To match conditions similar to those expected from the high speed flight, a blowtorch will be used to heat small samples while a thermocouple will monitor the surface temperature of the materials. After the test we will also be measuring the samples to estimate the ablation. A 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.
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
Materials Used:
- Fiberglass
- West Systems 105 epoxy (resin + hardener)
- Phenolic microballoons
- POR 15 High-temp Heat Resistant Paint
- 400-grit sandpaper
- Small popsicle sticks
- Mixing boat for epoxy
- Dremel
- Worthington propane blowtorch (14.1oz)
- Arduino Uno
Thermocouple Amplifier MAX31855 breakout board (MAX6675 upgrade): https://www.adafruit.com/product/269
K-type thermocouple: https://www.adafruit.com/product/270
Jumper wires
- Breadboard
- Test stand
- Calipers
- Mini scale
- Gloves, respirators
Below is the matrix for samples used in this thermal test. All samples measured ~2 x 2", and there are three samples for each combination (for three trials).
| 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)
Below is the test matrix for the parameters measured during this test. (MAKE SUMMARY, ATTACH EXCEL FILE).
| Fiberglass- CONTROL | Fiberglass + Phenolic Microballoons | Fiberglass + High-temp | Fiberglass + Microballoons + Paint | Phenolic | |||||||||||||||||||||||
| 5-Layer | 10-Layer | 5-Layer | 10-Layer | 5-Layer | 10-Layer | 5-Layer | 10-Layer | ||||||||||||||||||||
| 2-1' | 2-2' | 2-3' | 3-1' | 3-2' | 3-3' | 4-1' | 4-2' | 4-3' | 5-1' | 5-2' | 5-3' | 6-1' | 6-2' | 6-3' | 7-1' | 7-2' | 7-3' | 8-1' | 8-2' | 8-3' | 9-1' | 9-2' | 9-3' | 1-1' | 1-2' | 1-3' | |
| Initial dry mass (no hole) - oz | 0.135 | 0.130 | 0.150 | 0.290 | 0.295 | 0.280 | 0.140 | 0.150oz | 0.160 | 0.305 | 0.300 | 0.305 | 0.150 | 0.130 | 0.135 | 0.295 | 0.280 | 0.305 | 0.140 | 0.140 | 0.140 | 0.270 | 0.270 | 0.285 | 0.785 | 0.780 | 0.780 |
| Initial dry average thickness - mm | 1.016667 | 1.01 | 1.043333 | 2.053333 | 1.996667 | 1.95 | 0.993333 | 0.963333 | 1.083333 | 2.126667 | 2.13 | 2.046667 | 1.093333 | 0.936667 | 0.91 | 1.936667 | 1.84 | 1.886667 | 0.846667 | 0.84 | 0.803333 | 1.75 | 1.753333 | 1.75 | 6.2 | 6.153333 | 6.13 |
| Thickness 1 | 1.03 | 0.98 | 1.03 | 2.08 | 2.02 | 2 | 1 | 1.01 | 1.06 | 2.26 | 2.05 | 2.01 | 1.07 | 0.92 | 0.88 | 1.92 | 1.83 | 1.85 | 0.79 | 0.84 | 0.84 | 1.8 | 1.8 | 1.78 | 6.18 | 6.16 | 6.14 |
| Thickness 2 | 0.97 | 1 | 1.06 | 2.02 | 2.02 | 1.94 | 1 | 0.94 | 1.07 | 2.08 | 2.16 | 2.06 | 1.16 | 0.92 | 0.91 | 1.94 | 1.85 | 1.89 | 0.86 | 0.85 | 0.81 | 1.75 | 1.74 | 1.74 | 6.21 | 6.15 | 6.12 |
| Thickness 3 | 1.05 | 1.05 | 1.04 | 2.06 | 1.95 | 1.91 | 0.98 | 0.94 | 1.12 | 2.04 | 2.18 | 2.07 | 1.05 | 0.97 | 0.94 | 1.95 | 1.84 | 1.92 | 0.89 | 0.83 | 0.76 | 1.7 | 1.72 | 1.73 | 6.21 | 6.15 | 6.13 |
| Initial wet mass (no hole) - oz | |||||||||||||||||||||||||||
Test Stand
<insert pics>
Setting up thermocouples
Samples
Test Procedure:
Testing in blast chamber
Heat for 12 seconds
Improvements for Next Tests:
- When preparing the samples (fiberglass layup), use a flatter surface so that the average thickness is more consistent
- If testing high-temp paint, use more than one coat so that there is enough paint to show results
- Find some way of remote-triggering the blow torch for added safety
- Use a more accurate scale so that initial and final mass is more accurate
- When measuring thickness (for average thickness calculation), be consistent when choosing points to measure on the sample, and take more than three measurements for a more accurate estimate
