ILSS v Tensile strength

[TheBigM]

Some time ago I read a paper which discussed the relationship between ILSS and tensile strength in that to a certain extent ILSS goes down as tensile strength goes up and vice versa. Can't remember the exact content now and so I'd like to re-read it but I can't find it. Does anyone know of a publication or item which mentions this relationship?

M

 

[ESPcomposites]

Are you defining ILSS as interlaminar shear strength or interlaminar shear stress?

Under tensile loading of an unnotched laminate, free edge delamination can occur before fiber fracture. If so, then a reduction in interlaminar shear stress (or increase in interlaminar shear strength) will increase tensile strength of the laminate. So if the failure is already fiber dominated, then ILSS has no effect. As far as papers go, I can have a look. I have seen dozens that discuss this though.

For notched laminates (the far more common case), the effect is less obvious. Localized delamination can improve strength by softening stress concentrations. This tends to offset the disadvantages of delamination.

In general, we use well dispersed layups to minimize interlaminar stresses. By abiding by standard design practice, the effects of ILSS are mitigated (and we usually ignore them).

There is a fracture mechanics based approach to predict the onset of free edge delamination, but that is only relevant to unnotched laminates.

Brian

http://www.espcomposites.com

 

[SWComposites]

For some carbon fiber polymer composite materials the uni tension strength is inversely related to the interlaminar shear strength. The higher the fiber/matrix interface bonding the higher ILSS but lower tension strength. This is really only a significant effect for very high modulus (low strain) carbon fibers.

Sorry, but I don't recall particular papers off the top of my head; try a search a scholar.google.com

 

[TheBigM]

Thanks for the comments guys.