Lamina Properties vs Laminate Properties

[midsidenode]

How does one find the lamina properties via a test. In other words, if a laminate is tensile tested IAW ASTM 3039 to get an ultimate tensile strength, can a lamina ultimate tensile strength be derived from from that test also.
thanks,
msn

 

[tmvo]

Hi midsidenode,
Yes, mechanical properties of lamina could be derived from the testing cured laminate. However, it is depending on the stack sequence of your laminate. Generally, to derive mechanical properties for lamina, the laminate usually layup in unidirectional then test in the desired direction to obtain the proper properties.

Regards,

 

[midsidenode]

Thanks tmvo. So if I understand you correctly, If I follow the requirements of (let's say) astm 3039 to perform a tensile test of 8 plies all laid up in the zero direction, the ultimate stress in the laminate equals the ultimate stress in to lamina - right or not?
Thanks
Msn

 

[RPstress]

That is indeed the case. The only non-all-the-same-direction coupon test for lamina properties is the ±45° tension test for 12-direction (shear) properties. It is a bit questionable as to how good that test is for strength, though the G derived for small test strains shold be reasonable. The test spec-recommended specimen thicknesses should mean that the lamina properties derived should be usable for most purposes (often some sort of classical laminate theory use, perhaps for FE analysis).

 

[tmvo]

That is right. However, as mentioned by RPstress, there are certain requirements for every specific test. You should comply with ASTM standards before testing to obtain the best result. If I am not wrong, you need to meet geometry and tabbing requirements. In addition, the fiber alignments are very sensitive in tensile test.