C.G. Wang

The physics of wrinkling in graphene membranes under local tension

The wrinkling characteristics of a rectangular graphene membrane under local tension are studied in this paper based on the continuum theory. The characteristics of the primary bifurcation and secondary wrinkling are studied to discover the physics of graphene wrinkling. The wrinkling geometry is predicted by a continuum theory model. The results reveal that the first wrinkle is formed at the primary bifurcation point. The non-uniform stretch-induced compressed effects, that originate from both the loaded portion and the clamped edges, buckle the graphene to form the first wrinkle. Secondary wrinkling is generated on the boundary of the wrinkled regions and the slack regions near the loaded portion in the post-wrinkling stage is the intrinsic nature of the wrinkling rupture and evolution of graphene. In addition, the length of the loaded portion and the aspect ratio of graphene have great effects on the wrinkling characteristics. These results are tremendously useful in understanding the intrinsic nature of the structural instability of graphene.

Functional group-guided variable frequency characteristics of a graphene resonator

The variable frequency characteristics of functionalized single-layered graphene sheets (SLGSs) are studied using molecular dynamics simulations. Two typical functional groups, the hydroxyl and carboxyl groups (–OH and –COOH groups), are considered in the vibration simulations of SLGSs. The functional groups may bend the SLGS surface into many ripples and disturb the mass distributions, which have a great effect on the variation characteristics of the SLGSs. Compared with the pristine SLGS, the SLGSs with randomly distributed functional groups have degenerated vibration characteristics, while the SLGSs regularly functionalized with groups have amazingly increased resonant frequencies. Thus we may design a functional group-guided variable frequency graphene resonator by tuning the distribution manner of the groups. Our results reveal that the resonant frequency shift of such a graphene resonator may reach 67%–135% of the resonance frequency of a bare graphene resonator. These results will give a significant guide to designing SLGS nanomechanical resonators having variable frequencies in the terahertz range.

The interactive bending wrinkling behaviour of inflated beams

A model is proposed based on a Fourier series method to analyse the interactive bending wrinkling behaviour of inflated beams. The whole wrinkling evolution is tracked and divided into three stages by identifying the bifurcations of the equilibrium path. The critical wrinkling and failure moments of the inflated beam can then be predicted. The global–local interactive buckling pattern is elucidated by the proposed theoretical model and also verified by non-contact experimental tests. The effects of geometric parameters, internal pressure and boundary conditions on the buckling of inflated beams are investigated finally. The results reveal that the interactive buckling characteristics of an inflated beam under bending are more sensitive to the dimensions of the structure and boundary conditions. We find that for beams which are simply supported at both ends or clamped and simply supported, boundary conditions may prevent the wrinkling formation. The results provide significant support for our understanding of the bending wrinkling behaviour of inflated beams.

A Novel Lattice-Based Design and Analysis of Inflatable Wing

To solve the light-weight of near space aircraft, this paper proposes a novel concept named as Lattice-Based Inflatable Wing (LBIW). Some tensioned cables are attached between the upper and lower skins to control the three-dimensional shape of the wing. Analyzing the stress distribution of the inner tensioned cables, it is beneficial to obtain an intrinsic relationship among the stress of the tensioned cables, the pressure and the thickness of the skin. Based on this relationship, a reasonable design scheme is put forward. In order to grasp the morphing characteristics of LBIW, experimental and numerical simulation approaches are adopted. This paper establishes a detailed finite element model and puts emphasis on solving the intricate nonlinear geometry and the influence on LBIW under different inflation pressure. The non-contact tests are performed to validate the concept design and the simulations in the end.

Rigid-flexible contact analysis of an inflated membrane balloon with various contact conditions

Considering the Mooney–Rivlin hyperelastic model, a semi-analytical approach is introduced to analyze the rigid–flexible contact behavior of an inflated membrane balloon between two plates with various interface conditions. This approach is based on differential formulation, and the coupling properties of equilibrium equations are well-solved. In order to verify the reliability of the proposed theoretical model, an experimental test was designed, by which some important contact characteristics and patterns (no-slip condition) were obtained. Two special phenomena were observed for the meridian stretch ratio with different friction coefficients. One is that the intersection points of all curves fall in a small interval, and the intersection of any two curves represents the same changing rate of the horizontal ordinate, resulting in the maximum difference. The other is the dividing point, where the stretch ratio decreases on the left and increases on the right due to the introduction of friction. These results provide solid guidance and support for our understanding of the rigid–flexible contact behavior of inflated membrane balloons.