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Open access publications by faculty, staff, postdocs, and graduate students from the Center for Composite Materials.

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    Design optimization of a multi-material, fiber-reinforced composite-intensive body-in-white of a mid-size SUV
    (CAMX 2023 Conference Proceedings, 2023-10-30) Deshpande, Amit M.; Sadiwala, Rushabh; Brown, Nathan; Lavertu, Pierre-Yves; Pradeep, Sai Aditya; Headings, Leon M.; Zhao, Ningxiner; Losey, Brad; Hahnlen, Ryan; Dapino, Marcelo J.; Li, Gang; Pilla, Srikanth
    Transportation accounts for almost a third of all energy consumption and emissions in the U.S. With an emphasis on improving the energy efficiency of vehicles and transitioning to electrified vehicles, lightweighting has become relevant to compensate for the added complexity of battery packs and hybrid powertrains. Lightweight materials such as aluminum, magnesium, and fiber-reinforced plastic (FRP) composites can reduce the vehicle’s structural mass, the body-in-white (BIW), by up to 50%. However, the higher proportion of large sports utility vehicles (SUVs) and trucks in the North American fleet poses a challenge, as the larger size and high production scale of the structural components for this segment can significantly increase material costs. Thus, a multi-material approach to deploy FRP composites at select locations in an existing metal BIW can help advance composites design, integration, and manufacturing technologies. Furthermore, these designs can be translated for future EV structures. This study utilizes a systems approach to 1) establish design targets through structural analysis of the baseline SUV BIW design under various static and dynamic load cases, 2) conceptualize multi-material designs, and 3) assess the designs to meet lightweighting, cost, and sustainability objectives. Sustainable recycled carbon fiber-reinforced composites and other cost-effective FRP composite materials manufactured using state-of-the-art high-pressure resin transfer molding (HP RTM) technology were assessed for use in structural elements. An ultrasonic additive manufacturing (UAM) technique was implemented to produce mechanically interlocked metal-fiber transition joints to serve as a joining mechanism between fibers and metals in the multi-material design. To incorporate the transition joint design into the topology optimization scheme, a high-fidelity model of the fiber-metal transition joints that describes the fiber-oriented interactions between the fibers, cured-epoxy matrix, and metal components was developed. This model's results accurately represented the behavior from experimental testing. They can be transferred to the FEA solver as a computationally efficient material card specifically for use at the metal-composite transition regions in the proposed designs. The results from this system-level multi-material composites integration study have been presented.
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    Annulus Void Fill Material for Rehabilitated Sliplined Culverts
    (The University of Akron, 2023-03) Patnaik, Anil; Alzlfawi, Abdullah; Das, Shagata
    Sliplining is a method used by transportation agencies to rehabilitate deteriorated culverts. In recent years, ODOT discovered a number of sliplined culverts that did not have their annulus void spaces completely filled. Such culverts experience distortion and settlement as well as reduced structural capacity. Field inspections of several sliplined culverts in Ohio in this study confirmed that the lack of complete annulus void filling is a prevalent problem. Filler grout properties, particularly poor flow characteristics, would prevent the grout from completely filling annulus voids. This led to the investigation of grout properties that are most important to achieve good flow and fillability. New mixture proportions of a controlled low-strength material (CLSM) and cellular grout C40 were developed based on extensive laboratory testing. These improved grouts were also mixed in a batching plant at a larger scale and were pumped over a 200-ft length at an upslope of 2.5% to determine the suitability of these grouts in practical applications. Grouting of the annulus voids of 20-foot-long sections was verified using a 36-inch liner pipe sliplined within a 48-inch host pipe. A suggested basis for changes to the relevant ODOT specifications in SS 837 is recommended.
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    Development of a Recyclable Flax Fiber Reinforced Polymer Composite
    (Composites in Civil Engineering, 2023-06-28) Das, Shagata; Doshi, Sagar; Millan, Emmanuel; Mendez, Damaris; Luckenbill, Dan; Tatar, Jovan
    This study compared the mechanical properties of a recyclable flax fiber reinforced polymer composite (FFRP) with a covalent adaptable network (CAN) matrix to an FFRP composite with a conventional (unrecyclable) epoxy resin matrix. The results indicated that composites fabricated via vacuum-assisted resin transfer molding (VARTM) exhibited up to 19% higher tensile modulus and strength compared to those fabricated via hand layup, attributed to reduced air void content and more uniform fiber alignment. Microscopy evidence supported by mechanical property tests revealed superior adhesion of the CAN matrix to flax fibers compared to conventional epoxy resin. Additionally, a solvent-based method was demonstrated for separating fibers from the CAN matrix, facilitating reuse or upcycling.
