G. J. Tsamasphyros, G. S. Bikakis

 

Abstract

 

GLARE is a Fiber-Metal Laminated material used in aerospace structures which are frequently subjected to various impact damages.  Hence, response of GLARE plates subjected to lateral indentation is very important. No FEM or other analytical solution of this problem is known to the authors. This paper deals with the static response of thin circular clamped GLARE plates under the action of a lateral hemispherical indentor located at their center. We propose a finite element modeling procedure for the calculation of static load-indentation curve and the first failure load and deflection due to glass-epoxy tensile fracture applicable to GLARE plates. Additionally, we further verify the validity of the analytical model for the solution of this problem which we have derived using the Ritz method in our previous work. A 3-D solid modeling procedure with ANSYS is implemented. We employ an isotropic non-linear elastoplastic material model which obeys a true stress-strain relation for aluminum. An orthotropic linear elastic material model is used for the glass-epoxy. The contact between the indentor and the plate is simulated by contact elements. We use non-linear analysis with geometric and material non-linearities. The indentor is forced to move and deform the plate incrementally. Analysis stops when first failure due to glass-epoxy tensile fracture occurs. This FEM procedure and our analytical model are applied to GLARE 2-2/1-0.3 and to GLARE 3-3/2-0.4 plates with various diameters. We compare FEM results with analytical results and their good agreement is demonstrated. Furthermore, FEM and analytical results are compared with published experimental data for the case of a GLARE 2-2/1-0.3 plate with a radius of 40 mm. Both numerical and analytical load-indentation curves and first failures agree well with the experimental values (failure load within 2% and 7%, failure deflection within 5% and 3% respectively). It is shown that our analytical results converge satisfactorily. Also, the expected governing role of the membrane in comparison with the bending stiffness is demonstrated. Finally, FEM plots of lateral GLARE plate deflections justify the axisymmetrical deflection shape considered by the authors.