Department of Mechanical and Energy Engineering

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A Novel Framework for Predictive Modeling and Optimization of Powder Bed Fusion Process
(MDPI, 2021-10) Marrey, Mallikharjun; Malekipour, Ehsan; El-Mounayri, Hazim; Faierson, Eric J.; Agarwal, Mangilal; Mechanical and Energy Engineering, School of Engineering and Technology
Powder bed fusion (PBF) process is a metal additive manufacturing process which can build parts with any complexity from a wide range of metallic materials. PBF process research has predominantly focused on the impact of only a few parameters on product properties due to the lack of a systematic approach for optimizing a large set of process parameters simultaneously. The pivotal challenges regarding this process require a quantitative approach for mapping the material properties and process parameters onto the ultimate quality; this will then enable the optimization of those parameters. In this study, we propose a two-phase framework for optimizing the process parameters and developing a predictive model for 316L stainless steel material. We also discuss the correlation between process parameters -- i.e., laser specifications -- and mechanical properties and how to achieve parts with high density (> 98%) as well as better ultimate mechanical properties. In this paper, we introduce and test an innovative approach for developing AM predictive models, with a relatively low error percentage of 10.236% that are used to optimize process parameters in accordance with user or manufacturer requirements. These models use support vector regression, random forest regression, and neural network techniques. It is shown that the intelligent selection of process parameters using these models can achieve an optimized density of up to 99.31% with uniform microstructure, which improves hardness, impact strength, and other mechanical properties.
Carbon and cellulose based nanofillers reinforcement to strengthen carbon fiber-epoxy composites: Processing, characterizations, and applications
(Frontiers, 2023-01-10) Biswas, Pias Kumar; Omole, Oluwaseun; Peterson, Garrett; Cumbo, Eric; Agarwal, Mangilal; Dalir, Hamid; Mechanical Engineering, School of Engineering and Technology
Since the inception of carbon fiber reinforced polymer (CFRP) composites, different nanofillers have been investigated to strengthen their mechanical and physical properties. To date, the majority of research has focused on enhancing fiber/matrix interface characteristics and/or optimizing nanofiller dispersion within the matrix, both of which improve the performance of carbon fiber-epoxy composite structures. Nanofillers can be dispersed into the polymer matrix by different techniques or nanofillers are chemically bonded to fiber, polymer, or both via multiple reaction steps. However, a few studies were conducted showing the effects of different nanofillers on the performance of carbon fiber-epoxy composites. Here a critical study has been done to explore different carbon and cellulose-based nanofillers which are used to enhance the mechanical and physical properties of carbon fiber-epoxy composites. After giving a short history of carbon fiber production, the synthesis of carbon nanotubes (CNTs), graphene, cellulose-based nanofillers (cellulose nanocrystals and nanofibers), their dispersion in the polymer matrix, and chemical/physical bonding with the fiber or polymer have been extensively described here along with their processing techniques, characterizations, and applications in various fields.
Cross-Selectivity Enhancement of Poly(vinylidene fluoride-hexafluoropropylene)-Based Sensor Arrays for Detecting Acetone and Ethanol
(MDPI, 2017-03-15) Daneshkhah, Ali; Shrestha, Sudhir; Siegel, Amanda; Varahramyan, Kody; Agarwal, Mangilal; Mechanical Engineering, School of Engineering and Technology
Two methods for cross-selectivity enhancement of porous poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/carbon black (CB) composite-based resistive sensors are provided. The sensors are tested with acetone and ethanol in the presence of humid air. Cross-selectivity is enhanced using two different methods to modify the basic response of the PVDF-HFP/CB sensing platform. In method I, the adsorption properties of PVDF-HFP/CB are altered by adding a polyethylene oxide (PEO) layer or by treating with infrared (IR). In method II, the effects of the interaction of acetone and ethanol are enhanced by adding diethylene carbonate (DEC) or PEO dispersed in DEC (PEO/DEC) to the film. The results suggest the approaches used in method I alter the composite ability to adsorb acetone and ethanol, while in method II, they alter the transduction characteristics of the composite. Using these approaches, sensor relative response to acetone was increased by 89% compared with the PVDF-HFP/CB untreated film, whereas sensor relative response to ethanol could be decreased by 57% or increased by 197%. Not only do these results demonstrate facile methods for increasing sensitivity of PVDF-HFP/CB film, used in parallel they demonstrate a roadmap for enhancing system cross-selectivity that can be applied to separate units on an array. Fabrication methods, experimental procedures and results are presented and discussed.
