Innovative three-dimensional fabric structure with negative Poisson's ratio for composite reinforcement

This paper presents an innovative three-dimensional (3D) fabric structure for composite reinforcement. Different from most conventional 3D fabric structures, the new structure displays a negative Poisson’s ratio (NPR) effect under compression. Based on a manufacturing process developed by combining both non-weaving and knitting technologies, four NPR 3D fabric samples with different warp yarn diameters were first manufactured manually. Then, their Poisson’s ratio (PR) values under compression along the fabric thickness direction were experimentally evaluated. A geometrical model was also proposed for the theoretical calculation of PR values of these fabrics and was compared with experimental data. The good agreements were obtained between the calculation and experiment. The results show that all the 3D fabrics display NPR effect under compression, which results in a unique feature that allows the structure to concentrate itself under the compressive load to better resist the load. This special feature makes this innovative 3D fabric structure very attractive for many potential applications such as automobile, aerospace, defense and sports equipment, where impact protection can be a highly desirable property.