Off-center braiding process for complex composite preforms based on analysis of the geometric contour model of the mandrel

Abstract

The braiding process is an important process for composite fabrication. Aiming at the problem of inner fabric folds and outer fabric sparseness in the bending of the complex geometric mandrel during braiding, a control method for off-center braiding is proposed. The mathematical description of the yarn position in the braiding process under the off-center condition is carried out, solving the differential equation for the convergence length using Euler's method to obtain the convergence length at any moment. The prediction model of the yarn on the mandrel is established to describe the spatial position of the fell point in the coordinate system of the mandrel end face and the coverage rate of the preform is solved by using the coverage rate formula under the off-center condition. The braiding experiments of the two mandrels are carried out to verify the feasibility of the prediction model and the control method. The experimental results show that the prediction model of off-center braiding can ensure that the error between the predicted value and the actual value of the braiding angle is within 5°. At the same time, off-center braiding can reduce the inner coverage rate of the bending mandrel and improve the outer coverage rate, and the error of the coverage rate is controlled within 10%. The errors are mainly caused by neglecting the slip of the yarn on the mandrel and the variation of the fell point due to the yarn interaction.