Carbon fiber is the carbon content of more than 90% of the inorganic polymer fibers. Wherein said graphite fiber carbon content higher than 99%. Microscopic structure of the carbon fiber is similar to artificial graphite, is turbostratic structure.  carbon fiber spacing between each level of about 3.39 to 3.42A, each carbon atom at each level between the parallel arrangement of the graphite is not as structured, between the layers are joined together by van der Waals forces. 
Usually the carbon fibers as a crystalline structure and a two-dimensional hole orderly composition, wherein the content of the hole, the size and distribution of the greater impact on the performance of carbon fiber. 
When the porosity is below a certain threshold, the porosity of the carbon fiber composite material interlayer shear strength, flexural strength and tensile strength of no significant impact. Some studies have indicated that the mechanical properties of the material caused by the decline of critical porosity of 1% -4%. When the content of the pore volume in the range of 0-4%, the content of the pore volume increased by 1%, the interlaminar shear strength of about 7% lower. Through the study of carbon fibers and carbon fiber epoxy-amine resin laminate double Malaya's see, when the porosity exceeds 0.9%, the interlaminar shear strength began to decline. By the test that, mainly in the void between the fiber bundle and at the interface between layers. And pore content is higher, the larger the pore size, and significantly reduces the area between the laminates middle interface. When the material force, along interlaminar fracture easily, which is relatively sensitive to the shear strength of pore reason interlayer. Also at the aperture is the stress concentration area, carrying capacity is weak, when stressed, to expand the pore forming long crack, thereby destroyed.
Even with the same two kinds of porosity laminate (in the same period of conservation and the use of different methods of prepreg manufacturing methods), they also performed at a completely different mechanical behavior. Specific numerical mechanical properties with increasing porosity and decreasing different manifestations of porosity effect on mechanical properties of discrete large and poor reproducibility. Because it contains a large number of variable factors that affect the mechanical properties of the pore composite material laminate is a very complex issue. These factors comprise: the pore shape, size, position; fiber, matrix and mechanical properties of the interface; static or dynamic loads.
With respect to the porosity and pore aspect ratio, pore size distribution on the mechanical properties greater. And found a large void (area> 0.03mm2) have an adverse effect on the mechanical properties, which is attributed to the impact of crack porosity plastic interlayer region's rich.