Calculations for N-Oriented Carbon Fibers in a PEEK Matrix

2 Calculations for N-Oriented Carbon Fibers in a PEEK Matrix 

To simulate debonding phenomena that can occur during the scratch test described in Section 2, at first contact calculation must be carried out. At a normal load Ff) = 1 N, the measured coefficient of friction between the diamond indentor and the CF/PEEK specimen for N-fiber orientation was /x = 0.1. 

Both Ef and y higher than the real values, due to the limitation of the slope angle. The solutions for more radical degression of the stress-strain curves require further studies and probably a new solution technique. 

The debonding conditions in the problems studied were evaluated as in Section 5.1.2. At the maximum load, a total of 192 elements reached the final debonding state (i.e., less than 0.7% of all interface elements). In the present case, final tension type debonding was not obtained. The reason for this is the rather low value of the coefficient of friction (as measured for the diamond indentor, i.e., 0.1). On the other hand, in previous wear studies with a steel disc and a normally oriented CF/PEEK material, the coefficient of friction was clearly higher (jLtjteei=0 45). ° In this case, debonding effects could probably occur much easier. 

When modeling the fiber/matrix micro-structure, in order to study wear and failure mechanisms in real fiber-reinforced composites, an FE macro/micro contact model (introducing the displacement coupling technique) is much more suitable than using an equivalent macro-model. As a result, the calculated contact, stress, and strain results are significantly closer to the real conditions. 

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