Investigation of the out-of-plane load-bearing capacity of T1100/5405 composite T-stiffened panels.

With the continuous improvement of the mechanical properties of composite materials, the adhesive interface performance of composite T-stiffened panels has become a critical factor in determining the overall structural strength. However, little work has been reported on the mechanical properties of adhesive interfaces in composite T-stiffened panels under lateral bending and shear loading. Especially, there is no clear explanation on the damage evolution law of structural properties for the interface with defects, which greatly influenced the use of T-stiffened composite structures. In this paper, the mechanical properties of T1100/5405 composite T-stiffened laminates under lateral bending and shear loading are experimentally and numerically investigated. The load-bearing capacities for the panels with intact and defected adhesive interfaces are compared, the damage evolution law of typical T-stiffened structures is further explored. Based on the continuum damage model (CDM) and the cohesive zone model (CZM), the constitutive models of the adhesive layer and the composite material are established respectively. Good agreements between experimental and numerical profiles illustrate that damages mainly occur on the loading side and the corner of the L-type ribs under lateral bending conditions, while damages extend from both sides of the interface layer to the center under shear loading. When a prefabricated defect exists, damages extend from the defect location along the loading direction. At the same time, the analysis shows that the lay-up of the surface layer, the chamfer radius, and the width of T-type ribs have a great influence on the structural load-bearing capacity, but less on the damage evolution form.