Dongmin Yang

The University of Edinburgh | UoE · School of Engineering

Discrete Element Method (DEM) and Smoothed Particles Hydrodynamics (SPH) are integrated to investigate the macroscopic dynamics of fluid–particle–structure interaction (FPSI) problems. With SPH the fluid phase is represented by a set of particle elements moving in accordance with the Navier–Stokes equations. The solid phase consists of physical par...

This paper presents a new concept to place continuous curved fibres for CFRP composites, which can be fulfilled by potential additive or hybrid manufacturing technology. Based on the loading condition, principal stress trajectories are generated through finite element analysis (FEA) and used as the guidance of the placement paths for carbon fibres....

This paper presents a micromechanics-based 3D finite element model for predicting the damage initiation, propagation, and failure strength of TC33/Epoxy carbon fiber reinforced polymer (CFRP) unidirectional lamina under biaxial loadings. The finite element model is generated by introducing representative volume element (RVE) with a random distribut...

This paper for the first time presents experimental results for fibre flow and void formation during 3D printing of short fibre reinforced thermoplastic composites by fused filament fabrication (FFF). Short carbon fibre T300 reinforced nylon-6 composite is selected as the printing material. X-ray micro-tomography (µCT) scans are performed on the ra...

This study investigates the thermal behaviour of discontinuous carbon fibre reinforced polyphenylene sulphide (CF/PPS), additively manufactured by material extrusion, with a focus on the effects of thermal process conditions on the degree of crystallinity, oxidation crosslinking and mechanical properties of CF/PPS from filament fabrication, materia...

Inter-fibre failure analysis of carbon fibre-reinforced polymer (CFRP) composites, under biaxial loading conditions, has been a longstanding challenge and is addressed in this study. Biaxial failure analysis of IM7/8552 CFRP unidirectional (UD) composites is conducted under various stress states. Two widely accepted failure criteria, the interactiv...

This study investigates the mechanism of fibre deposition in conventional 3D printing and presents an aligned fibre deposition (AFD) method to improve the fibre placement. The deposition mechanism reveals that the cracking of the filament in the transition zone and the torsional deformation during the steering path are the main cause of the defects...

This study presents a sequentially coupled optimisation of structural topology and fibre orientation for 3D printing of continuous carbon fibre reinforced polymer composites. Topology optimisation was first performed to obtain the geometry of the structure under a specific load, and then continuous fibres were placed along the identified principal...

The recent decades have seen various attempts at the numerical modelling of fibre-reinforced polymer (FRP) composites in the aerospace, auto and marine sectors due to their excellent mechanical properties. However, it is still challenging to accurately predict the failure of the composites because of their anisotropic and inhomogeneous characterist...

This study presents a data-driven, probability embedded approach for the failure prediction of IM7/8552 unidirectional carbon fibre reinforced polymer (CFRP) composite materials under biaxial stress states based on micromechanical modelling and artificial neural networks (ANNs). High-fidelity 3D representative volume element (RVE) finite element mo...

This study proposed a novel approach based on the 3D discrete element method (DEM) to simulate the progressive delamination in unidirectional carbon fibre reinforced polymer (CFRP) composite laminates. A hexagonal packing strategy was used for modelling 0 representative plies, the interface between different plies was modelled with one bond and sev...

This paper presents an experimental study on 3D printing of continuous carbon fibre reinforced thermoset epoxy composites. Powder-based solid epoxy was electrostatically flocked on the 1K continuous carbon fibre tow and then melted to fabricate composite filaments. The produced filament was printed using a modified extrusion-based printer which mel...

CO2–brine–rock interaction impacts the behavior and efficiency of CO2 geological storage; a thorough understanding of these impacts is important. A lot of research in the past has considered the nature and impact of CO2–brine–rock interaction and much has been learned. Given that the solubility and rate of mineralization of CO2 in brine under reser...

The phase of CO 2 present in a saline reservoir influences the change of the pore geometry properties of reservoir rocks and consequently the transport and storage integrity of the reservoir. In this study, digital rock physics was used to evaluate pore geometry properties of rocks saturated with the different phaseCO 2 -brine under reservoir condi...

‘Project code-named Humpty’ is a performative art piece involving the creation, fragmentation, and reconstruction of a 2.7 m high classically inspired sculpture. It was conceived to complement an archaeological science research project setting out to explore the use of digital scanning technologies in artefact reconstruction. The statue’s form was...

