Experimental and Numerical Analysis of Curing Deformation in Hybrid Composite T‐Stiffeners Considering Viscoelasticity of Materials

Hybrid composites T‐shaped stiffeners fabricated from unidirectional tape and woven fabric prepregs are susceptible to curing deformation and residual stress redistribution during the curing and bonding process. However, existing models have limited capability to simultaneously capture viscoelastic behavior and multimaterial tool effects of T‐stiffeners. A multiscale homogenization method integrated with viscoelastic constitutive was established for both unidirectional tape and woven fabric composites, which the prediction error of axial modulus is 1% comparing with the average of experimental results. Furthermore, a sequentially coupled thermo‐chemical and mechanical model for deformation prediction during the curing and bonding process was further developed and validated against the experiment of T‐stiffeners. The model yields a maximum deviation of 10.5% in the overall deformation magnitude compared with the experimental measurements. Subsequently, the effect of tool configuration and stress relaxation of T‐stiffeners during the curing and bonding process was calculated with the validated FE model. It was found that different flexible tool configurations influence the magnitude and distribution of deformation through interfacial shear stress. Moreover, the numerical results based on the FE model found the stress relaxation during the bonding process drives an equilibrium transition of the internal stress generated in the curing process, decreasing the stress level from approximately 6.61 MPa to 4.27 MPa, which represents a reduction of about 35.4%. The findings demonstrate that viscoelasticity is necessary for capturing the key physics of dimensional stability in hybrid T‐stiffeners undergoing secondary thermal exposure.