Mold Surface Optimization and Process Parameter Investigation for Preforming in Advanced Pultrusion of Composite Structures.

Advanced pultrusion technology for composite materials is an automated forming process that uses pre-impregnated materials as raw materials and is oriented towards the manufacturing of continuous components. It is particularly suitable for the continuous manufacturing of ultra-long components with uniform cross-sections and has a promising application prospect in the field of aviation composite materials. However, during the preforming stage, the pre-impregnated materials are prone to strain concentration and uneven thickness under the constraint of the mold surface, and in severe cases, there is a tendency to form wrinkles. Moreover, the severity of these defects is further influenced by the process parameters. In response to the above problems, this paper proposes a mold surface optimization method based on the finite element model with the goal of three-dimensional strain homogenization, which controls the thickness direction and in-plane strain within 5%, effectively improving the material deformation coordination. Furthermore, the influence law of preforming temperature, traction speed and tension on preforming quality was systematically analyzed through experimental research. It was found that the influence of each process parameter on appearance quality, thickness uniformity and internal quality all showed a trend of "improvement first and then deterioration", thus obtaining a relatively better combination of process parameters for preforming quality. The results of this study provide methodological and technical support for the research on advanced pultrusion preforming processes of complex cross-section components.