| Carbon fiber materials are widely used in aerospace,marine engineering,vehicle transportation,new energy and civil applications due to their advantages of light weight,high strength and high modulus,and corrosion resistance.The wettability of carbon fiber reinforced by resin in prepreg preparation process can be improved by expanding and thinning the carbon fiber bundles through the carbon fiber spreading process,so as to improve the mechanical properties of carbon fiber reinforced composite structural parts.Compared with other fiber spreading methods,air spreading method has less damage to carbon fiber bundles.It is more environmentally friendly,and has a large width and high efficiency.In this paper,the structural parameters of the flat air speller based on Venturi principle and the technological parameters of the air speller test platform are determined by combining simulation and experiment.At the same time,a method for evaluating the width and uniformity of the carbon fiber tow is proposed.The optimization and improvement ideas are provided for the expansion of large tow carbon fibers by air flow.1)After analyzing the characteristics of carbon fiber bundles and the mechanism of plane air spreading,an air spreading test platform was designed and built.It mainly includes heating box,jet prewinding fiber device and plane air spreader,as well as other necessary wire feeding device,tension monitoring device,unwinding device and winding device.Using the control board,through programming,realize temperature control,timing photography,wire feeding speed adjustment,winding speed adjustment and other functions,to ensure the stable operation of the air spreading fiber test platform.2)In order to realize the structural optimization design of the plane air spreader,the core device of the air spreading test platform,a flui-d-solid coupling simulation model was established.Taking the fiber element as the research object,the influence of the distance between two adjacent air flow gaps and the distance from the right-most air flow gap to the right wall on the flow field and the force of the fiber element of the plane air spreader was investigated.By comparison,the appropriate structural parameters of the plane air spanner are selected for the overall design of the air spanner test platform.3)In order to determine the process parameters of the air spreading test platform,the fiber spreading test was carried out.The sizing agent melts and volatilizes and disperses the monofilament by heating box and jet prefabricated fiber device.As soon as entering the plane air spreader,the carbon fiber bundles are widened by suction caused by a low pressure area near the air gaps.In order to quantify and compare the effects of process parameters on air flow spreading effect,the width and uniformity of carbon fiber spreading were quantified and calculated by timing photographing and post-processing.The influence of different wire feeding speed and air outlet pressure difference on fiber spreading effect of carbon fiber bundle was studied.Through the comparison of several groups of experiments,the appropriate process parameters of the air flow developing fiber test platform were selected.The results show that when the distance between two adjacent air flow gaps is 20mm,the distance from the right-most air flow gap to the right wall is 24 mm,the wire feeding speed of the air spreading test platform is 80 cm·min-1,and the air outlet pressure difference is 100 Pa,the carbon fiber bundle with good uniformity and full expansion can be obtained.Its broadening rate is 343.75%,and the uniformity of broadening in three stages is about 95.5%. |
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