Spreading Mechanism And Experimental Research Of Large Tow Carbon Fiber

The carbon fiber structural product made of thin layer prepreg tow have better static and dynamic mechanical properties,which are widely used in aviation,construction,sports and other fields.Among the many spreading methods,the pneumatic spreading has the advantages of low cost and difficulty in breaking the fiber tow during the fiber-spreading process.Wide and thin fiber tow can be obtained by using a pneumatic spread the large-size carbon fiber bundle.Therefore,based on the analysis of the principle of pneumatic spreading,a secondary pneumatic spreading platform is used to broaden the large-size carbon fiber bundle.The mechanism of carbon fiber bundle spreading is analyzed through experiments and simulations,and the fiber tow evaluation criteria for the secondary pneumatic spreading system are preliminarily established.It provides a new and effective solution for the uniformly and thin layering of large-size carbon fiber bundle.In order to make the large-size carbon fiber bundle evenly spread,a secondary pneumatic spreading system with a jet as a pre-spreading system and a planar airflow as a secondary system was establishment.The pre-spreading system could de-bonds the slab-shaped fiber tow and breaks up the fiber bundle,so that the fiber monofilament is free from the sizing agent.The pre-spreading fiber tow is formed into the planar airflow spreader by gathering the ring to form a uniform fiber bundle.The planar airflow spreader is designed according to the Venturi principle.The airflow creates a lateral force inside the planar airflow spreader under the action of turbulence,so that the fiber bundle can be laterally widened.In addition,the planar airflow spreader can also constrain the width of the fiber stretch.By means of orthogonal experiment,though introducing the range difference and introducing the deviation parameter,the influence of jet distance,fiber tow span and fiber tow tension were analyzed parametrically.The inlet and outlet speed of the planar airflow spreader and the pressure on the diaphragm were calibrate before the test.In order to understand the mechanism of transverse broadening of the fiber and optimize the relevant flow field parameters of the flow field,the three-dimensional CFD modeling and simulation of the jet spreading fiber and the planar airflow spreader were carried out by means of multiple mesh division techniques.In order to better understand the characteristics of the internal flow field of the planar airflow spreader,the internal flow field of the spreader was simulated by the Eulerian model.The influence of boundary conditions on the flow field is analyzed by the distribution of airflow velocity in the flow field characteristics.The simulation results are verified by experiments.The simulation results are match well with the experimental results,which indicating that models of the flow field were reliable.In order to make the process of fiber-spreading more perfect,the fiber tow evaluation criteria was preliminarily established for the secondary pneumatic spreading system,and the spread fiber tow was evaluated.The results show that the system runs smoothly,the effect of the fiber-spreading is good,and the fiber damage is small.Therefore,the secondary pneumatic spreading system can be used to thin the large-size carbon fiber bundle,which those have high strength and low-price.If so,the expensive small-size carbon bundle will be replaced and the application of the carbon fiber will be further expander.