Green and durable engineered cementitious composites (GD-ECC) with recycled PE fiber, desert sand, and carbonation curing: Mixture design, durability performance, and life-cycle analysis
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Construction & Building Technology↗
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The Impact of Carbonation Curing on the Fatigue Behavior of Polyvinyl Alcohol Engineered Cementitious Composites (PVA-ECC)
Use of Engineered Cementitious Composites (ECC) has been proven to enhance structural fatigue resistance and reduce the use-phase emissions for transportation infrastructure. Carbonation curing offers an opportunity to reduce the embodied carbon of ECC via direct CO 2 sequestration. In this study, the impact of carbonation curing on ECC’s fatigue resistance was examined. ECC’s CO 2 uptake, static flexural behavior, flexural fatigue performance, and single fiber pull-out behavior were studied experimentally. Midspan deflection up to 3 million cycles under fatigue load, fatigue stress-life relationship, and failure mechanism for carbonation-cured and air-cured ECC were investigated. Carbonation curing was found to significantly improved the fatigue life of ECC and lowered the midspan deflection under the same stress. Further, CO 2 -cured ECC can achieve >20% CO 2 uptake per cement mass after 24-hour carbonation curing. Carbonation curing increased ECC’s flexural strength by 32% and promoted crack width control capability, with maximum post-fatigue crack width reduced from 148 μm to 76 μm. As a result, the positive impact of carbonation curing on the fatigue behavior of ECC simultaneously lowers the embodied and operational carbon of ECC structural members subjected to fatigue loading during service.
36 MATERIALS SCIENCE↗
Development of sustainable low carbon Engineered Cementitious Composites with waste polyethylene fiber, sisal fiber and carbonation curing
Engineered cementitious composites (ECC) is an advanced fiber-reinforced cementitious composite with high tensile ductility. However, the binder and fiber system in ECC incur high economic and environmental cost. In this study, a low carbon ECC was developed by substituting virgin polyethylene fiber with waste polyethylene fiber (WPE) from waste marine fishing nets. Carbonation curing was applied to further reduce embodied carbon footprint via direct CO 2 mineralization. This research examined the low carbon ECC’s mechanical properties, including compressive strength and tensile strength and ductility. The CO 2 footprint and material costs of ECC were also investigated. The objective was to develop an ECC competitive to normal concrete economically and environmentally while maintain the unique ductile performance of ECC. Results suggest that carbonation-cured WPE reinforced ECC possesses 50% of the CO 2 footprint and 37% of the cost of traditional concrete. Meanwhile, this low carbon ECC maintains at least 4 MPa tensile strength and 6% tensile ductility. This research demonstrates the feasibility of developing construction materials with low environmental impact while maintaining high performance for civil infrastructure applications. As a result, the adoption of WPE in ECC provides a plausible pathway to recycle marine waste into the construction industry that urgently needs to be decarbonized.
42 ENGINEERING↗
Life cycle assessment of railway ties fabricated with ductile cementitious composites and carbonation curing
This paper evaluates the lifecycle economic and environmental benefits of implementing CO 2 utilization and storage within advanced engineered cementitious composite (ECC) railway ties. Using CO 2 -treated ECC ties can yield lifecycle benefits primarily due to enhanced material properties – increased lifespan in this case – instead of due to the stored CO 2 that would otherwise enter the atmosphere. Sequestration-based policies such as 45Q in the United States would therefore not incentivize deployment of ECC railway ties, despite their considerable CO 2 avoidance opportunities. To reach these conclusions, cradle-to-grave lifecycle models were developed for ECC ties and conventional concrete ties and evaluated under 1000 possible use-phase scenarios. The models incorporated premature tie failures – consistent with real-world observations – that were used to study a wide range of non-linear impacts arising from the random nature of tie failures and replacements. The results show that past studies that neglected premature failure of ties may have underestimated lifecycle greenhouse gas (GHG) emissions of concrete rail ties by nearly three times. Overall, servicing a track with ECC ties instead of concrete ties can reduce the lifecycle costs and GHG emissions by 12% and 21% respectively, based on median values of 1000 model run results. The expected benefits would be larger for entities like Amtrak that plan to expand concrete tie infrastructure despite significant challenges with premature concrete tie failures. Furthermore, the results of this study suggest that the lifespan of ECC ties needs to be at least 25% longer than concrete ties to achieve net lifecycle benefits. The possibility of this should be tested and confirmed under real-world conditions.
42 ENGINEERING↗
Analysis of cured carbon-phenolic decomposition products to investigate the thermal decomposition of nozzle materials
The development of a mass spectrometer/thermal analyzer/computer (MS/TA/Computer) system capable of providing simultaneous thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and evolved gas detection and analysis (EGD and EGA) under both atmospheric and high pressure conditions is described. The combined system was used to study the thermal decomposition of the nozzle material that constitutes the throat of the solid rocket boosters (SRB).