A manufacturing technique was developed to fabricate curved continuous carbon fibre reinforced composites based on 3D printing and epoxy-infusion treatment. Composite preforms were first manufactured by material-extrusion based 3D printing of continuous carbon fibre reinforced thermoplastic polyamide-6 (PA-6) filaments. Powder thermoset epoxy was a...

The emerging 3D printing technology of continuous fibres enables fibre steering and customised curved fibre paths during the manufacturing process, which could potentially enhance the mechanical properties of composites with geometric singularities. In this paper, the effect of fibre placement on the mechanical performance of open-hole composites u...

A coupled multiphase model based on computational fluid dynamics (CFD) and discrete element method (DEM) is developed to numerically investigate the extrusion-based 3D printing process of discontinuous carbon fibre reinforced polymer composites. Short carbon fibres are modelled as rigid bodies by clumping discrete spheres in DEM, while polymer matr...

This paper presents a robust ABAQUS ® plug-in called Virtual Data Generator (VDGen) for generating virtual data for identifying the uncertain materials properties in unidirectional lamina through artificial neural networks (ANN). The plug-in supports the 3D finite element models of unit cells with square and hexagonal fibre arrays, uses Latin-Hyper...

Using different phaseCO2-brine, the effect of stress corrosion on the micro-fabric, topology of the minerals and the elemental composition of saline rock was evaluated, to understand how this affect transport properties of rocks. Image analysis was used to evaluate changes in micro-fabric, topology of mineral and elemental composition from SEM imag...

The influences of loading path on the failure of unidirectional (UD) carbon fibre reinforced polymer (CFRP) composite laminae IM7/8552 are studied in this study. A 3D representative volume element (RVE) based micromechanical model is established using finite element method (FEM) to capture the coupled effects of fibres, matrix and fibre/matrix inte...

A coupled multiphase model based on computational fluid dynamics (CFD) and discrete element method (DEM) is developed to numerically investigate the extrusion-based 3D printing process of discontinuous carbon fibre reinforced polymer composites. Short carbon fibres are modelled as rigid bodies by clumping discrete spheres in DEM, while polymer matr...

This study presents a hybrid method based on artificial neural network (ANN) and micro-mechanics for the failure prediction of IM7/8552 unidirectional (UD) composite lamina under triaxial loading. The ANN is trained offline by numerical data from a high-fidelity micromechanics-based representative volume element (RVE) model using the finite element...

Understanding of the failure of composites is critical for evaluating their safety and reliability when they are in service. In this research, a combined image analysis technique using computed microtomography (micro-CT) and scanning electron microscopy (SEM) is proposed to study the microstructures, damage and failure of a hybrid unidirectional/wo...

This paper investigates the formation of manufacturing induced fibre misalignment and breakage during fused filament fabrication (FFF) 3D printing of 1K continuous carbon fibre filament. Single stripes at various turning angles and curvatures are printed by a desktop printer Prusa i3 using a specific brass nozzle and characterised using X-ray compu...

Static fatigue tests were conducted on core samples saturated with different phase CO2 to evaluate the fatigue rate and bulk modulus under constant but stepped stress increment. There was re-appearance of primary fatigue at higher stress in all the samples. In the brine saturated sample, for a 4 MPa deviatoric stress increase, there was about 89% i...

This study presents a 3D Discrete Element Method (DEM) model for the progressive failure analysis of Carbon Fiber Reinforced Polymer (CFRP) composite materials subjected to uniaxial tensile loading. Particles in the model are packed and bonded in regular patterns (hexagonal or square). The relationship between the bond stiffness and material proper...

The characteristics of structural discontinuities in the subsurface environment often play a key role in the overall behaviour of such systems and their response to externally imposed conditions. Rock joints are one of such features that constitute the heterogeneity of rock masses. Akin to other forms of discontinuities, the characteristics of rock...

Uncertainty propagation under multimodally distributed random variables, called multimodal distribution propagation for short, is a challenging problem due to the complicate probability density function of the random variables. In this paper, a general frame based on a new finite mixture model (λMM) constructed by derivative lambda probability dens...

In recent years, the discrete element method (DEM) has been used to model bulk material, especially brittle materials (such as rocks, ceramics, concrete, ice, etc.) with various mechanical properties or responses by setting serials of contact properties (such as bonds) in the particle assembly. These bonds can withstand a certain amount of force an...

This paper investigates the mechanical properties and permeability of chemically corroded rock during deep underground tunneling. Nuclear magnetic resonance tests are carried out to quantify the chemical damage of limestone samples at the microscopic scale. Coupled hydrostatic pressure-unloading tests at different unloading rates are also conducted...

