Experimental and numerical analyses of textile reinforcement forming of a tetrahedral shape

An experimental device for textile composite reinforcement forming is presented. A strongly double curved tetrahedral shape is formed by punch and die. This shape is those of the corner fitting parts used as corner brackets. The device shows that is possible to obtain such geometry by punch and die forming thanks to strong blank holder loads and an appropriate reinforcement. There is no wrinkle in the tetrahedral part of the formed shape but the six blank holders create wrinkles in the plane part of the preform. The shear angles reach 60° but there is no wrinkling in this zone. The presented forming process enables the experimental validation of a semi-discrete simulation approach. It is shown that shear angles and wrinkle shapes obtained by this numerical approach are in good agreement with the forming experiment. The computation of the shape of wrinkles after forming is necessary to check that these wrinkles do not expand to the useful part of the preform. This needs to take the bending stiffnesses into account. This is not the case when the simulation is based on a membrane approach.