Fan Xu's blog
Computing wrinkling and restabilization of stretched sheets based on a consistent finite-strain plate theory
It was reported both in experiments and computations using some classical plate theories that wrinkles can appear in a uniaxially stretched rectangular hyperelastic film with clamped-clamped boundaries and can be suppressed upon further tension. Here, based on a recently-available consistent finite-strain plate theory, we investigate this complex instability problem with isola-center bifurcation (the nontrivial solution curve begins and ends at two distinct points on the trivial line) in more depth and present an efficient numerical algorithm.
Mathematically exploring wrinkle evolution
Wrinkling is one of the most important mechanical deformation modes (for example, buckling and crumpling) that are omnipresent in our daily life: for instance, wrinkled fingers after soaking in water for a prolonged time, the folds within the brain, and metal wrinkles after a car collision, to name a few.
Curvature tunes wrinkling in shells
Transverse wrinkles usually emerge in a uniaxially stretched elastic film and can be suppressed upon further tension, which is an instability-restabilization behavior due to the nonlinear competition between stretching energy and bending energy. Here, we show that curvature can effectively and precisely tune the wrinkling localization and amplitude.
Nanosleeves: Morphology transitions of infilled carbon nanotubes
Morphology instability of substrate-supported carbon atomic layers can be harnessed to modulate physical properties and functions, which has drawn interesting attention. Curvature would be a critical factor affecting surface morphology and its stability characteristics. Infilled carbon nanotubes, that is to say carbon monolayers with curved geometry and infilled substrates, namely nanosleeves, widely exist in the literature and have many potential applications.
Special Issue on Instability and Bifurcation in Materials and Structures comes out
Dear Colleagues,
After one-year effort, we are happy to announce that the SI on Instability and Bifurcation in Materials and Structures is now completed and comes out online (https://www.sciencedirect.com/journal/international-journal-of-non-linear-mechanics/special-issue/1089TRQ46GQ).
Oblique wrinkling patterns on liquid crystal polymer core–shell cylinders under thermal load
Smart soft materials, which can flexibly respond to external multi-physics stimuli, have attracted considerable attention over the past few years. Here, we present tunable wrinkling patterns in cylindrical core-shell systems under thermal load via the orientation of director in nematic liquid crystal polymer (LCP). To quantitatively analyze mechanical behavior and morphological evolution of LCP core-shell cylinders, we develop a core-shell model that accounts for director-induced anisotropic spontaneous strains.
Effect of surface topography on anisotropic friction of graphene layers
Tribological behavior of graphene layers has been a focus of intensive research interest since its crystal lattice structure can be exploited to achieve incommensurate contact, leading to nearly zero friction, namely structural superlubricity. However, wrinkling undulations are omnipresent on graphene and difficult to be completely eliminated, which inevitably resists superlubricity in reality. Here, we explore how the presence of surface wrinkles affects nanotribological behavior of graphene sliding systems.
Intricate evolutions of multiple-period post-buckling patterns in bilayers
Surface instability of compliant film/substrate bilayers has raised considerable interests due to its broad applications such as wrinkle-driven surface renewal and antifouling, shape-morphing for camouflaging skins, and micro/nano-scale surface patterning control. However, it is still a challenge to precisely predict and continuously trace secondary bifurcation transitions in the nonlinear post-buckling region. Here, we develop lattice models to precisely capture the nonlinear morphology evolution with multiple mode transitions that occur in the film/substrate systems.
A finite strain model predicts oblique wrinkles in stretched anisotropic films
Transverse wrinkles commonly occur in a uniaxially tensile elastic membrane and can vanish upon excess stretching. The wrinkling direction is usually perpendicular to the stretching direction under isotropic elasticity. Here, we show that wrinkles are orientable by material anisotropy, such as in fiber-reinforced or fibrous films, and the wrinkling orientation can be tuned by varying the stiffness and direction of fibers.