Mechanical Engineering Commons^™

Comparative Analysis Of Water-Induced Response In 3d-Printed Scf/Abs Composites Under Controlled Diffusion, Samiul Alam, Md Tareq Hassan, Joshua Merrell, Juhyeong Lee

Mechanical and Aerospace Engineering Faculty Publications

Additive manufacturing (AM) or 3D printing of fiber-reinforced composites (FRCs) has garnered significant interests for its versatility in creating intricate parts and rapid prototyping due to cost-effectiveness. Although short fiber-reinforced thermoplastic composites are challenging to manufacture, their mechanical properties are enhanced. However, void formation during printing is a key issue, impacting mechanical properties and facilitating water ingress, affecting long-term durability. This work studies water diffusion characteristics and the associated hydro-aging of 3Dprinted short carbon fiber (SCF)/acrylonitrile butadiene styrene (ABS) composites with controlled water diffusion. Effects of material type (ABS and SCF/ABS), 3D printing path (horizontal and vertical filament orientation), and …

Mechanical Properties And Microstructure Of Multi-Materials Fabricated Through A Combination Of Lpbf And Ded Additive Manufacturing Techniques, Christopher J. Bettencourt

All Graduate Theses and Dissertations, Fall 2023 to Present

This research explores the use of different metals combined through 3D-printing to enhance the performance of materials, with a focus on making heat exchangers more cost-effective for renewable energy. The goal is to replace a costly high-temperature alloy with a more affordable low-temperature alloy, using metal additive manufacturing for its benefits such as less material waste, faster production, reduced weight, and the ability to print entire assemblies in one go. The study delves into a unique combination of two 3D-printing techniques, Directed Energy Deposition and Laser Powder-Bed Fusion, to create a multi-material composed of stainless steel 316L and a nickel-based …

Development, Modeling, Identification, And Control Of Tilt-Rotor Evtol Aircraft, Clayton T. Spencer

All Graduate Theses and Dissertations, Fall 2023 to Present

This thesis includes the development, modeling, identification, and control of an electric-Vertical-Take-Off-and-Landing (eVTOL) aircraft with tiltable rotors. The front two rotors have tilting capability for transition flight from vertical-take-off to forward-level flight. This work details the development of an eVTOL aircraft and the selection of sub components such as electric motors, batteries, and controllers. After the aircraft build, mathematical model is derived to describe the motion of the aircraft. Unknown parameters in the mathematical model are identified using a Least-Squares-regression (LSR) method that can handle parameter constraints. This is done using real flight data collected from the aircraft. Lastly, this …

Correlation Of Am Lpbf Processing Parameters To Grain Morphology Of Ss316l, Patrick Merighe

Student Research Symposium

Laser Powder Bed Fusion (LPBF) is a 3D printing technology that uses a recoater to spread powdered metal across a substrate. A laser then selectively fuses layers of this metal powder, intricately shaping three-dimensional objects. This process repeats, with each new layer of powder being spread across the previous layer to form a solid part.

Offshore Wind Farm Pycnocline Mixing From Varied Flow Types, Laura Lundahl

Student Research Symposium

As the demand for sustainable low carbon energy grows, offshore wind farms (OWFs) are becoming increasingly popular and are being pushed into stratified regions where a pycnocline exists (Figure 1). These wind farms may cause turbulent mixing of the pycnocline, which will harm the phytoplankton ecosystem. This project quantifies pycnocline mixing to gain knowledge of effective methods for mitigating harmful effects.

Quasi-Static Compression Performance Of Three Subscale Origami-Inspired Carbon Fiber Reinforced Polymer, Chase Mortensen

Student Research Symposium

Sandwich-structured composites are made of a lightweight core material between two thin composite panels. Variants of the Ori-Miura folding pattern have been investigated and compared to both the traditional Miura folding pattern (Fig. 1) and the more commonly used core design, the honeycomb. While the honeycomb design is favored over the Miura folding pattern and its variants due to its simple shape and better performance in compression, honeycomb cores also present drawbacks that are detrimental to the integrity of the sandwich structure. These drawbacks include, but are not limited to:

• Honeycomb cores consist of closed channels trapping moisture and heat. …

Simulating Low Gravity Particle-Laden Flow, Ryan Lewis

Student Research Symposium

No abstract provided.