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    Multi-axis Manufacture of Conformal Metasurface Antennas
    (IEEE Antennas and Wireless Propagation Letters, 2023-06-09) Gupta, Ellen; Bonner, Colin; Lazarus, Nathan; Mirotznik, Mark S.; Nicholson, Kelvin J.
    A conformal metasurface antenna exhibiting a pencil beam radiation pattern at 10.0 GHz has been designed using the Voronoi partition approach, and fabricated on the Kahu Uninhabited Aerial System (UAS) fuselage. Two manufacturing methods are presented and compared. The first approach utilized a 3-axis Trotec fiber laser to etch the flattened metasurface geometry in copper foil. The etched pattern was then ‘stretched’ over the UAS geometry. The second approach utilized a 6-axis nScrypt (retrofitted with an IDS aerosol jetting tool) to conformally print the metasurface pattern directly on the UAS fuselage. An electroless copper plating step was then utilized to improve the radiofrequency (RF) conductivity of the printed silver. Both manufacturing methods yielded functional metasurface antennas with equivalent performance at the operating frequency. However, the first method is limited to geometries that can be ‘flattened’ with acceptable tolerances, whereas the second approach is amenable to all practical geometries. This demonstration of two manufacturing techniques is a critical step forward in the cost-effective deployment of truly conformal metasurface antennas on realistic geometries.
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    Carbon Additive Manufacturing with a Near-Replica “Green-to-Brown” Transformation
    (Advanced Materials, 2023-05-30) Zhang, Chunyan; Shi, Baohui; He, Jinlong; Zhou, Lyu; Park, Soyeon; Doshi, Sagar; Shang, Yuanyuan; Deng, Kaiyue; Giordano, Marc; Qi, Xiangjun; Cui, Shuang; Liu, Ling; Ni, Chaoying; Fu, Kun Kelvin
    Nanocomposites containing nanoscale materials offer exciting opportunities to encode nanoscale features into macroscale dimensions, which produces unprecedented impact in material design and application. However, conventional methods cannot process nanocomposites with a high particle loading, as well as nanocomposites with the ability to be tailored at multiple scales. A composite architected mesoscale process strategy that brings particle loading nanoscale materials combined with multiscale features including nanoscale manipulation, mesoscale architecture, and macroscale formation to create spatially programmed nanocomposites with high particle loading and multiscale tailorability is reported. The process features a low-shrinking (<10%) “green-to-brown” transformation, making a near-geometric replica of the 3D design to produce a “brown” part with full nanomaterials to allow further matrix infill. This demonstration includes additively manufactured carbon nanocomposites containing carbon nanotubes (CNTs) and thermoset epoxy, leading to multiscale CNTs tailorability, performance improvement, and 3D complex geometry feasibility. The process can produce nanomaterial-assembled architectures with 3D geometry and multiscale features and can incorporate a wide range of matrix materials, such as polymers, metals, and ceramics, to fabricate nanocomposites for new device structures and applications.
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    Extrusion-Based Additively Manufactured PAEK and PAEK/CF Polymer Composites Performance: Role of Process Parameters on Strength, Toughness and Deflection at Failure
    (Journal of Composites Science, 2023-04-11) Sharafi, S.; Santare, M. H.; Gerdes, J.; Advani, S. G.
