The accurate preforming modelling of 3D woven fabrics is essential for their forming quality control and optimization. However, their tension-shear coupling during preforming is not considered in the existing models. To address this issue, an anisotropic hyperelastic constitutive model considering the tension-shear coupling was established for 3D woven fabrics. A picture frame tester was designed and manufactured to investigate tension-shear coupling effect. The results show that the fiber pre-tension can significantly enhance the shear resistance of 3D woven fabrics. The biaxial pre-tension of 1.5 % can increase the in-plane shear force by up to 2.25 times compared to that in the pure in-plane shear. The identified tension-shear coupling parameters were integrated into the hyperelastic constitutive model and were implemented via user subroutine in Abaqus. The model’s effectiveness was verified by the hemispherical and fan blade forming experiments. The proposed coupled model demonstrates higher prediction accuracy than the uncoupled model in terms of shear angle and force, which provides a valuable tool for the optimization of forming process of 3D woven fabric.

There is an urgent need for the application of broadband Microwave Absorption (MA) structures on the leading edges of aircraft wings, which requires the MA structures to possess both the broadband MA performance and great surface conformability. To meet these requirements, we designed and fabricated a flexible bioinspired meta-structure with ultra-broadband MA, thin thickness and excellent surface conformality. The carbonyl iron powder-carbon nanotubes-polydimethylsiloxane composite was synthesized by physical blending method for fabricating the MA meta-structure. Through geometry-electromagnetic optimal design by heuristic optimization algorithm, the meta-structure mimicking to the nipple photonic nanostructures on the eyes of moth can achieve ultra-broadband MA performance of 35.14 GHz MA bandwidth (reflection loss ≤ –10 dB), covering 4.86–40.00 GHz, with thickness of only 4.3 mm. Through simple fabrication processes, the meta-structure has been successfully fabricated and bonded on wings’ leading edges, exhibiting excellent surface conformability. Furthermore, the designed flexible MA meta-structure possesses significant Radar Cross-Section (RCS) reduction capability, as demonstrated by the RCS analysis of an unmanned aerial vehicle. This flexible ultra-broadband MA meta-structure provides an outstanding candidate to meet the radar stealth requirement of variable curvature structures on aircraft.

An efficient hyper-elastic model that can reflect the primary mechanical behaviors of Carbon-Kevlar hybrid woven reinforcement was developed and implemented with VUMAT constitutive code for preforming simulation. The model parameters were accurately determined through the uniaxial and bias-extension tests. To calibrate the simulation code, preforming experiments of hybrid woven reinforcement over the hemisphere mold and tetrahedron mold were respectively conducted to validate the proposed hyper-elastic model. The comparison between the simulations and experiments shows that the model can not only accurately capture shear angle distribution and geometry shape after deformation, but also accurately predict the force–displacement curve and potential fiber tensile failure during the preforming process. This result indicates that the proposed model can be used to predict the preforming behavior of Carbon-Kevlar hybrid woven reinforcement, and simulate its manufacturing process of complicated geometry.