High-Fidelity Turbulence Modelling Of Double-Diffusive Mixing In Buoyancy Driven Flows, Sanaz Izadifar

Student Research Symposium

Double-diffusive convection is the flow caused by buoyancy gradient in a fluid, where two different scalars cause density gradients, and each scalar has significantly different diffusion rates.

Wake Characteristics Of In-Phase And Out-Phase Array Of Oscillation Airfoils, Yi-Cheng Chen

Student Research Symposium

In order to solve the hydrodynamics of a school of fish using the open-source SEM solver Nek5000, an oscillating mesh is required to simulate fish oscillations and at the same time simplify the process of mesh partitioning and satisfy the limitation of nek5000 that the mesh must be quadrilateral.

Mechanical Property Variability In Lpbf Ss316l Due To Defects Formation And Process Interruption, Tasrif Ul Anwar

Student Research Symposium

This project aims to understand the correlation between the manufacturing process, defect formation, process interruptions, and the resulting properties of components made with laser powder bed fusion techniques.

Dynamic Angle Of Repose Of Ss316l Powders Fabricated By Gas Atomization For Additive Manufacturing Applications, S. M. Mahid

Student Research Symposium

Metal additive manufacturing (AM) techniques, unlike conventional manufacturing methods like turning and milling, construct objects by incrementally adding layers of material. Various processes can be used to 3D print including laser or electron beams to melt or sinter metallic powder particles.

A Novel Camera Based Measurement Technique For High Temperature Applications, Prasenjit Dewanjee

Student Research Symposium

Digital Image Correlation (DIC) is an optical technique for camera-based measurements.

Experimental Investigation On Flexural Behavior And Energy Absorption Of Lightweight Sandwich Panels With Aluminum Honeycomb Core Embedded By Thin-Ply Carbon-Glass Fibers/Epoxy Face Sheets, Reyhanehsadat Kazemian, Nader Fanaie, S. M. Saleh Mousavi-Bafrouyi, Juhyeong Lee

Mechanical and Aerospace Engineering Faculty Publications

Generally, designing lightweight and thin-walled structures with high mechanical performance is one of the challenging issues for mechanical and civil engineering sciences. To this aim, sandwich panels which have been designed and analyzed in present research include aluminum honeycomb core (H) and UD-thin-ply carbon (C)/glass fiber fabric (G) composite facings and investigated the effect of hybridization and stacking sequence on their static and dynamic mechanical properties while keeping thickness constant. Hybrid face sheets panels with three lay-up configurations of [G₂C₂G₂H̅]_s, [GCG₂CGH̅]_s, [CG₄CH̅]_s and non-hybrid configurations …

Stick-Fixed Maneuver Points In Roll, Pitch, And Yaw And Associated Handling Qualities, Benjamin C. Moulton, Troy A. Abraham, Douglas F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

The stick-fixed pitch maneuver point is an important measure of aircraft longitudinal dynamic response and handling quality characteristics, and includes effects of both aerodynamic and inertia properties of the aircraft about the pitch axis. In the present work, the existence of stick-fixed roll and yaw maneuver points is demonstrated, which are determined from the lateral forces, moments, and inertial properties of the aircraft. These stick-fixed roll and yaw maneuver points are directly related to the predicted lateral handling qualities. Example results are included for several aircraft that demonstrate the importance of this parameter when predicting the dynamic response of the …

Modeling Of Frontal Polymerization Of Carbon Fiber And Dicyclopentadiene Woven Composites With Stochastic Material Uncertainty, Ahmadreza Mohammad Sharifi, Dong-Jun Kwon, S. Z. H. Shah, Juhyeong Lee

Mechanical and Aerospace Engineering Faculty Publications

A novel finite element modeling framework is proposed for simulating dicyclopentadiene (DCPD) frontal polymerization in carbon fiber (CF) woven composites. A mesoscale CF/DCPD representative volume element (RVE) model was developed with two triggering directions, resulting in out-of-plane and in-plane DCPD polymerization. The Arrhenius equation coupled with a modified Prout-Tompkins autocatalytic model was used to evaluate the dynamic DCPD polymerization process. The rate and degree of DCPD cure were calculated by the material property uncertainties of DCPD with and without random void inclusions (3% used as a reference in this work). The DCPD frontal polymerization in CF/DCPD composite was strongly influenced …

