Processing and manufacturing mechanics of 3D woven composites influenced by Z-binder architecture

3D woven structures in composite applications are getting increasing attention due to their superior out-of-plane properties and ability to form near-net-shape preforms. However, the in-plane properties of 3D woven composites are often compromised due to manufacturing induced limitations. The through-thickness Z-binder holds the load-bearing warp and weft tows and gives the structural integrity to the 3D woven preforms. This research aims to investigate the role of Z-binder weave architecture and tension on the 3D woven preform and composite mechanical properties. 3D woven structures were developed with four different Z-binder weave architectures: 1x1 plain, 2x1 twill and 2x2 twill with orthogonal binding patterns and an angle interlock (AI) weave. The degree of binder interlacings was deliberately reduced to increase binder float length and reduce the binder waviness. Binders were incorporated in both warp and weft tow directions to alter the directions of the resin channels inside the structures. Two orthogonal structures were manufactured with different binder tensions. Dry preform compressibility and in-plane permeability were measured to explore the effect of binder in preform compaction and resin flow behaviour. Tensile and bending properties were characterised to investigate the role of Z-binder in composite mechanical properties and their failure mechanisms. Through-thickness binders were found to resist the transverse compaction of the dry preforms. Compressibility was improved by reducing the degree of binder interlacings. Preform permeability was primarily dominated by the resin channels which were created by the Z-binder interlacings. By reducing the frequency of binder interlacings, Z binder crimp % was reduced. This reduction also increased the fibre volume fractions of the composites. Both tensile and bending properties of the composites were primarily dependent on the degree of binder weave interlacings and fibre volume fractions. Angle interlock weave with minimum crimp % in Z-binder and least number of interlacings resulted in the highest modulus and strength in both tension and bending loads. Composite failure mechanisms were found highly sensitive to the loading directions. Damage modes were significantly distinctive in the binder way and its transverse directions. In both tensile and bending cases, the Z-binders were found the arrest the damage progression and delay the final failure of the composites.