Study Of The Structural Dependence Of The Distribution Of Carbon Fiber Bearing Stress

In the case of carbon fiber, the heterogeneity of radial structure leads to the distribution of stress when the fiber was applied force field. The radial structure of carbon fibers was evoluted depending on the carbonization and graphitization temperature, apparently the fibers have different modules. Therefore, the theoretical calculation of stress distribution was important to both the structure controlling of carbon fiber and the design of composites.In present study, micro focus beam Raman spectra, synchrotron wide angle X-ray diffraction measurements were performed to analysis the radial structural distribution for the first time in domestic. To calculate the stress distribution, the multi-components models was established as well as the in-situ measurements of Raman and wide angle x-ray diffraction under tension were applied for carbon fiber sample. The results indicated that:1. With the increase of the modulus of carbon fiber samples, the heterogeneity of the radial structure was increased. The proposition of the skin parts was also increased.2. G bands which at the position of 1580cm-1 in Raman spectra of carbon fiber was bathochromic with the increase of tension. It is attributed to the enlargement of the heterogeneity of radial structure. The slop of the plot of shift vs tension was named a app (apparent Raman shift factor) Which was increased with the higher modules of the sample3. For the carbon fiber samples with higher modulus, the graphite crystallites at the surface have larger size and smaller d002 space, while it shows small size and large d002 spacing in the core part.4. A complex mathematic series-parallel model was established to quantitatively simulate the distribution of the stress in the crystallite and amorphous region of the fiber. The calculated results shows that as the modulus of fiber increased, the stress in the surface of carbon fiber increased by about 1.5 times. As the larger modulus, the stress is more easily concentrated to the surface.