Experimental And Modelling Of Lightning Damage To Carbon Fibre-Reinforced Composites Under Swept Stroke, Chengzhao Kuang, Kunkun Fu, Juhyeong Lee, Huixin Zhu, Qizhen Shi, Xiaoyu Cui

Mechanical and Aerospace Engineering Faculty Publications

Lightning swept stroke creates multiple lightning attachments along an aircraft in flight. This introduces distinct structural damage compared to that from a single-point lightning current injection test in laboratory. This study presents both experimental and numerical studies on lightning damage in carbon fibre-reinforced polymer (CFRP) composites under swept stroke. Coupled electrical–thermal finite element (FE) models were proposed to predict lightning damage to CFRP composites under single-point current injection and swept stroke, respectively. A lightning swept stroke testing method was proposed by embedding a copper wire inside the composites to simulate multiple lightning attachments on the composites. The FE-predicted damage from …

Experimental And Numerical Study Of Low-Velocity Impact Damage In Sandwich Panel With Uhmwpe Composite Facings, Bin Yang, Qi Zhou, Juhyeong Lee, Yan Li, Kunkun Fu, Dongmin Yang

Mechanical and Aerospace Engineering Faculty Publications

This paper is concerned with the low-velocity impact (LVI) response behaviour of sandwich composite panels (SCPs) with ultra-high molecular weight polyethylene (UHMWPE) composite facings and Polyvinyl Chloride (PVC)/Polyethylene Terephthalate (PET) foam cores. A series of LVI tests with SCPs subjected to 50 J, 80 J and 110 J were conducted to examine their impact characteristics and damage mechanisms. LVI-induced internal damage in the SCPs were characterised by compute micro-tomography (μCT) analysis. The effects of UHMWPE areal density and foam type on the LVI responses and associated failure modes of the panels were also examined. The experimental results showed that the …

Quantifying The Effect Of Stable Stratification On Low-Reynolds Number Flow Past A Horizontal Cylinder, Holland Kartchner

All Graduate Theses and Dissertations, Fall 2023 to Present

In this research, we study the behavior of flow around a cylinder in the presence of stable stratification, which refers to variations in density throughout the fluid. This phenomenon is observed in natural and industrial settings. We use computer simulations to analyze how stratification affects the flow patterns created by the cylinder. Specifically, we investigate situations where the stratification is perpendicular to the flow direction, and the wake exhibits two-dimensional characteristics. We use spectral-element method based computational fluids dynamics to simulate the phenomena. During the simulations, we vary two important parameters: the Densimetric Froude Number (Fr) and the …

Development, Implementation, And Optimization Of A Modern, Subsonic/Supersonic Panel Method, Cory D. Goates

All Graduate Theses and Dissertations, Fall 2023 to Present

In the early stages of aircraft design, engineers consider many different design concepts, examining the trade-offs between different component arrangements and sizes, thrust and power requirements, etc. Because so many different designs are considered, it is best in the early stages of design to use simulation tools that are fast; accuracy is secondary. A common simulation tool for early design and analysis is the panel method. Panel methods were first developed in the 1950s and 1960s with the advent of modern computers. Despite being reasonably accurate and very fast, their development was abandoned in the late 1980s in favor of …

Estimated Aerodynamic Forces And Moments And Optimal Orientation Of The V-Bat Airframe During Vertical Landing In Gusty Conditions, Parker C. Carter

All Graduate Theses and Dissertations, Fall 2023 to Present

Ship based Unmanned Air Systems (UAS) are an important tool used by the United States Navy for situational awareness and short-range operations. Naval UAS are used to provide real-time intelligence, surveillance, reconnaissance, and target-acquisition while being low cost, mission flexible, and safe. Unfortunately UAS suffer disadvantages with respect to adverse environmental conditions caused by the air being displaced by the ship. The accumulation of one or more adverse conditions is known as airwake. To counteract the effects of airwake, the objectives of this work are to first evaluate the effect of forces and moments during the vertical landing phase of …

