I've seen a research article that tested a polymer sandwich structure in 3-point bending according to ASTM C393. Their testing parameters included a 100 mm span length, a 2.0 mm/min loading rate, and specimen dimensions of 150 mm length, 18 mm thickness, and 32 mm width. Can I use these same dimensions for my own samples?. Or is there any rule to find the specimen dimensions?
The dimensions of the specimen indicated are ok. Please see the peak load for failure/flexure takes place within the capacity of the UTM.
No, you shouldn't use those exact dimensions from the article. They actually don't comply with ASTM C393 requirements.
The article used:
- 100 mm span with 18 mm thickness (S/t ratio = 5.56)
- This violates the ASTM minimum S/t ratio of 20
For proper ASTM C393 testing, you should:
If lab constraints make this difficult, consider reducing your sample thickness to maintain proper ratios. For example, with 6 mm thickness, you'd need only 120 mm span while maintaining ASTM compliance.
Hope this helps your research!
You can use the same specimen dimensions for your samples, but you should ensure they comply with ASTM C393 guidelines. The standard recommends that the span length should be at least 10 times the total thickness of the sandwich specimen. In your case, with an 18 mm thickness, the span length should be at least 180 mm, whereas your chosen span is only 100 mm, which may be too short for accurate results. The width of 32 mm is appropriate, as ASTM suggests a minimum of three times the core thickness. The loading rate of 2.0 mm/min is within the acceptable range for quasi-static flexural tests. If you aim to follow the standard strictly, increasing the span length is recommended for more reliable bending test results.
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