Thompson, James M.↗
Amino acids as performance-controlling additives in carbonation-activated cementitious materials
This article presents an investigation on the application of amino acids to control the CaCO{sub 3} crystallization in carbonation cured wollastonite composites. It was observed that wollastonite carbonated without any amino acid formed calcite as the primary polymorph of CaCO{sub 3}. In contrast, the use of amino acids as admixtures resulted in the formation of stable amorphous calcium carbonate (ACC), vaterite, and aragonite during the carbonation of wollastonite. The carbonated composites produced with amino acids were observed to have a lower critical pore size, but a higher total porosity, compared to the control batch. Additionally, the utilization of amino acids was observed to increase the flexural strength and compressive strength of the composites up to 106% and 48%, respectively, compared to the control batch. Such performance enhancement of the carbonated composites in the presence of amino acids was attributed to the reduced critical pore size and the formation of organic-inorganic hybrid phases in the matrix.
36 MATERIALS SCIENCE↗
Composition and Process for Retarding the Premature Aging of PMR Monomer Solutions and PMR Prepegs
Polyimides are derived from solutions of at least one low-boiling organic solvent, e.g. isopropanol containing a mixture of polyimide-forming monomers. The monomeric solutions have an extended shelf life at ambient (room) temperatures as high as 80 C, and consist essentially of a mixture of monoalkyl ester-acids, alkyl diester-diacids and aromatic polyamines wherein the alkyl radicals of the esteracids are derived from lower molecular weight aliphatic secondary alcohols having 3 to 5 carbon atoms per molecule such as isopropanol, secondary butanol, 2-methyl-3-butanol, 2 pentanol or 3-pentanol. The solutions of the polyimide-forming monomers have a substantially improved shelf-life and are particularly useful in the aerospace and aeronautical industry for the preparation of polyimide reinforced fiber composites such as the polyimide cured carbon composites used in jet engines, missiles, and for other high temperature applications.
Alston, William B.↗
Induction graphitizing furnace acceptance test report
The induction furnace was designed to provide the controlled temperature and environment required for the post-cure, carbonization and graphitization processes for the fabrication of a fibrous graphite NERVA nozzle extension. The acceptance testing required six tests and a total operating time of 298 hrs. Low temperature mode operations, 120 to 850 C, were completed in one test run. High temperature mode operations, 120 to 2750 C, were completed during five tests.
Source record↗
Evaluation of Temperature Gradients During Cure of a Thick Carbon Fiber/Epoxy Composite
The purpose of this study is to evaluate the development of thermal gradients throughout thick (1") carbon fiber composites and determine the effect of internal temperature distribution during cure on the observed mechanical properties in those composites. Composites up to 1.5" thick (56 plies) were fabricated with T700S/TC380 braided prepreg from Tencate following a modified vacuum bag layup procedure to include embedded thermocouples within the plies of the composite. Composite panels were cured in a programmable oven with thermocouple reading embedded throughout the panel thickness. Maximum temperature gradients measured between regions of the composite did not exceed 10 degrees C for any given composite thickness. The most significant temperature variation was measured between the mid-thickness plies and the tool-side surface plies. Although through thickness temperature variation during cure was small, a measureable variation in coupon glass transition temperature was recorded between the tool side plies and the remainder of the part, prior to post cure. Thermal and mechanical behavior of coupons taken from segments through the thickness of the part were comparable following a post-cure cycle.
Miller, Sandi↗
Electrical Resistance Sensing of Epoxy Curing Using an Embedded Carbon Nanotube Yarn
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Omar Rodríguez-Uicab↗
Dielectric cure monitoring: Preliminary studies
Preliminary studies have been conducted on two types of dielectric cure monitoring systems employing both epoxy resins and phenolic composites. An Audrey System was used for 23 cure monitoring runs with very limited success. Nine complete cure monitoring runs have been investigated using a Micromet System. Two additional measurements were performed to investigate the Micromet's sensitivity to water absorption in a post-cure carbon-phenolic material. While further work is needed to determine data significance, the Micromet system appears to show promise as a feedback control device during processing.
Goldberg, B. E.↗
Carbon-13 Labeling Used to Probe Cure and Degradation Reactions of High- Temperature Polymers
High-temperature, crosslinked polyimides are typically insoluble, intractible materials. Consequently, in these systems it has been difficult to follow high-temperature curing or long-term degradation reactions on a molecular level. Selective labeling of the polymers with carbon-13, coupled with solid nuclear magnetic resonance spectrometry (NMR), enables these reactions to be followed. We successfully employed this technique to provide insight into both curing and degradation reactions of PMR-15, a polymer matrix resin used extensively in aircraft engine applications.
