Study On Sythesized Mechanical Performance Of Single Carbon Fiber And Dispersion Of Composite Strength

Carbon fiber has been widely used in many kinds of engineering field due to its excellent mechanical and thermal property such as high strength and modulus; high corrosion resistant and fatigue endurance, and low coefficient of thermal expansion, etc. however, there has been little support from quantitative experimental measurement of micromechanics of the carbon fibers, especially in the longitudinal compressive properties and fracture toughness, based on this background, it has an important significance to analysis the synthesized micro-mechanical properties; at the same time, the tensile strength of carbon fiber filaments is more scatter for the inner and outer defects of its own, in order to research the influence of the filaments'tensile strength on the tensile strength of composite materials, shear lag model and Monte-Carlo simulation theory were adopted to establish the relation of micro-mechanical model of the carbon fiber filaments and composites, and the scatter relation of the constituent and composite was provided, and it is important for composites optimization and valutate the mechanical propetites.For the carbon fiber filaments were produced by Japan T300(TORAY Co.Ltd) and China, the mechanical property ,such as tensile strength, longitudinal compressive strength and fracture toughness were all measured by the experimental method, simultaneously, the influence of carbon fiber's tensile strength on composite was also analyzed, Taking all these aspects together, the main contents of this paper are provided as follows:1. Experimental investigation of longitudinal compressive strength of carbon fibers'with a direct measure system. Euler's formula was used to estimate the critical length which the carbon fiber filaments occurred compressive deform, for the brittleness of the carbon fiber, during the compressive process, the filament's deform is very small, so it is very difficult to get the compressive force by a direct way, for the purpose of getting the force, the strain foil was clued on the cantilever beam, in this way, the strain of the cantilever beam could be obtained, and the carbon fiber's strain and force also can be gotten by the uilibrium condition.2. Fracture toughness of PAN-based carbon fibers estimated by experimental method. In order to obtain fiber filaments with a variety of strength, it is very difficult to manufacture accurately the surface defect by rubbing with an abrasive or by an etching reaction to them during chemical vapor deposition of TiC or TiN, in this paper, focused ion beam was used to corrosion the defects of the samples, based on this, the fracture toughness KIC of the carbon fiber were gotten by strength-mirror size relation.3. Experimental investigation on the tensile strength of carbon fiber. Carbon fiber is brittle and has the weak link for its own defects; they are to be seen in the scatter strength and volume effects, at the same time, the tensile properties is different because the micro-structure of weak link is different, in this paper, the tensile strength and modulus were cluster analysis using the Weibull distribution model and Gauss distribution model; during the experimental process, it could be seen that the longer the the sample is, the tensile strength is higher; the thinner the diameter, the tensile strength is higher, so the volume effects were researched by the sample's length and diameters.4. Tensile strength's scatter relation of carbon fiber filaments and composite materials. It plays an important role that the influence of carbon fibers'tensile strength on the macro-mechanical properties of composites, including residual stress, interface's modules and strength, the longitudinal tensile strength of composite was predicted by using the shear lag model and Monte-Carlo simulate method, and assumed that the carbon fiber failure probability obeyed two parameter Weibull model, after that, the tensile strengths of composite were analyzed by Weibull and Gauss model, then compared the analysis result of the two model, and gained the scatter relation of carbon fiber filaments and composites.