Fan Xu's blog

Wrinkles are commonly observed in uniaxially stretched rectangular sheets with clamped-clamped boundaries, and can disappear upon excess stretching. Here we explore this wrinkling and restabilization behavior both analytically and numerically. We find that Poisson’s ratio plays a crucial role in the wrinkling and restabilization behavior. Smaller Poisson’s ratio makes later onset of wrinkling, lower amplitude and earlier disappearance of wrinkles.

Wrinkles commonly occur in uniaxially stretched rectangular hyperelastic membranes with clamped-clamped boundaries, and can vanish upon excess stretching. Here we develop a modeling and resolution framework to solve this complex instability problem with highly geometric and material nonlinearities. We extend the nonlinear Foppl-von Karman thin plate model to finite membrane strain regime for various compressible and incompressible hyperelastic materials.

When you push up your sleeves, wrinkles form, which eventually evolve into ridges (pictured). As familiar as you may be with this phenomenon, have you ever thought about its underlying mechanism? It involves the complex nonlinear mechanical behaviour of large deformations and surface instabilities, which in turn give rise to a sophisticated morphological evolution. And now, Yifan Yang and co-workers have revealed a hitherto unknown post-buckling behaviour that involves multiple bifurcation transitions (Phys. Rev.

Photo-chromic liquid crystalline polymer (LCP) is a type of smart materials which are sensitive to light. Here we harness its photo-mechanical response to flexibly control surface patterning, through modeling a film involving homeotropic nematic liquid crystals with director perpendicular to the polymer film attached on a compliant substrate. Theoretical and numerical analyses were conducted to explore the surface instability of such film/substrate systems under both uniform and non-uniform illuminations by ultraviolet (UV) light, respectively.

There has been a strong and recent research activity to obtain tunable wrinkling patterns in film/substrate systems, which proposes to use geometric curvature as a control parameter. This paper studies core-shell cylindrical systems under thermal loads, with the aim to describe possible wrinkling modes, bifurcation diagrams and dimensionless parameters influencing the response of the system.

Cross-linked liquid crystalline polymers (LCPs) are smart materials for large light-activated variation or bend to transfer luminous energy into mechanical energy. We study the light-induced behavior of homeotropic nematic network polymer plates. The perturbation method is applied to find approximate solutions under uniform illumination and compared with finite element simulations. Moreover, situations of nonuniform laser illumination are investigated.

Recent interests in curvature- and stress-induced pattern formation and pattern selection motivate the present study. Surface morphological wrinkling of a cylindrical shell supported by a soft core subjected to axial compression is investigated based on a nonlinear 3D finite element model. The post-buckling behavior of core-shell cylinders beyond the first bifurcation often leads to complicated responses with surface mode transitions. The proposed finite element framework allows predicting and tracing these bifurcation portraits from a quantitative standpoint.

Dear Colleagues,