    Poly aryl-ether-ketone (PAEK) belongs to a family of high-performance semicrystalline polymers exhibiting outstanding material properties at high temperatures, making them suitable candidates for metallic part replacement in different industries such as aviation, oil and gas, chemical, and biomedical. Fused filament fabrication is an additive manufacturing (AM) method that can be used to produce intricate PAEK and PAEK composite parts and to tailor their mechanical properties such as stiffness, strength and deflection at failure. In this work, we present a methodology to identify the layer design and process parameters that will have the highest potential to affect the mechanical properties of additively manufactured parts, using our previously developed multiscale modeling framework. Five samples for each of the ten identified process conditions were fabricated using a Roboze-Argo 500 version 2 with heated chamber and dual extruder nozzle. The manufactured PAEK and PAEK/carbon fiber samples were tested until failure in an Instron, using a video extensometer system. Each sample was prepared with a speckle pattern for post analysis using digital image correlation (DIC) to measure the strain and displacement over its entire surface. The raster angle and the presence of fibers had the largest influence on the mechanical properties of the AM manufactured parts, and the resulting properties were comparable to the mechanical properties of injection molded parts.
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    Mechanical behavior of UV-cured composite stepped lap adhesive joints
    (SAMPE Conference Proceedings 2023, 2023-04-18) Das, Shagata; Gillespie, John W. Jr.; Shenton, Harry W. III; Tatar, Jovan
    Joints often control the design of composite structures because they represent locations of high stress concentrations. Adhesive joints offer several benefits over mechanically fastened connections such as reduced stress concentrations, and higher joint efficiency. This study evaluates the performance of stepped lap adhesive joints. The novelty lies in the implementation of UV-cured vinyl ester resin which allows integration of co-cured stepped lap joints in applications where fast curing at ambient temperatures is required. The experimental program consisted of a series of tensile tests on 20-ply 7781 E-glass laminates integrating UV-cured stepped lap joints, where the primary variables were stepped lap joint angle (ranging from 0.9° to 5.7°) and number of ply drops (ranging from 1 to 10). Physical properties of all the UV-cured joint panels, such as density, void content, fiber volume fraction, and hardness, were also evaluated and compared between the test groups. The preliminary findings indicate that reducing the scarf angle from 5.7° to 0.9° increased the joint strength by a maximum of 115%. The joint strength efficiency approached 100% of the laminate tensile strength for 19-step joints having a scarf angle of 0.9º.
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    Bladder expandable robotic system and UV materials for rapid internal pipeline repair
    (SAMPE Conference Proceedings 2023, 2023-04-18) Tierney, John J.; Vanarelli, Alex; Fuessel, Lukas; Abu-Obaid, Ahmad; Sauerbrunn, Steve; Das, Shagata; Deitzel, Joseph; Tatar, Jovan; Heider, Dirk; Shenton, Harry W. III; Kloxin, Christopher J.; Sung, Dae Han; Thostenson, Erik; Gillespie, John W. Jr.
    This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines—with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year service life by addressing the unique loading conditions of the pipe repair allowing for the design customization of the preforms to accommodate the state of pipe corrosion, access points or other local features that may vary along the length of the pipe. The approach offers maximum design flexibility and customization while minimizing installation time and cost. The preforms are fabricated above ground using rapid automated manufacturing methods for quality control. The preforms are transported by a tethering system to the robot. The robot is comprised of a self-propelled dual inflation expandable bladder system that places, consolidates, and cures standard or custom composite sections along the entire pipe length in a continuous co-cure process. This system is designed to adapt to pipe features that include lateral tees, service connections, joints, gaps, and irregular cross sections. In addition, variable thickness composite sections can be placed along the pipe where exposed to high external loads under railroads, highways, airports or where soil erosion and movement occurs. This paper presents the robot design, assessment of UV curable resins, embedded sensing methods, and fabrication of pipe sections with this system.
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    Efficient numerical modeling of liquid infusion into a porous medium partitioned by impermeable perforated interlayers
    (International Journal for Numerical Methods in Engineering, 2022-11-02) Moretti, Laure; Simacek, Pavel; Advani, Suresh G.
    Numerical modeling of flow through porous media and the simulation of liquid flow through orifices, channels and perforated walls, membranes, interlayers find applications in various fields. However, the mesh refinement needed to describe the detail at the scale of orifices within a domain multiple orders of magnitude larger raises numerical challenges. The present work proposes a pragmatic solution to model perforated layers partitioning a large porous media domain using 1D elements to model the holes and connect the 3D elements which represent the porous media. As an illustration, the approach is applied in liquid composite molding processes, and to the processing of large thick panels toughened with perforated interlayers. However, this work could be adopted in numerous fields. The combination of 3D and 1D elements to manage components with different dimensions has been used before, however no proper analysis of the loss of accuracy introduced has been conducted to our knowledge. A systematic parametric study is conducted to quantify the impact of the length of the domain, the number of interlayers, the diameter of the holes and the viscosity of the fluid on the loss of accuracy. Meshing rules and directions are provided to improve the accuracy of the simulations.
