Help with calculating Max load

I just checked your calculations and they seem to be fine given that the area is fixed. But we need to know if the area changes during the tensile test. I believe the stress in the normal direction will cause lateral strain to take place and the actual area may be reduced. Has this been factored into the calculations for area?

We use the original area so we use the engineering stress values

I thought I was right but maybe my predicted values are wrong.

Thanks for the response

I agree with this post, the samples likely necked down during testing, and if you recalculated using actual (reduction in area experienced) they are likely to be closer in agreement to your expected values.

milo

Upon completing your calculations; can you test the "part" in a stress tester, like Instron or Chatillon?

Ronald the figures i have given are from the tensile test

I apologize, I read the post too fast and over-looked it...

No problem Ronald

I had a look at the models you mentioned. The one considers the 2 materials parallel to each other and leads to the sum of σ and the other looks at the sum of ε.

In fact -I presume- you have alternated layers at 45° to the direction you apply the load. In such a case the shear strains give the limit.

My suggestion is to use other equations in fact other models of the 2 component-material) as well which could be better for the loading case you are confronted with.

Please do not forget that you deal with a stuff which is build up by 2 components with different E-modules and that you measure the global force and the global strain but failure is done by a local destruction and weak point of the internal structure.

Thanks Nickname.

I am coming to the conclusion that the material we used for the samples was well past its use date.

Also the Woven materials predicted values should include an orientation factor that should take into account the orientation of the fibres. For a 45/45 laminate this is 0.25 and 0/90 is 0.5 this brings the predicted values well in line with the actual values.

If anyone is interested I will post my report whaen I am done. I wouldnt mind some sort of critic on it.

Matt