Relationship between Crystalline Structure of Polyamide 6 within Carbon Fibers and their Mechanical Properties studied using Micro-Raman Spectroscopy

ABSTRACT We aim to determine the relationship between the local crystalline structure of polyamide 6 (PA6) within carbon fibers (CFs) and the mechanical properties of unidirectional CF-reinforced PA6 composites. Two types of CFs with different surface profiles (one smooth and one rough), used as reinforcements, were employed for the transverse Charpy impact test of unidirectional PA6/CF composites. The surface profile of CF influenced the impact strength and debonding appearance. The crystalline structure of PA6 within CFs was investigated using micro-Raman spectroscopy with a spatial resolution of 1 μm. Based on the Raman study, it was suggested that the impact strength and debonding appearance were attributed to the varying polymorphism (α-phase, mesomorphic β-phase, and γ-phase crystal) of the PA6 matrix between the interface and locations away from the interface (i.e., the bulk region), depending on the surface profiles of CF.