Research On Fiber Fracture Mechanism In The Process Of Continuous Fiber Reinforced Thermoplastic Composite

Most of the advanced resin matrix composite materials are first manufactured to continuous fiber reinforced composite prepreg by the method of pultrusion. Then the prepregs are molding into the target product by several processing, such as injection molding, compression molding, molding process of RTM and so on. Nowadays, there is a lot of achievements in scientific research for the preparation of prepreg, including the impregnation theory, interfacial bonding and so on. And the research of continuous fiber composite fracture during processing has rarely studied. The mechanism of fiber fracture in the composite processing are still stayed at the experience level, which cannot describe the influence of processing parameters and structure parameters on the fiber fracture in the process of impregnation accurately.1. We made continuous glass fiber reinforced polypropylene composite material prepreg by pultrusion to study the movement of fiber bundle during the processing. And then the stress on the fiber bundle is analyzed in the mold which is full of melt according to the basic equations and the restriction conditions. Finally, a model of fiber fracture has been established combining the probability distribution function (the two parameters Weibull distribution) on the basis of the matrix parameters (resin viscosity), fiber property parameters (Weibull parameters), processing parameters (stay time, pin number, die temperature), and die structure parameters.2. The effect of processing variables such as roving pulling speed, melt temperature and number of pins on the porosity of prepreg and fiber fracture was studied using the self-designed mold during the process of melt impregnation when manufacturing the continuous glass fiber reinforced polypropylene prepreg. The established model of fiber fracture is verificated by the experimental data. Then the optimal parameters of this process under the condition of this experiment were obtained by the orthogonal experimental design. Finally, a processing range, which can be a guidance for industrial production in the pultrusion to manufacture continuous glass fiber reinforced polypropylene composite material prepreg, was obtained.3. Effect of the pellets shape (sheet and strip material) and fiber content on the residual fiber length of injection molded parts and mechanical property were studied. And the influences of melt temperature and fiber content on the fiber orientation and residual fiber length in products was studied by the Moldflow simulation software. The comparisons between simulation results and the experimental data was made.