For UD CFRP laminates, what's the relationship between matrix plasticity and modulus decrease (damage related properties) after fatigue tests?

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Vijay Verma

when fatigue loading is applied on the specimen the the main load is sustained by the fibers but the matrix also plays an important role in fatigue life as during fatigue loading the displacement of the fibers and the matrix has to be same but in normal cases the displacement of matrix is more then reinforcement thus the relative motion between both with will start matrix / fiber delamination dur to shear acting between both dur to relative motion.......

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Yan Ma

Dear Vijay Verma,

Thanks very much for answering this question.

I am doing the off-axis (45 degree) fatigue of UD CFRP laminates including CF/PA6 and CF/Epoxy laminates. I found the modulus of CF/PA6 decrease a lot than CF/Epoxy laminates. On the other hand, the fatigue limit of CF/Epoxy laminates is higher than CF/PA6. I think the stiffness degradation is caused by the damage of interface by the shearing effect. On the other hand, the elongation of CFRP increased owing the more flexible/ductile properties of matrix after fatigue tests. Actually, i am not sure the fatigue mechanism between off-axis UD CF/PA6 and CF/Epoxy lamiantes. Could you please give me more suggestions?

Best wishes,