potential exposure to hazardous fumes. More detailed description of the experimental setup and heat flux measurements can be found in reference10.

Figure 5. Radian panel during testing.
SAMPE Journal, Volume 47, No. 3, May/June 2011

Figure 6. Data collection system – IR pyrometer (front), 4 channel data-logger thermometer (middle).
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SAMPE Journal - May/June 2011

Table of Contents for the Digital Edition of SAMPE Journal - May/June 2011