Force focusing in confined fibers and sheets

Wrinkles, folds and ripplocations: unusual deformation structures of confined elastic sheets at non-zero temperatures

We study the deformation of a fluctuating crystalline sheet confined between two flat rigid walls as a simple model for layered solids where bonds among atoms {\it within} the same layer are much stronger than those {\it between} layers. When subjected to sufficiently high loads in an appropriate geometry, these solids deform and fail in unconventional ways. Recent experiments suggest that configurations named {\it ripplocations}, where a layer folds backwards over itself, are involved. These structures are distinct and separated by large free energy barriers from smooth {\it ripples} of the a…

使用偏振成像和X射线计算机断层扫描对碳纤维片状模塑料进行定量纤维取向分析

Quantitative Fiber Orientation Analysis of Carbon Fiber Sheet Molding Compounds using Polarization Imaging and X-Ray Computed Tomography

本文对比了偏振成像与计算机断层扫描在碳纤维片状模塑料纤维取向分析中的应用，发现两者视觉相似但存在数值差异，并证明表层取向可代表整体取向。

Effect of strain path on deformation texture of superconducting niobium sheet

The texture of high purity superconducting niobium sheets plays an important role in the physical and mechanical properties of high purity niobium sheet that are important for manufacturing of superconducting accelerator cavities. In a particular batch of sheet metal, orientation imaging microscopy showed an inhomogeneous texture from the surface to the mid-thickness of the sheet consisting a gamma fiber, {111}<uvw>), cube fiber, {100}<uvw>), and also some components on the alpha fiber, {hkl}<110>. With uniaxial deformation, peaks on the {uvw}<111> gamma fiber evolve differently depending on t…

Insights into the Hierarchical Structure of Spider Dragline Silk Fibers: Evidence for Fractal Clustering of $β$-Sheet Nano-Crystallites

Spider dragline silk is one of the toughest materials known and understanding the hierarchical structure is a critical component in the efforts to connect structure to function. In this paper, we take the first step in elucidating the hierarchical fractal structure of $β$-sheet nano-crystallites, which form a robust self-similar network exhibiting an non-linear mechanical property. A combined small angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) study of the nano-crystalline component in dragline silk fibers from several species of spiders including, Latrodectus hesperus, …

Truncation of Periodic Image Interactions for Confined Systems

First principles methods based on periodic boundary conditions are used extensively by materials theorists. However, applying these methods to systems with confined electronic states entails the use of large unit cells in order to avoid artificial image interactions. We present a general approach for truncating the Coulomb interaction that removes image effects directly and leads to well converged results for modest-sized periodic cells. As an illustration, we find the lowest-energy quasiparticle and exciton states in two-dimensional hexagonal GaN sheets. These sheets have been proposed as par…

Transient hygro- and hydro-expansion of freely and restrained dried paper: the fiber-network coupling

The transient dimensional changes during \textit{hygro}-expansion and \textit{hydro}-expansion of freely and restrained dried, softwood and hardwood sheets and fibers is monitored, to unravel the governing micro-mechanisms occurring during gradual water saturation. The response of individual fibers is measured using a full-field global digital height correlation method, which has been extended to monitor the transient \textit{hydro}-expansion of fibers from dry to fully saturated. The \textit{hygro}- and \textit{hydro}-expansion is larger for freely versus restrained dried and softwood versus …