alternative to this is to use a bilinear spring in which the damping is ignored. Each layer of the composite was modeled using nearly 2 000 elements (Figure 4) using ANSYS commercial implicit code. Fig. 4. Structural FEM ANSYS mesh 4. RESULTS AND DISCUSSION As mentioned above, the premise of this paper is to provide an ESL model that can be used to represent the stiffness and damping properties of multilayer debonded composites. Once these two properties are solved for analytically, the adjusted properties can be input directly into finite element code and solved at a fraction of the computational cost with still maintaining reasonable accuracy. By exploiting the two proposed models this representation can be accomplished with reasonable accuracy and at a significant decrease in solve time. Figure 5 shows that, for a rigid mass, once the displacement is equal to Equation 24 then stiction occurs and the motion is halted resulting in a relaxation position in which for this case is approximately 2mm. This is however not necessarily true for flexible bodies, such as the multilayered debonded composites. This is dependent on the stiffness of the system when stiction occurs. This behaviour of a secondary motion, in the form of oscillations, is analogous to presliding motion [9] as it is for a flexible body and can be seen in Figure 6. Fig. 5. Analytical Coulombic free vibration decay of a rigid body 296
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