Overview:
To match conditions similar to those expected from the high speed flight, a propane blowtorch will be used to heat small samples of different materials with different ablative coatings (see test matrix below) while a thermocouple will monitor the surface temperature of the materials. After the test we will also be measuring the samples to estimate the ablationThe mass and thickness of the samples will be measured before and after the test to determine the effectiveness of the ablative coating used. A test stand has been built to hold the propane blowtorch at a specific distance from the samples and a remote trigger mechanism allows operators to be a safe distance from the blowtorch and sample.(which can be adjusted as necessary).
The tests will be performed in a secure environment (blast chamber) and the operators will wear respirators during the tests. This document from Apogee Components was used as inspiration for this test procedure. Apogee Newsletter
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Below is the matrix for samples used in this thermal test. All samples measured ~2 ~2" x 2" (with thickness depending on the sample), and there are three samples for each combination (for three trials).
| 1/4" phenolic sheet | |||||
| 5-Layer Fiberglass | 10-Layer Fiberglass | ||||
|---|---|---|---|---|---|
| Control (West Systems epoxy) | 1/4" phenolic sheet | ||||
| West Systems + Phenolic microballoons | |||||
| West Systems + Cork microballoons | |||||
| West Systems + High temperature paint | |||||
| West Systems + Cotronics 4700 | |||||
Sample Preparation:
- Used West Systems epoxy to make 4 of 8" x 8" sheets of fiberglass (2 x 5 layers, 2 x 10 layers)
- Sanded with a Dremel, then with 400-grit sandpaper. Make sure to sand the shiny side as well
- Mark and cut into 1.5" x 1.5" squares.
- Recorded dry mass of each sample
- Took three measurements of thickness on three different sides, and calculated/recorded average thickness
- Wearing respirators, mixed 50 g. West Systems resin + 9 g West Systems hardener
- Mixed in phenolic microballoons until a consistency slightly thinner than peanut butter (like melted ice cream) was reached
- Applied phenolic mixture using popsicle sticks and left to cure for 36 hours
- Recorded average thickness of samples with phenolic coating
- Sanded with 400-grit sandpaper then recorded mass (and wiped with acetone)
- Applied high-temp paint to fiberglass samples (series 6,7) and fiberglass + phenolic samples (series 8,9)
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