Molecular Dynamics Simulations Of The Spontaneous Deformation And Auxetics Behavior During Tensile Test Of A Nematic Liquid Crystal Elastomer Model, Haoran Wang, Nanang Mahardika

Browse all Datasets

Nematic liquid crystal elastomers (LCEs) are advanced materials known for their shape-changing capability in response to external stimuli such as heat, light and electromagnetic fields. This makes them excellent candidates for applications like soft robotics and energy harvesting. While studies on their physical behavior have shed light on the complex nonlinear mechanics of LCEs, investigations through all-atom molecular dynamics (MD) simulations remain an underutilized avenue compared to experimental and theoretical analyses. This limited use is primarily due to the lack of well-established frameworks for conducting high-fidelity atomistic simulations of LCEs. To bridge this gap, we introduce an all-atom MD simulation …

Dynamics And Scaling Of Particle Streaks In High-Reynolds-Number Turbulent Boundary Layers, Tim Berk, Filippo Coletti

Mechanical and Aerospace Engineering Faculty Publications

Inertial particles in wall-bounded turbulence are known to form streaks, but experimental evidence and predictive understanding of this phenomenon is lacking, especially in regimes relevant to atmospheric flows. We carry out wind tunnel measurements to investigate this process, characterizing the transport of microscopic particles suspended in turbulent boundary layers. The friction Reynolds number Re_𝜏 = O(10⁴) allows for significant scale separation and the emergence of large-scale motions, while the range of viscous Stokes number St⁺ = 18–870 is relevant to the transport of dust and fine sand in the atmospheric surface layer. We …

Towards A Virtual Test Framework To Predict Residual Compressive Strength After Lightning Strikes, Scott L.J. Millen, Xiaodong Xu, Juhyeong Lee, Suparno Mukhopadhyay, Michael R. Wisnom, Adrian Murphy

Mechanical and Aerospace Engineering Faculty Publications

A novel integrated modelling framework is proposed as a set of coupled virtual tests to predict the residual compressive strength of carbon/epoxy composites after a lightning strike. Sequentially-coupled thermal-electric and thermo-mechanical models were combined with Compression After Lightning Strike (CAL) analyses, considering both thermal and mechanical lightning strike damage. The predicted lightning damage was validated using experimental images and X-ray Computed Tomography. Delamination and ply degradation information were mapped to a compression model, with a maximum stress criterion, using python scripts. Experimental data, in which artificial lightning strike and compression testing were performed, was used to assess the predictive capabilities …

On Quantifying Uncertainty In Lightning Strike Damage Of Composite Laminates: A Hybrid Stochastic Framework Of Coupled Transient Thermal-Electrical Simulations, R. S. Chahar, J. Lee, T. Mukhopadhyay

Mechanical and Aerospace Engineering Faculty Publications

Lightning strike damage can severely affect the thermo-mechanical performance of composite laminates. It is essential to quantify the effect of lightning strikes considering the inevitable influence of material and geometric uncertainties for ensuring the operational safety of aircraft. This paper presents an efficient support vector machine (SVM)-based surrogate approach coupled with computationally intensive transient thermal-electrical finite element simulations to quantify the uncertainty in lightning strike damage. The uncertainty in epoxy matrix thermal damage and electrical responses of unprotected carbon/epoxy composite laminates is probabilistically quantified considering the stochasticity in temperature-dependent multi-physical material properties and ply orientations. Further, the SVM models are …

Development Of Surrogate-Optimization Models For A Novel Transcritical Power Cycle Integrated With A Small Modular Reactor, Yili Zhang, Jacob Bryan, Geordie Richards, Hailei Wang

Mechanical and Aerospace Engineering Student Publications and Presentations

In recent years, various types of surrogate optimization models have been proposed to reduce the computational time and to improve the emulation accuracy. In this study, by leveraging an ANN surrogate model developed earlier, a comprehensive and efficient optimization algorithm is conceived for the global optimal design of an integrated regenerative methanol transcritical cycle. It combines a unique converging/diverging classifier model into the surrogate model to form a surrogate-based model, which significantly improves the prediction accuracy of the objective function. Six binary classifiers are explored and the multi-layer feed-forward (MLF) neural network classifier is selected. In addition, within the five …

