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.

The results of in-plane shear tests performed on 5-hardness satin woven carbon/polyphenylene sulphide and polyetheretherketone thermoplastic prepregs are described in this article. The experimental analyses are based on bias-extension tests performed in an environmental chamber. The results are given for different temperatures on both sides of the melting point. This range of temperature is that of the part during a thermoforming process. The effect of displacement rate is also investigated. The results are given both as load versus displacement curves and as shear-moment versus shear-angle curves. The latter data can be directly used in a thermoforming simulation code. It is shown on a forming simulation example that the temperature and the related change of the shear behaviour have strong consequences on the final composite part. In particular, wrinkles can develop when the process temperature is too low.