The damage resistance and tolerance of flat [(0/45),/core/(45/0), ] sandwich plates with honeycomb core subjected to low-velocity impacts using hemispherical steel impactors has been investigated experimentally. The effects of impactor diameter on the impact behavior, resulting impact damage states, and residual strength under in-plane compressive loading was of particular interest. The impact responses characterized in terms of peak impact force was observed to be dependent on the facesheet type, core thickness, and impactor size, but was found to be independent of the boundary support conditions. The smaller impactor produced damage states characterized by residual dent depths that were comparable to the core thickness, accompanied by visible facesheet fractures. The larger diameter impactor produced damage states with large core damage regions but with dent depths less than the facesheet thickness. Under in-plane compressive loading, depending on the impact damage state, contrasting failure mechanisms involving net-section fracture and buckling failure were observed. A reduction in compressive strength up to 60% of the undamaged strength has been observed.

An analytical model for determining adhesive stress distributions within the adhesive-bonded single-lap composite joints was developed. ASTM D3165 ‘‘Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies’’ test specimen geometry was followed in the model derivation. In the model derivation, the composite adherends were assumed linear elastic while the adhesive was assumed elastic-perfectly plastic following von Mises yield criterion. Laminated Anisotropic Plate Theory was applied in the derivation of the governing equations of the bonded laminates. The adhesive was assumed to be very thin and the adhesive stresses are assumed constant through the bondline thickness. The entire coupled system of equations was determined through the kinematics relations and force equilibrium of the adhesive and the adherends. The overall system of governing equations was solved analytically with appropriate boundary conditions. Computer software Maple V was used as the solution tool. The developed stress model was verified with finite element analysis using ABAQUS by comparing the adhesive stress distributions.

No abstract

No abstract

The behavior of honeycomb core sandwich panels with thin composite facesheets, supported on a rigid base and subjected to static indentation using spherical steel indentors was investigated experimentally. The effects of indentor diameter on the load-indentation behavior, the resulting damage modes and associated energy dissipation were of particular interest. The maximum applied indentation levels were limited to that corresponding to the initiation of visible skin fracture. The experimental results indicated that the indentation levels corresponding to the initiation of core damage is not significantly affected by the indentor size. However, the load-indentation behavior exhibited a stiffening effect with increasing indentor size and flexural stiffness of the skin. Further, the skin fracture initiation energy and the characteristic skin-fracture length were proportional to the size of the indentor. The sandwich panels with fiberglass skins revealed the initiation of skin damage along the honeycomb cell walls, the damage mechanism propagating towards the center of the cell, coalescing into skin fracture.