##### Overview

Chenyang is a fourth-year PhD student of Civil Engineering within the Mechanics, Materials, and Structures Group at Northwestern University. Chenyang received a Bachelor's Degree in Road and Bridge Engineering at Southeast University in China and a Master of Engineering Science in Civil Engineering at Monash University in Australia. My current research interests include fracture behaviors of concrete and sandstone as well as fiber-concrete interactions.

Bike ride with Prof. Cusatis

##### Current Research

###### Extension of LDPM-F to Include Very Small Scale Fibers

LDPM-F has shown its effectiveness in modeling the mechanical response of fiber-reinforced concrete. However, a wider application of LDPM-F has been bounded by two of its limitations. Firstly, in LDPM-F, the length of fiber has to be similar with the aggregate size. Secondly, for fibers that have very small cross sections, the simulations using LDPM-F, in which each fiber is accounted for individually, are computationally extremely intensive. To address these issues, the extension of LDPM-F to include very samll scale fibers is implemented. By applying the small fiber algorithm, following problems can be dealt with: (1) simulations of the effect of nano- and micro-fibers whose length is smaller than the aggregate size; (2) simulations of fibers whose length is larger than the aggregate size but the LDPM system is obtained by coarse-graining the actual aggregate size; (3) simulations of fibers that have very small cross sections with less computational cost compared to the current LDPM-F.

###### Confinement Dependent Fiber Pullout and Spalling Behaviors

In LDPM-F, the fiber-matrix interaction is described at the facet where the potential crack locates, and the fiber are accounted for by material parameters which are dedicated to the mechanisms of the fiber pullout process. Also, the fibers are assumed to be straight, elastic, and have no bending stiffness. Due to this limitation, certain micro-mechanical effects cannot be captured by LDPM-F, including the plastic reforming of geometrically deformed fibers when they are pulled through the matrix. The objective of Task 8 is to formulate a high fidelity micro-mechanical model to simulate fiber inclusions in concrete. Unlike LDPM-F, the proposed model explicitly simulates each fiber as a series of beam elements which are connected head-to-tail. Such beam elements are expected to simulate the down-to-earth fiber-matrix interaction mechanisms during the fiber pullout process.

###### Discrete Modelling of Permeability Behaviour of Sandstone

A three-dimensional discrete dual lattice model is formulated to track the permeability evolution of granular rocks by accounting for the effect of porosity change and grain crushing. A mesoscale Lattice Discrete Particle Model (LDPM) is used to capture the mechanical behavior of granular rocks. LDPM simulates the heterogeneous deformation of granular rocks by means of discrete compatibility and equilibrium equations defined at the grain level. Build upon the mechanical lattice is a network of fluid transport elements, which simulates the fluid flow through intergranular pores and cracks. By coupling the mechanical and transport lattice models, the variation of permeability can be captured. The permeability model adopted in this study is based on the Breakage Mechanics theory, which is able to evaluate the variation of hydraulic conductivity due to the simultaneous loss of porosity and growth of surface area.