MECHANICAL PERFORMANCE OF VARIABLE STIFFNESS PLATES SUBJECTED TO MULTISCALE DEFECTS

Novel manufacturing techniques that have arisen during the last decades have permitted to improve both the manufacturing quality and performance of laminates parts. Despite these improvements, such manufactured parts are not flaw-exempt, since uncertainty in the fabrication processes and in the material properties are still present. At the same time, numerical models that allow to describe the ground truth designs have been developed. Nevertheless, some defects have not been studied yet. This work aims to analyze the influence of spatially varying microscale defects on the mechanical performance of variable stiffness plates at both microscale and macroscale level. Attention has been paid to the usage of component-wise and layer-wise modeling, based on the Carrera Unified Formulation, to study the stochastic response of the micromechanical stresses and the macroscale buckling performance, respectively.

Stochastic Response of Nonlinear Viscoelastic Systems with Time-Delayed Feedback Control Force and Bounded Noise Excitation

In this paper, an approximate analytical procedure is proposed to derive the stochastic response of nonlinear viscoelastic systems with time-delayed feedback control force and bounded noise excitation. The viscoelastic force and the time-delayed control force depend on the past histories of the state variables, which will result in infinite-dimensional problem in theoretical analysis. To resolve these difficulties, the viscoelastic force and the time-delayed control force are approximated by the current state variable based on the quasi-periodic behavior of the systematic response. Then, by using the stochastic averaging method for strongly nonlinear systems subjected to bounded noise excitation, an averaged equation for the equivalent system is derived. The Fokker–Plank–Kolmogorov (FPK) equation of the associated averaged equation is solved to derive the stochastic response of the equivalent system. Finally, two typical nonlinear viscoelastic oscillators are worked out and the results demonstrated the effectiveness of the proposed procedure. By utilizing the quasi-periodic behavior and stochastic averaging method of the strongly nonlinear system, the time-delayed control force and the viscoelastic terms can be simplified with equivalent damping force and equivalent restoring force and the resonant response under bounded noise excitation can be obtained analytically. The numerical results showed the accuracy of the proposed method.