Through-the-thickness reinforcement for composite structures: A review

Three-dimensional preforms have been developed in order to remedy and minimize the out-of-plane damage caused by 2D structures. Several researches have been done on more complex structures which have more interesting mechanical characteristics through-the-thickness. A wide spectrum of 3D textile technologies encompassing weaving, knitting, stitching, z-pinning, tufting, etc. is used to manufacture through-the-thickness reinforced materials. This kind of reinforcement aims to achieve a balance between the in-plane and out-of-plane properties. Recently, tufting shows more opportunities to develop through-the-thickness reinforcements especially with the advances in devices from manual to fully automatic. In literature, the mechanical behaviour of tufted composites has been one of the main subjects, however, few studies outline the mechanical behaviour of dry tufted fabrics. Dry stage is an essential step to understand the influence of through-the-thickness reinforcement and the formability of multilayer preforms. In this context, the present paper reviews the various technologies of through-the-thickness reinforcement as well as the microstructural defects related to both the impregnation and the kind of reinforcement. Also, this work highlights the mechanical performance of tufted 3D structures at dry and composite scales.