Investigations of Cruciform Specimen Designs for Biaxial Tensile Testing of SMC

Abstract

This proceedings paper presents the investigation of different cruciform specimen designs for the characterization of Sheet Molding Compounds under biaxial loading. Biaxial tensile tests allow the investigation of damage evolution under multiaxial stress states, which is particularly interesting due to the different damage phenomena in composite materials. A key challenge is to find a suitable specimen shape, because typical cruciform specimens fail in the arms before damage occurs in the area of interest which is the area of the biaxial stress state in the center region of the specimen. For all of the introduced designs the stiffness degradation is analyzed more in detail and compared to that of a uniaxial bone specimen. For the best performing specimen which is reinforced by unidirectional reinforced tapes on the arms, the strain field is analyzed by finite element simulations, taking into account the mechanical properties of the different layers of the specimen. Especially in the center area and at critical points, strain concentrations and non-symmetrical strain distributions are analyzed and evaluated.

Keywords

• sheet molding compound (SMC)
• biaxial tensile testing
• cruciform specimen design
• unidirectional reinforcements
• stiffness degradation
• finite element simulation