If I follow what you are saying correctly, you are doing a three point bend. You have two support rods and are pressing the sample bar down at the middle?

You might have to substitute a different method, such as tensile strength in ASTM D638. "Flexural strength" might not be meaningful if the material has high enough elongation at failure.

3 point bending won't help in this case. do a tensile test, ideal under Hencky-conditions, i.e. with exponentially increasing strain rate.

Dear Jasvinder,

Like other RG colleagues, I assume that you are referring in your question at the determination of flexural strength of polycaprolactone (PCL).

You will find in the literature some information about the flexural modulus, the force needed to obtain a constant/established deformation, but not about the break of specimens by flexion (because of its high flexibility and low modulus).

Please take a look here: https://www.astm.org/Standards/D790.htm

(NB: Materials that do not rupture by the maximum strain allowed under this test method may be more suited to a 4-point bend test.)

If you will test composites and rigid blends based on PCL using thicker specimens, I assume that you will arrive to obtain all information.

On the other hand, if you are considering in your question the tensile tests to determine the mechanical strength of PCL,only by fixing well the specimens and using adequate speed of testing, you will arrive to obtain all information (e.g., tensile strength at yield and break, Young’s modulus),.

Good luck and best regards,

Marius

PS: For eventual help

https://www.researchgate.net/publication/270509196_Bulk_Mechanical_Porperties_of_Thermoplastic_PCL

https://accedacris.ulpgc.es/bitstream/10553/42002/2/3d%20printed%20pcl-mcc%20scaffolds.pdf

https://www.researchgate.net/figure/Flexural-modulus-of-PLA-PCL-clay-nanocomposites_fig18_264391644

I agree to most of your points, Marius Murariu .

But I expect that for polycaprolactone only a tensile test will lead to rupture. We recently submitted a paper on polycaprolactone and had some tensile testing of different specimen in it. None of the samples broke at less than 800% engineering strain and that cannot be properly achieved by a bending test.

Besides that I am not a friends of bending experiments at all, unless you want to stay linear viscoelastic or you have very brittle materials (clamping for glasses or ceramics is difficult). The simple reason is that in a bending test, you have a mixed (elongation/compression) deformation, which means as soon as you have a heterogeneous sample or a sample with a Poisson ratio different from 0.5, you will run into difficulties in evaluating the data properly.