Co-authors​ :

 Jian HU (FRANCE), Xavier LEGRAND (FRANCE), Peng WANG (FRANCE) 

Driven by the growing demand for lightweight structures, textile-reinforced composites have increased in popularity, benefiting from their high specific mechanical performances and the designability of structures. Especially for the multi-layered textile composites, due to its thick and high suitability for different environment . Forming technology is an effective and useful method to keep excellent mechanical properties of fabric and with the development of forming process in composites, the complex shapes without forming defects have been gaining more and more attention in the aerospace, transport, energy, civil engineering industry and other fields, and they can contribute to the production of stronger composite parts [1-4].
In this paper, we investigated a new textile preform by trimming the glass fiber preform to reduce the forming defects. A set of experimental investigations concerning the forming behaviors of the trimmed glass fiber performed with different forming shapers at the dry fabric scale, as presented in Fig.1. To optimize the forming process, different positions of trimming, the length of trimming and the pressure of the bland-holder affect the formability behaviors or forming defects. To quantify and evaluate the forming process, the wrinkling phenomenon, material draw-in, shear angle, punch force and misalignment of fibers are proposed. The modeling data for three-dimensional reconstruction is extracted from a stack of photographs taken around the samples, and the photos were processed by the software of ImageJ. The characteristics of wrinkles are measured by the number of wrinkles and the height of the shape compared to the surface. The formability analyses were performed in the hemispherical forming processes, the presence of trimming modified the wrinkling phenomena of the deformed preform. An increase in the trimming length can weaken the wrinkling defects. The wrinkles, material draw-in, shear angle and punch force were reduced as the length of the trimming increased. On the other hand, the misalignment of fibers was also reduced as the length of trimming increased, but this increased the misalignment of the edge of the fabric and had no significant influence on the punch zone. The position of trimming changes the edge of the material draw-in and the shape of the edge after forming. The discussion about the consistency between trimmed length and trimmed position shows that trimmed is effective in reducing forming defects. From the point of view of economics, trimming can lower the production costs of preforms with complex shapes. At present, the research object of this paper is the trimmed single-layer fabrics, as the trimmed multi-layer fabrics have not yet been studied. Consequently, the optimization of the trimmed multi-layer fabrics to minimize forming defects will be one of the important future works.