Abstract
Carbon nanotube/polymer nanocomposite plate- and shell-like structures will be the next generation lightweight structures in advanced applications due to the superior multifunctional properties combined with lightness. Here material optimization of carbon nanotube/polymer nanocomposite beams and shells is tackled via ad hoc nonlinear finite element schemes so as to control the loss of stability and overall nonlinear response. Three types of optimizations are considered: variable through-the-thickness volume fraction of random carbon nanotubes (CNTs) distributions, variable volume fraction of randomly oriented CNTs within the mid-surface, aligned CNTs with variable orientation with respect to the mid-surface. The collapse load, which includes both limit points and deformation thresholds, is chosen as the objective/cost function. An efficient computation of the cost function is carried out using the Koiter reduced order model obtained starting from an isogeometric solid-shell model to accurately describe the point-wise material distribution. The sensitivity to geometrical imperfections is also investigated. The optimization is carried out making use of the Global Convergent Method of Moving Asymptotes. The extensive numerical analyses show that varying the volume fraction distribution as well as the CNTs orientation can lead to significantly enhanced performances towards the loss of elastic stability making these lightweight structures more stable. The most striking result is that for curved shells, the unstable postbuckling response of the baseline material can be turned into a globally stable response maintaining the same amount of nanostructural reinforcement but simply tailoring strategically its distribution.
Highlights
Thin-walled, lightweight composite structures are commonly used in a wide range of engineering applications, in aerospace engineering, where they are often employed as primary structural components
- OPT2: optimization across the mid-surface, i.e., the volume fraction of randomly oriented carbon nanotubes (CNTs) is kept constant through the thickness but can vary within the shell mid-surface with a constraint on the overall CNTs volume;
The optimal CNTs distribution leads to the suppression of the snap-through instability, at the cost of initial stiffness reduction for low φC, reduction that becomes negligible for higher volume fractions
Summary
Thin-walled, lightweight composite structures are commonly used in a wide range of engineering applications, in aerospace engineering, where they are often employed as primary structural components. Many optimization strategies proposed in the literature use the linearized buckling load as the objective function of the design In this case, structures may suffer another elastic limit state (i.e., static bifurcation) known as buckling mode interaction, which leads to an unstable post-critical behavior [15] and a high sensitivity to imperfections, resulting in a deterioration of their load-bearing capacity due to geometrical, load and material deviations. For this reason, a more reliable design, which takes into account the geometrically nonlinear behavior, has been investigated in previous works.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
