Evaluation of Wrinkling and Mechanical Properties in Partial Bend-Forming of Thick CFRTP Laminate

In recent decades, the CFRTP press-forming process has drawn intense research interest because of its use in automobile and industrial equipment. However, it is still very challenging to cost-effectively fabricate large, long, and thick CFRTP parts, such as infrastructure and general-purpose structures. Therefore, the authors propose the partial bend-forming of thick CFRTP laminates via partial heating. While bend-forming has the potential for low-power heating and low-load pressing, this process always causes wrinkles in the bent area. The purpose of this paper is to clarify the effect of wrinkles in the bent area for the development of a new process that applies bend-forming. The wrinkles caused by a partial bend-forming experiment were observed, and strength and stiffness were evaluated by a 4-point bending test using L-shaped specimens containing wrinkles. Forming simulation of the partial bend-forming was also attempted. It was found that the bent section with wrinkles had lower strength but comparable stiffness compared to the bent section without wrinkles. When running forming simulations of wrinkling with delamination, it was found that the definition of the interlayer separation stress was important. The simulation results were in good agreement with the experimental results.