The influence of fiber orientation and geometry-induced strain concentration on the fatigue life of short carbon fibers reinforced polyamide-6

Static and fatigue mechanical properties of a polyamide-6 reinforced with a 20% weight fraction of short carbon fibers (PA6-20CF) material were investigated by means of static and fatigue tensile tests on both unnotched and notched specimens. SEM pictures were also taken on the fracture surface of specimens tested under static, low cycle failure (LCF) and high cycle failure (HCF) conditions, allowing to correlate the cycles to failure with the deformation pattern of the polymer matrix. Accordingly, two strain-approach-based fatigue models were developed and allowed accounting for the different influence of stress, and strain, concentration on the fracture behavior for static failure, LCF and HCF. To account for the variation of mechanical properties with fiber orientation, Autodesk Moldflow Insight simulations were performed, and the resulting fiber orientations were mapped into Abaqus via the mapping program Autodesk Helius. The model was validated by utilizing it for the prediction of the fatigue life of a complex shape part, showing a maximum error equal to 13.7%, in comparison to experimental results.