DESIGN AND FABRICATION OF MULTI-FUNCTIONAL ENERGY STORAGE COMPOSITES INTEGRATING ULTRATHIN LITHIUM-ION BATTERY WITH ENHANCED ELECTRO-MECHANICAL PERFORMANCE
(EPFL Lausanne, Composite Construction Laboratory, 2022-06) Biswas, Pias Kumar; Jadhav, Mayur; Ananda Habarakada Liyanage, Asel; Dalir, Hamid; Agarwal, Mangilal
Exponential advancement in the automotive and aerospace industry promotes the need for Multifunctional Energy Storage Composites (MESCs) to minimize the dependence on fossil fuels and reduce structural weight. This study proposes and evaluates a multi-functional carbon fiber reinforced polymer (CFRP) composite with an embedded lithium-ion polymer battery, demonstrating a structural integrity concept. Here electrospun epoxy-multiwalled carbon nanotubes (epoxy-MWCNT) nanofibers were incorporated precisely on the uncured CFRP surface to enhance adequate interfacial bonding and adhesion between the layers after curing. The mechanical and physical properties of modified CFRP have been evidenced to possess higher mechanical strength than the traditional CFRP composite. Commercial ultra-thin lithium-ion battery with higher energy density has been uniquely integrated into the core of the CFRP composite structure. Comparison with conventional CFRP composite and electro-mechanical testing ensured that the electrochemical property of the embedded battery was preserved in loading/unloading conditions, and the mechanical strength of the composite structure was not compromised.
Electrospun Thermosetting Carbon Nanotube–Epoxy Nanofibers
(ACS, 2021-02) Aliahmad, Nojan; Biswas, Pias Kumar; Wable, Vidya; Hernandez, Iran; Siegel, Amanda; Dalir, Hamid; Agarwal, Mangilal; Mechanical and Energy Engineering, School of Engineering and Technology
This paper represents the process of fabrication and characterization of submicron carbon nanotube (CNT)–epoxy nanocomposite filaments through an electrospinning process. Electrospinning is one of the most versatile, inexpensive, and environmentally well-known techniques for producing continuous fibers from submicron diameter all the way to tens of nanometer diameter. Here, electrospinning of submicron epoxy filaments was made possible by partial curing of the epoxy by mixing the hardener and through a thermal treatment process without the need for adding any plasticizers or thermoplastic binders. This semicuring approach makes the epoxy solution viscous enough for the electrospinning process, that is, without any solidification or nonuniformity caused by the presence of the hardener inside the mixture. The filaments were spun using a CNT/epoxy solution with a viscosity of 65 p using 16 kV and a collector distance of 10 cm. The diameter of these filaments can be tuned as low as 100 nm with adjustment of electrospinning parameters. By incorporating a low amount of CNT into epoxy, better structural, electrical, and thermal stabilities were achieved. The CNT fibers have been aligned inside the epoxy filaments because of the presence of the electrostatic field during the electrospinning process. The modulus of the epoxy and CNT/epoxy filaments were found to be 3.24 and 4.84 GPa, respectively. The presence of the CNT can lead up to 49% improvement on modulus. Accordingly, using a commercially available epoxy suitable for industrial composite productions makes the developed filament suitable for many applications.
Engineering the electrospinning of MWCNTs/epoxy nanofiber scaffolds to enhance physical and mechanical properties of CFRPs
(Elsevier, 2021-09) Wable, Vidya; Biswas, Pias Kumar; Moheimani, Reza; Aliahmad, Nojan; Omole, Peter; Siegel, Amanda P.; Agarwal, Mangilal; Dalir, Hamid; Mechanical Engineering, School of Engineering and Technology
A cost-effective approach to improve the physical and mechanical properties of carbon fiber reinforced polymer (CFRP) prepreg composites, where electrospun multiwalled carbon nanotubes (MWCNTs)/epoxy nanofibers were synthesized and incorporated in between the layers of conventional CFRP prepreg composite has been presented. MWCNT-aligned epoxy nanofibers were successfully produced by an optimized electrospinning process. Nanofibers were deposited directly onto prepreg layers to achieve improved adhesion and interfacial bonding, leading to added strength and improvements in other mechanical properties. Thus, interlaminar shear strength (ILSS) and fatigue performance at high-stress regimes increased by 29% and 27%, respectively. Barely visible impact damage (BVID) energy increased significantly by up to 45%. The thermal and electrical conductivities were also enhanced significantly due to the presence of the highly conductive MWCNT networks between the CFRP layers. The presented method was capable of uniformly depositing high contents of MWCNTs at interlaminar ply interface of prepregs to strengthen/enhance CFRP properties, which has not been previously shown to be possible due to high resin viscosity caused by randomly oriented MWCNTs in epoxy system.
