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 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 Resin Transfer Molding(Center for Composite Materials, 2004-03) Center for Composite MaterialsThe Liquid Composite Molding (LCM) refers to a number of processes that use liquid resin to impregnate the stationary fibrous pre-form. The variation of this process that is of a particular interest is Resin Transfer Molding (RTM). During the RTM Process, the preform is placed into the mold cavity, the mold is closed and the resin is inject-ed into the cavity under pressure.Item Liquid Molding Innovation: Membrane-Based RTM and VIP Processing(Center for Composite Materials, 2004-03) Center for Composite MaterialsItem Time-Domain Reflectometry: Novel Sensors for Process Sensing and Control(Center for Composite Materials, 2004-03) Center for Composite MaterialsItem SMARTMolding(Center for Composite Materials, 2004-03) Center for Composite MaterialsItem 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 Composite Design Software(Center for Composite Materials, 2008) Center for Composite MaterialsItem Peptide hydrogels – versatile matrices for 3D cell culture in cancer medicine(Frontiers Media S.A., 2015-04-20) Worthington, Peter; Pochan, Darrin J.; Langhans, Sigrid A.; PeterWorthington, Darrin J. Pochan and Sigrid A. Langhans; Worthington, Peter; Pochan, Darrin J.Traditional two-dimensional (2D) cell culture systems have contributed tremendously to our understanding of cancer biology but have significant limitations in mimicking in vivo conditions such as the tumor microenvironment. In vitro, three-dimensional (3D) cell culture models represent a more accurate, intermediate platform between simplified 2D culture models and complex and expensive in vivo models. 3D in vitro models can overcome 2D in vitro limitations caused by the oversupply of nutrients, and unphysiological cell–cell and cell–material interactions, and allow for dynamic interactions between cells, stroma, and extracellular matrix. In addition, 3D cultures allowfor the development of concentration gradients, including oxygen, metabolites, and growth factors, with chemical gradients playing an integral role in many cellular functions ranging from development to signaling in normal epithelia and cancer environments in vivo. Currently, the most common matrices used for 3D culture are biologically derived materials such as matrigel and collagen. However, in recent years, more defined, synthetic materials have become available as scaffolds for 3D culture with the advantage of forming well-defined, designed, tunable materials to control matrix charge, stiffness, porosity, nanostructure, degradability, and adhesion properties, in addition to other material and biological properties. One important area of synthetic materials currently available for 3D cell culture is short sequence, self-assembling peptide hydrogels. In addition to the review of recent work toward the control of material, structure, and mechanical properties, we will also discuss the biochemical functionalization of peptide hydrogels and how this functionalization, coupled with desired hydrogel material characteristics, affects tumor cell behavior in 3D culture.Item Processing and Characterization of a Novel Distributed Strain Sensor Using Carbon Nanotube-Based Nonwoven Composites(MDPI AG, 2015-07-21) Dai, Hongbo; Thostenson, Erik T.; Schumacher, Thomas; Hongbo Dai, Erik T. Thostenson, and Thomas Schumacher; Dai, Hongbo; Thostenson, Erik T.; Schumacher, ThomasThis paper describes the development of an innovative carbon nanotube-based non-woven composite sensor that can be tailored for strain sensing properties and potentially offers a reliable and cost-effective sensing option for structural health monitoring (SHM). This novel strain sensor is fabricated using a readily scalable process of coating Carbon nanotubes (CNT) onto a nonwoven carrier fabric to form an electrically-isotropic conductive network. Epoxy is then infused into the CNT-modified fabric to form a free-standing nanocomposite strain sensor. By measuring the changes in the electrical properties of the sensing composite the deformation can be measured in real-time. The sensors are repeatable and linear up to 0.4% strain. Highest elastic strain gage factors of 1.9 and 4.0 have been achieved in the longitudinal and transverse direction, respectively. Although the longitudinal gage factor of the newly formed nanocomposite sensor is close to some metallic foil strain gages, the proposed sensing methodology offers spatial coverage, manufacturing customizability, distributed sensing capability as well as transverse sensitivity.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 Recent Advances in Modeling and Experiments of Kevlar Ballistic Fibrils, Fibers, Yarns and Flexible Woven Textile Fabrics – A Review(Sage Publications, 2016-05-02) Sockalingam, Subramani; Chowdhury, Sanjib C.; Gillespie, John W. Jr.; Keefe, Michael; Subramani Sockalingam, Sanjib C. Chowdhury, John W. Gillespie Jr and Michael Keefe; Sockalingam, Subramani; Chowdhury, Sanjib C.; Gillespie, John W. Jr.; Keefe, MichaelBallistic impact onto flexible woven textile fabrics is a complicated multi-scale problem given the structural hierarchy of the materials, anisotropic material behavior, projectile geometry-fabric interactions, impact velocity and boundary conditions. Although this subject has been an active area of research for decades, the fundamental mechanisms such as material failure, dynamic response, multi-axial loading occurring at the lower length scales during impact are not well understood. This paper reviews the recent advances in modeling and experiments of Kevlar ballistic fibrils, fibers, yarns and flexible woven textile fabrics pertinent to the deformation modes occurring during impact and serves to identify topics worthy of further investigation that will advance the basic understanding of the phenomena governing transverse impact. This review also explores on aspects such as homogeneous versus heterogeneous behavior of yarns consisting of individual fibers and the inelastic transverse behavior of the fiber which is not considered in the previous review papers on this topic.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 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 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 Composite Design & Analysis Capabilities(Center for Composite Materials, 2018-09) Center for Composite MaterialsItem Additive manufacturing(Center for Composite Materials, 2018-09) Center for Composite MaterialsItem 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.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 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.