Nanomechanical studies of the compressive behavior of carbon fibers

Excerpt

Carbon fiber reinforced plastics (CFRP) are subjected to compressive or bending loading in many structural applications. The mechanical behavior of the CFRP in the compressive range depends on the mechanical behavior of the carbon fibers. Thus, the compressive behavior of carbon fibers is of great interest and investigated in many articles see, e.g., [1‐5]. The nano-structure of the carbon fibers is formed by so called carbon crystallites [2, 6‐9] ,i.e., stacks of imperfect graphene layers. In [2] the influence of structural properties, like crystallite size and crystallite orientation, on the compressive behavior of carbon fibers is investigated using X-ray diffraction. Furthermore, it is assumed that carbon fibers fail by the occurrence of crystallite buckling. The non-Hookean behavior of fibers tested using the loop test is also related to buckling of the carbon crystallites [1]. The occurrence of crystallite buckling in fibers subjected to compressive loading is also assumed in [4, 5]. Experimental proof of this assumption is found in [8], where crystallite buckling of fibers is directly observed using microbeam X-ray diffraction. In the present study, the compressive behavior of single carbon crystallites is investigated using the finite element method. The aim is to better understand the influence of crystallite buckling on the overall compressive behavior of the fibers. …