Calculating strength of UD laminate from a Quasi-isotropic laminate

[Jasim90]

Hi all

As I having trouble doing the tensile tests for a UD carbon/epoxy laminate, I decided to do the tests for a quasi-isotropic layup in order to avoid fibre-bridging and grip failure in the case of UD samples.

Is there a good approximation technique that will enable me to back calculate the strength of a UD from a quasi-isotropic layup?

Kind Regards

 

[SWComposites]

Calculate the failure strain in the quasi laminate (P/AE). Assume that the failure strain of the UD is the same as for the quasi laminate - it is a reasonable assumption for tension, less so for compression.

 

[Jasim90]

Thanks a lot for that!

I just realised that I made a mistake during the layup. The panel is supposed to have a balanced symmetric layup [45/0/-45/90]2s. But I made it [45/0/-45/90]4. Because of this my test coupons have a slight curvature, not perfectly straight.

How much will this influence my strength results ?

 

[SWComposites]

In tension, probably less than 10% effect, but that's just a rough guess without running any numbers.