Particles and particulate systems are widely encountered in various industrial applications which can be in the form of solid particles, liquid droplets and gas bubbles. Their behaviour is extremely complicated with multiscale and multiphase interactions. Actually, particulate materials are the second largest phase, only less than water, handled by...

In this paper, an effective microscopic modeling scheme is presented to analyze mechanical properties of composites with random short fibers. To this end, the displacement-load tests of the standard samples, which are acquired by cutting a short fiber-reinforced composite plate of 650 mm × 650 mm × 2.5 mm, are firstly executed under the quasi-stati...

An advancement of the discrete element method (DEM) is presented that improves simulation of seismicity in rock materials. The developed model builds on previous DEM procedures for imitating acoustic emissions and micro-seismicity in rocks. Currently, formulations that govern DEM techniques identify the breakage of inter-particle bonds and creation...

An advancement of the discrete element method (DEM) is presented that improves simulation of seismicity in rock materials. The developed model builds on previous DEM procedures for imitating acoustic emissions and micro-seismicity in rocks. Currently, formulations that govern DEM techniques identify the breakage of inter-particle bonds and creation...

An advancement of the discrete element method (DEM) is presented that improves simulation of seismicity in rock materials. The developed model builds on previous DEM procedures for imitating acoustic emissions and micro-seismicity in rocks. Currently, formulations that govern DEM techniques identify the breakage of inter-particle bonds and creation...

A numerical model is developed to simulate fluid flow conditions around a wellbore and to evaluate mechanisms governing fluid flow, pressure gradients, rock failure and the ensuing sand production. The rock material behaviour matches sandstone described by the Drucker–Prager material failure model. Conditions for erosion are governed through two cr...

This paper presents a novel approach to investigate the mechanism of progressive failure of fiber reinforced polymer composite (FRP) using a 3D model based on Discrete Element Method. The elasticity of this model has been validated by classic laminate theory and Finite Element Method with a very good agreement for lamina, cross-ply laminate and ang...

The mechanical behaviours of rock mass are influenced by the presence of cracks at the microscopic and macroscopic levels. When coupled with corrosion by chemical ions in ground water, these cracks can cause instabilities and fragmentation near the excavated surface of underground structures, such as shield tunnels, etc. This paper presents the dev...

In this study, we propose an integrated particle approach based on the coupling of smoothed particle hydrodynamics (SPH) and discrete element method (DEM) to predict the injection molding process of discrete short fibers. The fibers in the coupled SPH-DEM model are treated as non-rigid bodies to allow deformation and fracture. The interaction betwe...

To investigate the relationship between micro-defects in ceramic materials and macro mechanical properties and behaviours, a computational model of SiC ceramics with randomly oriented elliptical pores was established using the discrete element method (DEM). The effects of pore defect content and its aspect ratio on the failure mode, stress-strain c...

Nuclear Magnetic Resonance (NMR) imaging in combination with mechanical tests are carried out to investigate the influence of chemical solutions on porosity change, micro damage and macro mechanical property degradation of limestone samples under external stress. The NMR images and T2 values for compression stage, micro damages emergence stage, mic...

Particle-fluid flows with free-surfaces are commonly encountered in many industrial processes, such as wet ball milling, slurry transport and mixing. Accurate prediction of particle behaviors in these systems is critical to establish fundamental understandings of the processes, however the presence of the free-surface makes modelling them a challen...

Discrete element (DE) simulation of a ball mill with a large number of particles is challenging when each particle is considered. Similarity principle could be adopted to reduce the number of particles in a simulation whilst still maintaining the accurate flow behaviour of particles. This paper presents a scaling relationship between particle gravi...

This paper presents an assessment of three different particle based approaches for 3D modelling of fibre reinforced polymer (FRP) composite laminates with anisotropic elasticity, namely 3D Discrete Lattice model, 3D Hexagonal Close Packing model and Extended 2D Hexagonal and Square Packing model. These approaches are compared and evaluated against...

Modelling the Additive Manufacturing Process for Fibre Reinforced Polymer Composites-Preliminary Studies and Future Developments

Micro damage evolution in chemical corroded limestone samples subjected to cyclic loads is investigated using Nuclear Magnetic Resonance (NMR) system. Based on the experimental data of Magnetic Resonance Imaging (MRI), T2 values and porosity, the micro damage evolution process is visualized and analyzed. It is found that the porosity and micro crac...

A numerical study of the effects of friction conditions on the formation of dead metal zone (DMZ) is presented. The friction conditions are classified as three different cases in the form of coefficient: (1) constant coefficient of friction, (2) ‘smooth’ and ‘sharp’ change of the friction coefficient and (3) time-dependent friction coefficient. The...