Microstructural Characterization Of The Transition In Ss316l And In625 Bimetallic Fabricated Using Hybrid Additive Manufacturing, Christopher J. Bettencourt, Nadia Kouraytem

Mechanical and Aerospace Engineering Faculty Publications

Nearly all energy technologies utilize heat exchangers and recuperators within the power cycle. To further improve the cost-effectiveness of recuperators, costly high temperature Inconel 625 superalloy was substituted with a more affordable Stainless Steel 316L to be used at the low-temperature side of the heat exchanger. Bimetallic samples for analysis and examination were fabricated by combining Laser Powder-bed Fusion and Directed Energy Deposition. Two transition strategies for joining to the laser powder-bed fusion steel were explored, namely, a direct transition and an intermediate layer of 50% nickel powder mixed with 50% steel powder through Directed Energy Deposition. The microstructure and …

Bending Performance And Failure Mechanisms Of Hybrid And Regular Sandwich Composite Structures With 3d Printed Corrugated Cores, S.Z.H. Shah, Khurram Altaf, Juhyeong Lee, Tahir Sharif, Rizwan Saeed Choudhry, S. M. Hussain

Mechanical and Aerospace Engineering Faculty Publications

The effect of core geometry and hybridization on the bending performance and failure mechanisms of carbon fibre-reinforced polymer (CFRP) and glass fibre-reinforced polymer (GFRP) corrugated sandwich composite structures (SCS) were experimentally investigated using a three-point bend test. The CFRP and GFRP corrugated cores and facesheets were produced using Fused Filament Fabrication (FFF) and vacuum-assisted infusion processes, respectively. Three types of corrugated SCSs were built: SCSs with different core geometries (circular, square, trapezoidal, sinusoidal, and triangular), hybrid SCSs with different CFRP and GFRP cores and facesheets, and fully 3D-printed CFRP and GFRP SCSs. The corrugated SCS with square core geometry outperformed …

Cislunar Navigation Techniques And Navigation Performance Optimization, Quinn P. Moon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nova-C is a lunar lander developed by the private company Intuitive Machines to deliver commercial payloads to the Moon. The IM-1 mission set for 2023 will launch and land the Nova-C near the Moon's south pole. In this research, various navigation techniques are explored to determine the lander's position and velocity during key segments. This process is studied for key mission events including trajectory correction maneuvers (TCMs), lunar orbit insertion (LOI), and descent orbit insertion (DOI). Each mission segment, referred to as an Orbit Determination Segment (OD), is analyzed with three different navigation techniques: Monte Carlo Analysis, Linear Covariance Analysis, …

Multiscale Damage Modelling Of Notched And Un-Notched 3d Woven Composites With Randomly Distributed Manufacturing Defects, S.Z.H. Shah, Juhyeong Lee, P.S.M. Megat-Yusoff, Syed Zahid Hussain, T. Sharif, R.S. Choudhry

Mechanical and Aerospace Engineering Faculty Publications

This work proposes a stochastic multiscale computational framework for damage modelling in 3D woven composite laminates, by considering the random distribution of manufacturing-induced imperfections. The proposed method is demonstrated to be accurate, while being simple to implement and requiring modest computational resources. In this approach, a limited number of cross-sectional views obtained from micro-computed tomography (µCT) are used to obtain the stochastic distribution of two key manufacturing-induced defects, namely waviness and voids. This distribution is fed into a multiscale progressive damage model to predict the damage response of three-dimensional (3D) orthogonal woven composites. The accuracy of the proposed model was …

Convexity Applications In Single And Multi-Agent Control, Olli Nikodeemus Jansson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The focus of this dissertation is in the application of convexity for control problems; specifically, single-agent problems with linear or nonlinear dynamics and multi-agent problems with linear dynamics. A mixture of convex and non-convex constraints for optimal control problems is also considered. The main contributions of this dissertation include: 1) a convexification of single-agent problems with linear dynamics and annular control constraint, 2) a technique for controlling bounded nonlinear single-agent systems, and 3) a technique for solving multi-agent pursuit-evasion games with linear dynamics and convex control and state constraints. The first result shows that for annularly constrained linear systems, controllability …