Simulation of Wrinkling during Bending of Composite Reinforcement Laminates

Abstract

When a thick laminate is subjected to bending, under certain boundary conditions, wrinkles may appear and develop due to the inextensibility of the fibers. Wrinkling is one of the most critical defects in composite manufacturing. Numerical simulation of the onset and growth of such wrinkles is an important tool for defining optimal process parameters. Herein, several bending experiments of thick laminates are presented. They were found to lead to severe wrinkling and delamination of different kinds. It is shown that the history of loading changed the developed wrinkles. Stress resultant shell finite elements specific to textile reinforcement forming show their relevance to provide, for these wrinkles induced by bending, results in good agreement with the experiments, both with regard to the onset of the wrinkles and to their development. This numerical approach was used to improve the understanding of the phenomena involved in wrinkling and to define the conditions required to avoid it in a given process.

Analysis and Modeling of Wrinkling in Composite Forming

“…The manufacturing processes for preforms and prepregs often involve folding or bending of laminates. Depending on the boundary conditions, these bending operations are conducive to the development of wrinkles in the laminate [49,88,89]. It is important to be able to predict the onset and development of these wrinkles through numerical simulations.…”

“…The lay-up sequence of different layers of multilayer composite reinforcements has a significant influence on the development of wrinkles. Figure 10 shows the experiments and simulations of the deformed shapes of multilayer stack under different orientation of textile reinforcements during the symmetrical bending [89]. As the layers are oriented in [0 • /90 • ] 10 , the inextensibility of fibrous reinforcement results in a large wrinkle during the bending process (Figure 14a).…”

“…The generation of wrinkles during the bending of multilayer composite reinforcements is strongly associated with the out-of-plane pressure to which they are subjected. Figure 15 presents the deformation of multilayer stack during the L-flange forming under different loads [89][90][91][92]. When a small load (1 N) was applied at the left end of the reinforcements, no wrinkles were created, and a natural bevel was formed (Figure 15a).…”

“…These phenomena are well depicted in the simulation by the stress resultant shell elements presented in Section 2.4.2. Other cases of analysis of wrinkles during laminate bending are given in [89]. As the compression load at the left end continued to increase from 0 N to 20 N, the slippage between layers was constrained, leading to the generation of wrinkles during the bending process (Figure 15b,c).…”

Textile Composite Damage Analysis Taking into Account the Forming Process

“…Because the textile reinforcements are thin, some approaches consider them as membrane where the bending stiffness is considered low enough to be neglected [ 36 , 37 , 38 , 39 , 40 , 41 ]. It has nevertheless been shown that the bending stiffness of the textile reinforcement plays an important role in particular on the development of wrinkles [ 14 , 42 , 43 ]. In this article, the objective of the forming simulation is mainly the determination of warp and weft yarns angle variation, which is related to the membrane deformation of the textile reinforcement.…”