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Kai Yu's picture

Journal Club for January 2023: Design and 3D Printing of Continuous Fiber Composites: Status, Challenges, and Opportunities

Design and 3D Printing of Continuous Fiber Composites: Status, Challenges, and Opportunities

Kai Yu

Associate Professor, Mechanical Engineering, University of Colorado Denver

 

1. Introduction

Continuous fiber-reinforced polymer composites, with their superior combination of stiffness, strength, and lightweight, have been leading contenders in various applications ranging from aerospace to ground transportation. 

lijianyu's picture

Journal Club for June 2020: Mechanically instructive biomaterials: a synergy of mechanics, materials and biology

 

Mechanically instructive biomaterials: a synergy of mechanics, materials and biology

Zhenwei Ma, Jianyu Li

Department of Mechanical Engineering, McGill University, Montreal, Canada

 

Michael S. Sacks's picture

POST-DOCTORAL FELLOW IN NEUROVASCULAR MECHANICS

The Department of Neurology, Dell Medical School, and the James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute, have a jointly administered opening for a Post-doctoral Fellow in the area of Neurovascular mechanics derived from clinical images.

 

Project:

Joshua's picture

Magneto-thermomechanically reprogrammable mechanical metamaterials

We developed a method enabling a single material system to transform with untethered, reversible, low-powered reprogrammable deformations and shape locking via the application of magneto-thermomechanically triggered prestress on the Shape Memory Polymers (SMPs) and structural instability with asymmetric magnetic torque.

Xavier Morelle's picture

Rheological investigation and modeling of healing properties during extrusion‐based 3D printing of poly(lactic‐acid)

Dear fellow iMechanicians,

Here is our recent paper that studies and models the rheological behavior of PLA deposited by 3D printing and allows to highlight the important process parameters than enable a full healing of the interface between printed layers.

Abstract

vacary's picture

Call for papers. JTCAM Journal of Theoretical, Computational and Applied Mechanics

Dear members of iMechanica, We are very pleased to announce the good health of the first overlay journal in Solid Mechanics, the so-called "Journal of Theoretical, Computational and Applied Mechanics" Journal of Theoretical, Computational and Applied Mechanics" which is a scholarly journal, provided on a Fair Open Access basis, without cost to both readers and authors. The Journal aims to select publications of the highest scientific caliber in the form of either original research or review in Solid Mechanics.

Study on Failure Process of Concrete Beams Based on A New Model of Truss Element

The new model of truss element is based on the same stress-strain curves of tension, compression, and shear with the hexahedron element under the equivalent external force. Comparing and analyzing a simply supported elastoplastic concrete beam with initial cracks by using the new element method and the finite element method, it can be found that the load-displacement curve, the load-crack opening displacement curve, the contour of the displacement under the various loads, and the distribution of the horizontal normal stress under the maximum load are all in good agreement.

A new model for elasto-plastic analysis of concrete

For the plane stress problem and the spatial problem of the elasto-plastic analysis of concrete, a new truss element model is presented by using the deformations under the equivalent external forces are the same. Some examples is given, which is in good agreement with the calculation results of the solid element.

(Note: The model in this article is the world's top concrete model, much better than the concrete model provided by Ansys itself.)

Eran Bouchbinder's picture

Bridging necking and shear-banding mediated tensile failure in glasses

The transition between necking-mediated tensile failure of glasses, at elevated temperatures

and/or low strain-rates, and shear-banding-mediated tensile failure, at low temperatures and/or

high strain-rates, is investigated using tensile experiments on metallic glasses and atomistic simula-

tions. We experimentally and simulationally show that this transition occurs through a sequence of

macroscopic failure patterns, parametrized by the ultimate tensile strength. Quantitatively analyz-

Eran Bouchbinder's picture

Brittle‑to‑ductile transitions in glasses: Roles of soft defects and loading geometry

Understanding the fracture toughness of glasses is of prime importance for

science and technology. We study it here using extensive atomistic simulations in

which the interaction potential, glass transition cooling rate, and loading geometry

are systematically varied, mimicking a broad range of experimentally accessible

properties. Glasses’ non-equilibrium mechanical disorder is quantified through

Ag, the dimensionless prefactor of the universal spectrum of non-phononic

Joshua's picture

Inverse design of 3D reconfigurable architected materials

We developed an inverse design method for constructing 3D reconfigurable architected structures — we synthesized modular origami structures whose unit cells can be volumetrically mapped into a prescribed 3D curvilinear shape followed by volumetric shrinkage for constructing modules. After modification of tubular geometry, we searched modular origamis’ geometry and topology for target mobility using a topological reconstruction of modules.

Hsiao-Wei Lee's picture

Dynamic Equilibrium Equations in Unified Mechanics Theory

Traditionally dynamic analysis is done using Newton’s universal laws of the equation of motion. According to the laws of Newtonian mechanics, the x, y, z, space-time coordinate system does not include a term for energy loss, an empirical damping term “C” is used in the dynamic equilibrium equation. Energy loss in any system is governed by the laws of thermodynamics. Unified Mechanics Theory (UMT) unifies the universal laws of motion of Newton and the laws of thermodynamics at ab-initio level.

Hsiao-Wei Lee's picture

Predicting high cycle and ultrasonic vibration fatigue with unified mechanics theory

The unified mechanics theory (UMT) is ab-initio unification of the second law of thermodynamics and Newton's universal laws of motion, in which Boltzmann's second law of entropy formulation governs dissipation & degradation. Hence, the unified mechanics theory does not require any empirical dissipation & degradation potential function or an empirical void evolution function. Material degradation is quantified on the Thermodynamic state index (TSI) axis based on the specific entropy production, which starts at zero and asymptotically approaches one at failure.

Hsiao-Wei Lee's picture

Modeling fatigue of pre-corroded metals with unified mechanics theory

The unified mechanics theory (UMT) was used to develop a model to predict the fatigue life of pre-corroded steel samples with BCC structure. Details of the experimental validation are also provided.

https://doi.org/10.1016/j.matdes.2022.111383

Zhaohe Dai's picture

Peeling by pulling: In situ SEM blister test on nanoflakes

Dear iMechanicians,

I want to share our recent work published in Nano Letters on the blister test of nanoflakes. The title, abstract, and links for data are as follows:

Pull-to-Peel of Two-Dimensional Materials for the Simultaneous Determination of Elasticity and Adhesion 

Zheng Fang, Zhaohe Dai*, Bingjie Wang, Zhongzheng Tian, Chuanli Yu, Qing Chen, and Xianlong Wei*

Fan Xu's picture

Wrinkling of twisted thin films

Thin films usually exhibit instabilities and yield intricate wrinkles when two clamped ends are twisted. Here, we explore the wrinkling behavior and pitch-fork bifurcation of twisted thin films experimentally and theoretically. To quantitatively predict the post-buckling evolution of twist-induced wrinkling morphology, we develop a refined finite-strain plate model derived from 3D field equations and then solve it by using the finite element method with COMSOL. We examine the effects of aspect ratios and pre-tension on the wrinkling profile.

Joshua's picture

Coupling of a magnetic field with instability

A bistable curved beam with magnetic torque-driven actuation has the potential for fast and untethered reconfiguration of metamaterials. However, no modeling method of a bistable curved beam whose instability is coupled with an external magnetic field for the design of active metamaterials. A bistable curved beam's second mode (S-shape) generation is essential for a multimodal and multistep reconfiguration of metamaterials, which was not explored before.

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