An evaluation of a research experience for teachers in nanotechnology
(IEEE, 2017-10) Hess, Justin L.; Chase, Anthony; Minner, Dan; Rizkalla, Maher; Agarwal, Mangilal; Mechanical Engineering, School of Engineering and Technology
This study involves the evaluation of the second implementation of a Research Experiences for Teacher Advancement In Nanotechnology (RETAIN) program offered at Indiana University-Purdue University Indianapolis (IUPUI). RETAIN represents a professional development model for providing high school teachers with laboratory research experiences in nanoscience and related content areas. In this intensive summer program, teachers spend six weeks conducting nanotechnology-related research in an IUPUI lab. As part of the RETAIN program, teachers complete six credit hours of coursework, wherein they translate their research experiences into the design of classroom modules. Teachers are expected to then implement their modules within their own classrooms during the subsequent academic year. This evaluation focuses on teachers' experiences in IUPUI labs during the summer of 2016, along with three teachers' implementation of nanotechnology labs within their courses during the 2016-2017 school year. To evaluate RETAIN, we explored teacher satisfaction, changes in teachers' content knowledge and nanotechnology perceptions, as well as changes in teachers' epistemological beliefs. Further, we explored the impact of the three teachers' module integration on their students' STEM attitudes and nanotechnology perceptions. The findings indicated that teachers were generally satisfied with the research and course experiences. Further, as a result of RETAIN participation, teachers showed increased nanotechnology content knowledge and knowledge of nanotechnology-related careers. Lastly, three teachers' integration of nanotechnology modules indicated that their students had significantly improved perceptions of nanotechnology's potential coupled with more knowledge of nanotechnology-related careers. The paper concludes with considerations of the quantitative findings in light of teachers' written reflections and author observations of teacher module integration in their classrooms.
Experimental Study of Material Removal at Nanoscale
(Elsevier, 2018-01-01) Promyoo, Rapeepan; El-Mounayri, Hazim; Agarwal, Mangilal; Mechanical Engineering, School of Engineering and Technology
In order to develop nano-machining into a viable and efficient process, there is a need to achieve a better understand the relation between process parameters (such as feed, speed, and depth of cut) and resulting geometry. In this study, a comprehensive experimental parametric study was conducted to produce a database that is used to select proper machining conditions for guiding the fabrication of precise nano-geometries. The parametric studies conducted using AFM nanosize tips showed the following: normal forces for both nano-indentation and nano-scratching increase as the depth of cut increases. The indentation depth increases with tip speed, but the depth of scratch decrease with increasing tip speed. The width and depth of scratched groove also depend on the scratch angle. The recommended scratch angle is at 90°. The surface roughness increases with step over, especially when the step over is larger than the tip radius. The depth of cut also increases as the step over decreases.
Fabrication of Submicron Thermosetting Carbon Nanotube-Epoxy Fibers Using Electrospinning
(American Society for Composites, 2020-09-20) Aliahmad, Nojan; Wable, Vidya; Biswas, Pias Kumar; Hernadez, Iran; Dalir, Hamid; Agarwal, Mangilal
Recently epoxy-based nanocomposites are gaining tremendous attention in many structural applications such as those in aerospace, automotive and motorsports. This research represents a new approach to fabricate submicron thermoset epoxy filaments enhanced with carbon nanotubes (CNT), through optimized curing followed by an electrospinning process. The optimized curing process is based on the uniform mixing of CNT with epoxy, and partial curing of the CNT/epoxy mixture with the hardener through a thermal treatment without adding any plasticizers or thermoplastic binders. Later the fibers have been made by electrospinning of the semi-cured mixture. Fig 1 shows the fabrication process of the described filaments. The key goal is to make the thermosetting epoxy without adding any thermoplastic to keep the integrity and quality of the fibers. The diameters of these filaments can be tuned between 100 nm to 500nm. Further, the CNT structure has been aligned inside the filament structure by the presence of the electrostatic field during the electrospinning process results in better stability and smaller diameters for the fibers. The fabricated filaments show that adding a low amount of CNT in the epoxy structure, better structural, electrical and thermal stability, has been achieved.
Gaussian Process Regression and Monte Carlo Simulation to Determine VOC Biomarker Concentrations Via Chemiresistive Gas Nanosensors
(IEEE Xplore, 2021-06) Rivera, Paula Angarita; Woollam, Mark; Siegel, Amanda P.; Agarwal, Mangilal; Mechanical and Energy Engineering, School of Engineering and Technology
Utilizing chemiresistive gas sensors for volatile organic compound (VOC) detection has been a growing area of investigation in the last decade. VOCs have been extensively studied as potential biomarkers for biomedical applications as they are byproducts of metabolic pathways which are dysregulated by disease. Therefore, sensor arrays have been fabricated in previous studies to detect VOC biomarkers. In the process of testing these sensors, it is highly advantageous to quantify the concentration of the VOC biomarkers with high accuracy to diagnose the disease with high sensitivity and specificity. To investigate, analyze, and understand the relation between the concentrations of the VOC to the sensor resistance response, Gaussian Process (GP) models were implemented to predict the behavior of the data with respect to the resistance when the sensor is exposed to a range of concentrations of VOCs. Additionally, the relation between the concentration and resistance of the sensor was studied to predict the concentration of the VOC when a resistance is obtained. Monte Carlo Simulation Sampling from the GP model was utilized to generate data to further understand the trend. The results demonstrated that the relation between the concentration and resistance is linear. The model was tested with sampling data and its accuracy was evaluated.

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