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The behaviour of a hybrid bonded butt-joint, comprised of a double lap steel-GFRP and a GFRP sandwich composite part under three-point bending load is analysed through both numerical and experimental studies. The geometry of the joint is typical for marine applications and two possibilities of steel–to-composite connection are investigated: non-bolted and bolted. Deflection under the load point and strains at various locations of the joint were monitored and also numerically calculated. The tests revealed that the bolts used to connect the skin to steel do not have a remarkable effect on the joint's capacity and stiffness in bending conditions. The numerical models can contribute to predict the structural response of the joint up to the loading at which debonding initiates and also the failure location.

The deflection of the composite laminates and their maximum tensile strain in bending conditions are investigated in this study. For this purpose, different equivalent single layer and layerwise theories based on polynomial shape functions are used. Then Rayleigh–Ritz approximation technique and principle of minimum potential energy are applied to obtain the unknown coefficients of the displacement fields. The results are compared with the three dimensional finite element analysis and the experimental investigation. Also the process of obtaining material properties in tensile condition is explained completely. Regarding to the computational costs and agreement of the analytical and numerical results with the experimental ones, for both CCFF and SSFF boundary conditions the deflection prediction by layerwise HSDT is in a good consistency with the experimental results than the other plate theories and FEM method in this study. Although for obtaining strains in SSFF boundary conditions precisely FEM is more applicable.

A model of a composite-to-steel hybrid balcony overhang is tested to find its strength and stiffness under imposed shear and bending loads. The configuration tested is representative of a solution being considered for the balconies of cruise ships, where the substitution of steel by composites aims at weight saving. The steel component is a channel type of structure made of two plates that serve as external supports of the sandwich plate. A finite element model is used to compare with the experimental results and to predict the critical regions of stress concentration. The results include load-deflection and load-strain curves with the maximum value of the shear and bending loads. The critical locations and failure loads have been investigated too.

A composite-to-steel joint under bending and torsional loads is experimentally studied to determine their strength and stiffness and to calibrate numerical models with respect to the experimental measurements. The steel component is a channel type of structure made of two plates that serve as external supports of an inserted sandwich plate made of composite materials. The attachment of the steel joint to the structure is supported by a bracket. The results include load–deflection and load–strain curves, critical locations and failure loads, with the maximum value of the pure bending and combined torsion-bending moments. The good agreement between the numerical results obtained by finite element method and the experimental ones demonstrate that this kind of numerical analysis can estimate appropriately the behaviour of the structure.

A composite-to-steel butt-joint applied to joining large composite sandwich panels to steel ships is studied and its design is improved based on numerical simulations combined with test results. A cohesive zone model is adopted to simulate interfacial debonding of the joint. Cohesive property parameters of the interfaces are obtained by multiple calculations and comparisons with experimental results. Three schemes for improving the design of the joint are proposed. The numerical simulation results of the improvement schemes based on the cohesive parameters obtained before indicate that these three schemes can effectively relieve the shear stress concentration and improve the stress field on the critical region, thus delaying the interfacial debonding and the core strength failure, thus increasing the bearing capacity of the joint.

A Layerwise Higher Order Shear Deformation Theory is developed for plates containing rectangular embedded delaminations undergoing non negligible lateral deflections. The effects of different parameters of the composite laminate and delaminated area are investigated analytically under buckling load and the results are compared with the three dimensional finite element analysis. The results demonstrate the effects of different geometrical parameters of the delaminated area and thickness on the deflection of a composite laminate. Also the initiation of debonding in opening and sliding fracture modes is predicted using the developed formulation.

The effects of different parameters of the composite laminate and delaminated area are investigated analytically under buckling load based on a developed Layerwise Higher Order Shear Deformation Theory and the results are compared with the three dimensional Finite Element Analysis. The results demonstrate the consequences of different geometrical parameters of the delaminated area, lay-up sequences and thickness of the laminate on the deflection of a composite plate containing through-the-width delamination.

The deflection of composite laminates and their maximum compressive and tensile strains under in-plane compression, buckling and post-buckling conditions are investigated in this study. For this purpose, different equivalent single layer and layer wise theories based on polynomial and trigonometric shape functions are used. Then the Rayleigh–Ritz approximation technique and the principle of minimum potential energy are applied to obtain the unknown coefficients of the displacement fields. The results are compared with a three-dimensional finite element analysis and an experimental program is conducted to produce data for validation of theoretical and numerical methods. Mesh independency is also studied to evaluate the accuracy of the finite element results. Regarding to the computational costs and agreement of the analytical and numerical results with the experimental ones, the layer wise higher order shear deformation theory (LHSDT) based on polynomial shape functions is the most efficient and flexible theory in calculation of the deflection and strains for the very thin to thick laminates in the buckling and post-buckling conditions.