F2020 - Bottom Panel Structural Evaluation
- Tommy Tran
For MSXIV, there was large difficulty manufacturing a structural bottom panel due to its size and complexity. Structural testing was needed to be carried out to evaluate the structural properties of the initial layers of the bottom panel that has been manufactured so far.
Structural testing of the bottom panel consisted of a 3-point flexural test that follows the standards for ASTM D790 - the determination of flexural properties of unreinforced and reinforced plastics and electrical insulating materials.
Specimen Preparation
Source: https://www.instron.us/testing-solutions/by-test-type/flexure/the-definitive-guide-to-astm-d790
ASTM D790 Standard: 3.2 mm x 12.7 mm x 125 mm
0.125” x 0.5” x 5.0”
Dimensions of ASTM D790 specimens depend on the thickness of the material, which the start defines as being the depth of the specimen
Sheet materials with a thickness between 3.2 and 1.6 mm will have a width of 12.7 mm and a support span defined as specimen thickness X 16
Sheet materials less than 1.6 mm in thickness will be 50.8 mm X 12.7 mm with a 25.4 mm support span
Carrying Out the Test
Source: https://www.instron.us/testing-solutions/by-test-type/flexure/the-definitive-guide-to-astm-d790
Procedure A:
Preferred method
Employs strain rate of 0.01 mm/mm/min
Procedure B:
Employs a strain rate of 0.10 mm/mm/min
Intended for materials that may not break at 5% strain if tested at the lower rate
Data Processing
Source: https://en.wikipedia.org/wiki/Three-point_flexural_test#Standards
Results
Table #1: List of variables recorded for experiment
Variable | Quantity | Note |
|---|---|---|
L = Support Span (mm) | 31.6 | Approximate measurement |
b = Width of test beam (mm) | Varied by Specimen | Averaged measurement |
d = depth of beam (mm) | Varied by Specimen | Averaged measurement |
Load rate (mm/min) | 1 mm/min | Greater than standard, but was used for sake of time and practicality |
Maximum deflection (mm) | 3 mm | Greater than standard, but allowed to show the material’s properties consistently up to failure |
Table #2: Dimensions of test specimens
Specimen | L = Support Span (mm) | b = Width of test beam (mm) | d = depth of beam (mm) | m (N/mm) |
|---|---|---|---|---|
1 | 31.6 | 16.51, 15.92, 15.53 avg = 15.987 | 1.15, 1.33, 1.09 avg = 1.19 | 120 |
2 | 31.6 | 14.63, 15.61, 14.39 avg = 14.877 | 1.38, 1.59, 1.42 avg = 1.463 | 94 |
3 | 31.6 | 15.24, 15.35, 15.10 avg = 15.23 | 0.98, 0.96, 0.93 avg = 0.957 | 35.7 |
4 | 31.6 | 13.70, 14.42, 14.62 avg = 14.247 | 0.98, 0.92, 0.92 avg = 0.94 | 10.4 |
Graphs of Specimens
General Comment:
It shows that the specimens peaked and then its performance began to deteriorate or plateau. When it peaks, the fibres break and loses its structural properties.
Figure #1: Load and Deflection of Specimen 1. Max Force is about 72N at 0.5mm deflection
Figure #2: Load and Deflection of Specimen 2. Max force is about 87N at 0.9 mm deflection
Figure #3: Load and Deflection of Specimen 3. Max force is 50N at 1.4mm deflection
Figure #4: Load and Deflection of Specimen 4. Max force is 13N at 1.25mm deflection
Numerical Results
Table #3: Structural Properties of Specimens at their peak performance during testing
Specimen | Flexural Stress (MPa) | Flexural Strain (mm/mm) | Flexural Modulus (MPa) |
|---|---|---|---|
1 | 150.7474382 | 0.012870534 | 35137.81 |
2 | 129.5071002 | 0.007911593 | 15917.72 |
3 | 169.9122016 | 0.008050393 | 21097.63 |
4 | 48.94885783 | 0.007060167 | 6933.102 |
General Comments:
There can be variation in performance based on where the sample was collected on the bottom panel. Not all specimens were the same initial thickness or stiffness.