Center for Composite Materials
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The Center for Composite Materials(CCM) is an internationally recognized, interdisciplinary center of excellence for composites education and research. The Center was founded in 1974 and is in the College of Engineering at the University of Delaware.
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Item 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 RashefThis 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.Item Additive manufacturing(Center for Composite Materials, 2018-09) Center for Composite MaterialsItem Adhesion Characterization and Enhancement between Polyimide-Silica Composite and Nodulated Copper for Applications in Next-Generation Microelectronics(ACS Applied Materials & Interfaces, 2024-01-17) Doshi, Sagar M.; Barry, Alexander; Schneider, Alexander; Parambil, Nithin; Mulzer, Catherine; Yahyazadehfar, Mobin; Samadi-Dooki, Aref; Foltz, Benjamin; Warrington, Keith; Wessel, Richard; Zhang, Lei; Simone, Christopher; Blackman, Gregory S.; Lamontia, Mark A.; Gillespie, John W. Jr.As the need for high-speed electronics continues to rise rapidly, printed wiring board (PWB) requirements become ever-more demanding. A typical PWB is fabricated by bonding dielectric films such as polyimide to electrically conductive copper foil such as rolled annealed (RA) copper and is expected to become thinner, flexible, durable, and compatible with high-frequency 5G performance. Polyimide films inherently feature a higher coefficient of thermal expansion (CTE) than copper foils; this mismatch causes residual thermal stresses. To attenuate the mismatch, silica nanoparticles may be used to reduce the CTE of PI. A nodulated copper surface can be used to enhance the Cu/PI adhesion by additional bonding mechanisms that could include a type of mechanical bonding, which is a focus of this study. In this investigation, a 90° peel test was used to measure the peel strength in copper/polyimide/copper laminates containing nodulated copper and polyimide reinforced with 0, 20, and 40 wt % silica nanoparticles. The influence of silica nanoparticles on the peel strength was quantitatively evaluated. Laminates incorporating polyimide films lacking silica nanoparticles had a ∼3.75× higher peel strength compared with laminates reinforced with 40% silica. Their failure surfaces were analyzed by using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy to identify the mode of failure and to understand bonding mechanisms. The key bonding mechanism, mechanical interlocking, was achieved when the polyimide surrounded or engulfed the copper nodules when the laminate was created. Post-testing failure surface analysis revealed the presence of copper on the polyimide side and polyimide on the copper side, indicating mixed mode failure. An analytical model was developed to determine the impact of applied pressure, temperature, and time on the polyimide penetration and mechanical interlocking around the copper nodules. The model was validated by measuring the peel strength on another set of specimens fabricated using increased temperature and pressure that showed a 3× increase in peel strength compared to lower temperature/pressure processing conditions. This enhanced adhesion resulted from the lower polymer material viscosity at higher temperatures, which fosters deeper and more complete penetration around the copper nodules during processing at higher pressures for longer durations. The methodology of combining peel testing, viscosity and CTE measurement, SEM/EDX, surface chemical analysis, and penetration depth calculation developed herein enables the calculation of the desired processing parameters to enhance functionality and improve adhesion.Item Annulus Void Fill Material for Rehabilitated Sliplined Culverts(The University of Akron, 2023-03) Patnaik, Anil; Alzlfawi, Abdullah; Das, ShagataSliplining 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.Item 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.Item 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 KelvinNanocomposites 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.Item Complex Shaped Mold Manufacturing by Means of Laminate Object Manufacturing(Center for Composite Materials, 2003) Marais, JoachimComplex shaped composite parts are needed for many applications. The base of every complex shaped part is a mold that represents the shape. However, the fabrication of a mold is very expensive and requires a high amount of skills, money and labor time. Therefore, a low cost, flexible and fast process is needed. Rapid prototyping processes such as Laminate Object Manufacturing (LOM) can reduce cost and time. But is this process, based on sensitive paper, can be used to build molds? The goal of this project is to evaluate the manufacturing process of a paper baser LOM mold and to improve the strength of such a mold in order to increase its durability.Item Composite Design & Analysis Capabilities(Center for Composite Materials, 2018-09) Center for Composite MaterialsItem Composite Design Software(Center for Composite Materials, 2008) Center for Composite MaterialsItem 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, SrikanthTransportation 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.Item 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, JovanThis 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.Item 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.Item 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.Item Experimental characterization of tensile properties of epoxy resin by using micro-fiber specimens(Sage Publications, 2016-09-21) Misumi, Jun; Ganesh, Raja; Sockalingam, Subramani; Gillespie, John W. Jr.; Jun Misumi, Raja Ganesh, Subramani Sockalingam, John W Gillespie; Misumi, Jun; Ganesh, Raja; Sockalingam, Subramani; Gillespie, John W. JrIn unidirectional carbon fiber-reinforced plastic laminates, the distance between fibers can varies 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 µm 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 µm 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 is 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 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.Item 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.Item 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.Item 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.Item An Introduction to the Center for Composite Materials(Center for Composite Materials, 2004-03) Center for Composite MaterialsItem Liquid Injection Molding Simulation(Center for Composite Materials, 2004-03) Center for Composite MaterialsItem Liquid Molding Innovation: Membrane-Based RTM and VIP Processing(Center for Composite Materials, 2004-03) Center for Composite Materials