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    A High-Consolidation Electron Beam-Curing Process for Manufacturing Three-Dimensional Advanced Thermoset Composites
    (Journal of Manufacturing Science and Engineering, 2022-07-27) Rizzolo, Robert H.; Walczyk, Daniel F.; Montoney, Daniel; Simacek, Pavel; Mahbub, Md Rashef
    This paper describes the application of a new manufacturing process for low-cost and rapid consolidation and curing of advanced thermoset composites that avoids the use of expensive prepreg, autoclaving, and thermally induced curing. The process, called VIPE, uses a novel tooling design that combines vacuum infusion (VI) of a dry preform with resin, a rigidly backed pressure focusing layer (P) made of an elastomer to consolidate the wet preform with uniform pressure, and high-energy electron beam curing (E). A VIPE tool is engineered and fabricated to manufacture 3D laminate bicycle seats composed of woven carbon fiber textile and an electron beam-curable epoxy acrylate. Details of the tooling design discussed include computational fluid dynamics (CFD) simulation of the vacuum infusion, iterative structural finite element analysis (FEA) to synthesize the pressure focusing layer (PFL), structural FEA to design the top mold made of a composite sandwich structure for electron beam transparency, and Monte Carlo electron absorption simulations to specify the e-beam energy level. Ten parts are fabricated using the matched tool (bottom aluminum mold covered with silicone layer and top mold with carbon/epoxy skins separated by foam core) after the dry textile preform contained within is infused with resin, the tool halves are clamped under load, and a 3.0 MeV e-beam machine bombards the tool for less than 1 min. Part thickness, part stiffness, surface roughness, and fiber and void volume fractions measurements show that aerospace quality parts with low cycle times are achievable, although there is high variability due to the small number of replicates and need for process optimization.
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    Theory-guided machine learning for optimal autoclave co-curing of sandwich composite structures
    (Polymer Composites, 2022-07-06) Lavaggi, Tania; Samizadeh, Mina; Niknafs Kermani, Navid; Khalili, Mohammad Mahdi; Advani, Suresh G.
    The bonding of a honeycomb core to the thermoset prepreg facesheets by co-curing them allows one to manufacture composite sandwich structures in a single operation. However, the process is strongly dependent on the prescribed autoclave cure cycle. A previously developed physics-based simulation can predict the bond quality as a function of the process parameters. The disadvantage of physics-based simulations is the high computational effort needed to identify the optimal cure cycle to fabricate sandwich structures with desired bond-line properties. Theory guided machine learning (TGML) methods have demonstrated their capabilities to reduce the computational effort for different applications. In this work, three TGML models are trained on a data set produced from physics-based simulations to predict the co-cure process of honeycomb sandwich structures. The accuracy of the TGML models were compared to select the best performing predictive tool. In addition to reduction of computational time by orders of magnitude, we demonstrate how the TGML tools can also quantify the contribution of each process parameter on the properties of the fabricated part. The most accurate model was implemented in an optimization routine to tune the input process parameters to obtain the desired properties such as the bond-line porosity and facesheet consolidation level. This methodology could be extended to any process simulation of composites manufacturing processes.
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    Experimental characterization of tensile properties of epoxy resin by using micro-fiber specimens
    (SAGE Publications, 2016) Misumi, Jun; Ganesh, Raja; Sockalingam, Subramani; Gillespie, John W. Jr.; Jun Misumi, Raja Ganesh, Subramani Sockalingam and John W Gillespie Jr.; Misumi, Jun; Ganesh, Raja; Sockalingam, Subramani; Gillespie, John W. Jr.
