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## Main Question or Discussion Point

Hi Guys

I am trying to figure out what stresses in different planes mean physically for composite laminates.

Say S stands for stress then

SXX SYY SZZ would be longitudinal/axial stresses in respective Axes. (If we take the laminates to be in XY plane, failure stress SZZ would be equal to laminate strength/delamination right in tension?)

SXY would be in plane shear stress. For Unidirectional, it could also give relationship for shear failure between fibres and matrix (debonding of fibres)?

For woven type composites, what would they mean? (Something complex I suppose? A laminate highly unlikely to fail in SXY if woven ? )

SXZ and SYZ would be related to delamination of composite in shear ?

Please correct me in my above statements if I am wrong.

Also, why is SZZ so important for FEA solvers (At least ANSYS). Would a very simplified loading case such as bending and/or longitudinal loading, SZZ would be redundant? How does one estimate value for SZZ analytically (no testing facility available for measuring stiffness/strength in Z direction)

Sorry if I sound confused.

Looking forward to your replies

I am trying to figure out what stresses in different planes mean physically for composite laminates.

Say S stands for stress then

SXX SYY SZZ would be longitudinal/axial stresses in respective Axes. (If we take the laminates to be in XY plane, failure stress SZZ would be equal to laminate strength/delamination right in tension?)

SXY would be in plane shear stress. For Unidirectional, it could also give relationship for shear failure between fibres and matrix (debonding of fibres)?

For woven type composites, what would they mean? (Something complex I suppose? A laminate highly unlikely to fail in SXY if woven ? )

SXZ and SYZ would be related to delamination of composite in shear ?

Please correct me in my above statements if I am wrong.

Also, why is SZZ so important for FEA solvers (At least ANSYS). Would a very simplified loading case such as bending and/or longitudinal loading, SZZ would be redundant? How does one estimate value for SZZ analytically (no testing facility available for measuring stiffness/strength in Z direction)

Sorry if I sound confused.

Looking forward to your replies