Design, Analysis and Testing of Sandwich T-joint Structures

This paper presents an investigation into the failure behaviour of composite sandwich T-joint structures under pulling load. A FE model of the T-joint structure was created and validated by test data for the purpose of design improvement. The critical regions were identified in and underneath the cleats, which are made to joint the base and web panels and transfer the load. Experimental and FE results showed that the T-joint failure is due to the excessive shear stress in the cleat and a combined shear and tensile stress in the adhesive layer between the composite base panel and the cleats. It was also shown that the presence of a circular cutout in the web panel near the joint reduces the failure load by 18%. The current conventional T-joint design is proved to be very effective despite of its complex manufacture. Alternative designs for low cost manufacture were therefore proposed and evaluated. One of the options proved to be an improved design to compete with the conventional one in terms of structural strength and low cost manufacture. Nomenclature Ei = ply moduluds in the i-direction Gij = ply shear modulus in the i-j plane ν12 = ply Poisson’s ratio in the 1-2 plane Xt, Xc = tensile/compressive strength in fibre direction Yt,Yc = tensile/compressive strength in transverse direction S = shear strength σ1,σ1 = ply stress in the 1or 2-direction τ12 = ply shear stress in the 1-2 plane ε1, ε2 = ply strain in the 1or 2-direction γ12 = ply shear strain in the 1-2 plane I