Tensile strength test of printed specimens

[jumpmobile 0]

Hey there

some months ago i posted a CAD-modell of some test specimens for tensile strength tests on Thingiverse. Today "Vestro", posted a reply with some measurements he made.

As you can see the orientation of the print is very improtant.

(plz. correct me if i am posting anything wrong)

The minimum force you need to crack a printed part in x- or y- direction is twice as high as the force required to tear the layers in z direction apart. Also the elongation before breaking is almost three times higher in x,y-direction than in z-direction.

It has been known before that z-layers are the weak points of any printed objects, but i find it interesting to see that the factor is about 0.5 of original (?) tensile strength.

I asked Vestro to post what filament he used. If the seller provides a datasheet (and we assume that the vendor hat its product tested instead of just guessing its properties) we could determine how much strength loss there has been from original filament to the printed form.

Thanks to Vestro for making this...

 

[jonask 0]

Hello, today i also did some strength tests in my university and i want to share the results with you.

I tested Black abs http://www.conrad.de/ce/de/product/555893/3D-Drucker-Filament-Velleman-ABS3B1-ABS-Kunststoff-3-mm-Schwarz-1-kg/SHOP_AREA_857889?

I printed the 1BA.stl from here http://www.thingiverse.com/thing:190386/#files

all parts were printed flat on the build plate.

I tested 4 samples.

Print parameters:

All speeds: 50mm/s

100 %infill

0.8shell

1 sample: 260°C 100% infill

2 sample: 250°C 100% infill

3 sample: 240°C 100% infill

4 sample: 260°C 110% infill

Diagrams:

(notice: The first Sample should be ignored, it was a normal (non printed) plastic probe, so my first sample starts with number 2)

 

So what you can see is that with lower Temp the strength goes down. No big suprise.

But the last Sample with 260°C and 110% got a very good improvement on the breaking elongation.

 

Under the microscope you can see that the infill did not really melted together. While the two outer lines were much stronger. So it looks like i need to go up with the flow rate.

 

Its funny because with the eyes only, it looks almost over extruded, but under the microscope you could see that the lines are not always touching each other.

 

Also under the microscope the outer lines didn't look different at 100% flow or 110% flow. Witch means going up with the flow rate should not affect print quality that much.

 

Here are the pictures of the broken surface. The whiter the surface is, the more deformation it gets before it did break.

So you can see all three 100% flow rate samples have very bad sticking on the infill, but quite good sticking on the outerlines. Even the sample with 110% flow rate still got not a perfect infill.

 

I will try to do some other tests with lower speed, more flow, and thinner nozzle size in cura soon.