The paper aims to improve existing correlations for the drag coefficient and averaged Nusselt number of an ellipsoidal particle in a fluid by additionally considering its orientation. To do so, three dimensional Immersed Boundary - Lattice Boltzmman Method (IB-LBM) simulations were carried out on a classical problem where a hot stationary ellipsoid...

The paper aims to improve existing correlations for the drag coefficient and averaged Nusselt number of an ellipsoidal particle in a fluid by additionally considering its orientation. To do so, three-dimensional Immersed Boundary-Lattice Boltzmman Method (IB-LBM) simulations were carried out on a classical problem where a hot stationary ellipsoidal...

This paper presents a new numerical approach for modelling the 3D printing process of fibre reinforced polymer composites by fused deposition modelling (FDM). The approach is based on the coupling between two particle methods, namely smoothed particle hydrodynamics (SPH) and discrete element method (DEM). The coupled SPH-DEM model has distinctive a...

This paper describes the development of Finite Element (FE) models for the study of the behaviour of unreinforced and Basalt Fibre Reinforced Polymer (BFRP) externally reinforced masonry walls under the action of in-plane seismic loading. Validated against experimental tests, the FE models were used to accurately predict the shear strength and refl...

A two dimensional particle model based on the discrete element method (DEM) is developed for micromechanical modelling of fibre reinforced polymer (FRP) composite laminae under biaxial transverse loads. Random fibre distribution within a representative volume element (RVE) is considered for the micromechanical DEM simulations. In addition to predic...

An integrated particle model is developed to study fluid-structure interaction (FSI) problems with fracture in the structure induced by the free surface flow of the fluid. In this model, the Smoothed Particle Hydrodynamics (SPH) based on the kernel approximation and particle approximation is used to model the fluid domain in accordance with Navier-...

In order to improve safety management, the stress changes of Li(Ni1/3Co1/3Mn1/3)O2 (NMC) cells are real-time monitored using non-destructive strain gauges, and the effects of gauge substrate, temperature and state-of-charge (SOC) have been investigated. The shell exhibits elastic deformation behaviour, and the strain-stress relationship is establis...

Cardiac tissue is a syncytium of coupled cells with pronounced intrinsic discrete nature. Previous models of cardiac electromechanics often ignore such discrete properties and treat cardiac tissue as a continuous medium, which has fundamental limitations. In the present study, we introduce a 2D electromechanical model for human atrial tissue based...

Underground coal gasification (UCG) is the in-situ conversion of deep underground coal to synthesis gas for heating, chemical manufacturing and power generation. UCG has been the subject of extensive pilot testing but technical and environmental concerns remain, not least its greenhouse gas emissions. An attractive solution is to combine UCG with C...

This paper presents the outcome of a feasibility study on underground coal gasification (UCG) combined with direct carbon dioxide (CO₂) capture and storage (CCS) at a selected site in Bulgaria with deep coal seams (>1,200 m). A series of state-of-the-art geological, geo-mechanical, hydrogeological and computational models supported by experimental...

Cardiac tissue is a syncytium of coupled cells with pronounced intrinsic discrete nature. Previous models of cardiac electromechanics often ignore such discrete properties and treat cardiac tissue as a continuous medium, which has fundamental limitations. In the present study, we introduce a 2D electromechanical model for human atrial tissue based...

Underground coal gasification (UCG) is an efficient method for the conversion of the deep coal resources into energy. This paper is concerned with a feasibility study of the potential of deeply lying coal seams (>1200 m) for the application of UCG combined with subsequent storage of CO2 for a site located in Bulgaria. A thermal–mechanical coupled m...

It is well known that the number of particles should be scaled up to enable industrial scale simulation. The calculations are more computationally intensive when the motion of the surrounding fluid is considered. Besides the advances in computer hardware and numerical algorithms, the coupling scheme also plays an important role on the computational...

Particle transportation in a fully developed turbulent duct flow is numerically investigated under the effect of wall-normal gravity force. The hydrodynamic modeling of the fluid phase is based on direct numerical simulation. The kinematics and trajectory of the particles as well as the particle-particle interaction are described by the discrete el...

Underground coal gasification (UCG) provides access to coal deposits that would otherwise remain unused and an attractive route to carbon capture and storage (CCS). UCG involves a minimum of two wells partly drilled into the coal seam some distance apart, and connected by a channel through which gases can flow. A discussion covers the UCG process;...