    In unidirectional carbon fiber reinforced plastic (CFRP) laminates, the distance between fibers can vary from submicron to micron length scales. The mechanical properties of the matrix at this length scale are not well understood. In this study, processing methods have been developed to produce high quality epoxy micro-fibers with diameters ranging from 100 to 150 um that are used for tensile testing. Five types of epoxy resin systems ranging from standard DGEBA to high-crosslink TGDDM and TGMAP epoxy systems have been characterized. Epoxy macroscopic specimens with film thickness of 3300 um exhibited brittle behavior (1.7 to 4.9% average failure strain) with DGEBA resin having the highest failure strain level. The epoxy micro-fiber specimens exhibited significant ductile behavior (20 to 42% average failure strain) with a distinct yield point being observed in all five resin systems. In addition, the ultimate stress of the highly cross-linked TGDDM epoxy fiber exceeded the bulk film properties by a factor of two and the energy absorption was over 50 times greater on average. The mechanism explaining the dramatic difference in properties are discussed and is based on size effects (the film volume is about 2000 times greater than the fiber volume within the gage sections) and surface defects. Based on the findings 3 presented in this paper, the microscale fiber test specimens are recommended and provide more realistic stress-strain response for describing the role of the matrix in composites at smaller length scales.
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    Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process
    (Journal of Visualized Experiments (JoVE), 2017-05-30) Yeo, Eudora S. Y.; Mathys, Gary I.; Brack, Narelle; Thostenson, Erik T.; Rider, Andrew N.; Eudora S. Y. Yeo, Gary I. Mathys, Narelle Brack, Erik T. Thostenson, Andrew N. Rider; Thostenson, Erik T.
    Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the as-received form, carbon nanomaterials, such as carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), may contain large agglomerates. Both agglomerates and impurities will diminish the benefits of the unique electrical and mechanical properties offered when CNTs or GNPs are incorporated into polymers or composite material systems. Whilst a variety of methods exist to functionalize carbon nanomaterials and to create stable dispersions, many the processes use harsh chemicals, organic solvents, or surfactants, which are environmentally unfriendly and may increase the processing burden when isolating the nanomaterials for subsequent use. The current research details the use of an alternative, environmentally friendly technique for functionalizing CNTs and GNPs. It produces stable, aqueous dispersions free of harmful chemicals. Both CNTs and GNPs can be added to water at concentrations up to 5 g/L and can be recirculated through a high-powered ultrasonic cell. The simultaneous injection of ozone into the cell progressively oxidizes the carbon nanomaterials, and the combined ultrasonication breaks down agglomerates and immediately exposes fresh material for functionalization. The prepared dispersions are ideally suited for the deposition of thin films onto solid substrates using electrophoretic deposition (EPD). CNTs and GNPs from the aqueous dispersions can be readily used to coat carbon- and glass-reinforcing fibers using EPD for the preparation of hierarchical composite materials.
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    Dynamic effects of single fiber break in unidirectional glass fiber-reinforced composites
    (Sage Publications, 2016-09-15) Ganesh, Raja; Sockalingam, Subramani; Haque, Bazle Z. (Gama); Gillespie, John W. Jr.; Raja Ganesh, Subramani Sockalingam, Bazle Z. (Gama) Haque and John W. Gillespie, Jr.; Ganesh, Raja; Sockalingam, Subramani; Haque, Bazle Z. (Gama); Gillespie, John W. Jr.
    In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process which leads to stress concentrations in the interface, matrix and neighboring fibers that can propagate at high speed over long distances. To gain better understanding of this event, a fiber-level finite element model of a 2-dimensional array of S2-glass fibers embedded in an elastic epoxy matrix with interfacial cohesive traction law is developed. The brittle fiber fracture results in release of stored strain energy as a compressive stress wave that propagates along the length of the broken fiber at speeds approaching the axial wave-speed in the fiber (6 km/s). This wave induces an axial tensile wave with a dynamic tensile stress concentration in adjacent fibers that diminishes with distance. Moreover, dynamic interfacial failure is predicted where debonding initiates, propagates and arrests at longer distances than predicted by models that assume quasi-static fiber breakage. In the case of higher strength fibers breaks, unstable debond growth is predicted. A stability criterion to define the threshold fiber break strength is derived based on an energy balance between the release of fiber elastic energy and energy absorption associated with interfacial debonding. A contour map of peak dynamic stress concentrations is generated at various break stresses to quantify the zone-of-influence of dynamic failure. The dynamic results are shown to envelop a much larger volume of the microstructure than the quasi-static results. The implications of dynamic fiber fracture on damage evolution in the composite are discussed.
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