Meador, Mary Ann B.↗
Tandem CO 2 valorisation to polycarbonate vitrimer and ethylene carbonate
The need for renewably sourced polymers has intensified with the worsening of global challenges such as emissions and plastic pollution. Here, we report a CO 2 -based poly(cyclohexene carbonate) (PCHC) vitrimer cured with zinc stearate that directly addresses both issues. Enhanced zinc dispersion within the network enabled faster curing and reprocessing than possible with zinc acetate systems, while maintaining consistent T g and mechanical integrity across multiple cycles. The vitrimer undergoes rapid glycolysis in ethylene glycol, valorisation into ethylene carbonate with up to 97% yield without additional catalyst. When applied to carbon fibre-reinforced polymers (CFRPs), applying this strategy enabled the development of sustainable CO 2 -based CFRP that can undergo full resin valorisation and recovery of clean, damage-free fibres. Collectively, this tandem CO 2 valorisation strategy—from vitrimer synthesis to fibre-reinforced composites and subsequent chemical valorisation—establishes multiple recycling and valorisation pathways and provides a promising routte for carbon capture and utilization as well as material recycling.
36 MATERIALS SCIENCE↗
The Manufacturing Process for the NASA Composite Crew Module Demonstration Structure
This paper will describe the approaches and methods selected in fabrication of a carbon composite demonstration structure for the Composite Crew Module (CCM) Program. The program is managed by the NASA Safety and Engineering Center with participants from ten NASA Centers and AFRL. Multiple aerospace contractors are participating in the design development, tooling and fabrication effort as well. The goal of the program is to develop an agency wide design team for composite habitable spacecraft. The specific goals for this development project are: a).To gain hands on experience in design, building and testing a composite crew module. b) To validate key assumptions by resolving composite spacecraft design details through fabrication and testing of hardware. This abstract is based on Preliminary Design data..The final design will continue to evolve through the fall of 2007 with fabrication mostly completed by conference date. From a structures perspective, the.CCM can be viewed as a pressure module with variable pressure time histories and a series of both impact and quasi-static, high intensity point, line, and area distributed loads. The portion of the overall space vehicle being designed and. fabricated by the CCM team is just the pressure module and primary loading points. The heaviest point loads are applied and distributed to the pressure module at.an aluminum Service Module/Alternate Launch Abort System (SM/ALAS) fittings and at Main and Drogue Chute fittings. Significant line loads with metal to metal impact is applied at.the Lids ring. These major external point and line loads as well as pressure impact loads (blast and water landing) are applied to the lobed floor though the reentry shield and crushable materials. The pressure module is divided into upper and lower. shells that mate together with a bonded belly band splice joint to create the completed structural assembly. The benefits of a split CCM far outweigh the risks of a joint. These benefits include lower tooling cost and less manufacturing risk. Assembly of the top and bottom halves of the pressure shell will allow access to the interior of the shell throughout remaining fabrication sequence and can also potentially permit extensive installation of equipment and .crew facilities prior to final assembly of the two shell halves. A Pi pre-form is a woven carbon composite material which is provided in pre-impregnated form and frozen for long term storage. The cross-section shape allows the top of the pi to be bonded to a flat or curved surface with a second flat plate composite section bonded between two upstanding legs of the Pi. One of the regions relying on the merits of the Pi pre-form is the backbone. All connections among plates of the backbone structure, including the upper flanges, and to the lobe base of the pressure shell are currently joined by Pi pre-forms. The intersection of backbone composite plates is formed by application of two Pi pre-forms, top flanges and lobed surfaces are bonded with one Pi pre-form. The process of applying the pre-impregnated pi-preform will be demonstrated to include important steps like surface preparation, forming, application of pressure dams, vacuum bagging for consolidation, and curing techniques. Chopped carbon fiber tooling was selected over other traditional metallic and carbon fiber tooling. The requirement of schedule and cost economy for a moderate reuse cure tool warranted composite tooling options. Composite tooling schedule duration of 18 weeks compared favorably against other metallic tooling including invar tooling. Composite tooling also shows significant cost savings over low CTE metallic options. The composite tooling options were divided into two groups and the final decision was based on the cost, schedule, tolerance, temperature, and reuse requirements.
Pelham, Larry↗
Monitoring of Curing and Cyclic Thermoresistive Response Using Monofilament Carbon Nanotube Yarn Silicone Composites
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Tannaz Tayyarian↗
Resin Film Infusion (RFI) Process Modeling for Large Transport Aircraft Wing Structures
This investigation completed the verification of a three-dimensional resin transfer molding/resin film infusion (RTM/RFI) process simulation model. The model incorporates resin flow through an anisotropic carbon fiber preform, cure kinetics of the resin, and heat transfer within the preform/tool assembly. The computer model can predict the flow front location, resin pressure distribution, and thermal profiles in the modeled part. The formulation for the flow model is given using the finite element/control volume (FE/CV) technique based on Darcy's Law of creeping flow through a porous media. The FE/CV technique is a numerically efficient method for finding the flow front location and the fluid pressure. The heat transfer model is based on the three-dimensional, transient heat conduction equation, including heat generation. Boundary conditions include specified temperature and convection. The code was designed with a modular approach so the flow and/or the thermal module may be turned on or off as desired. Both models are solved sequentially in a quasi-steady state fashion. A mesh refinement study was completed on a one-element thick model to determine the recommended size of elements that would result in a converged model for a typical RFI analysis. Guidelines are established for checking the convergence of a model, and the recommended element sizes are listed. Several experiments were conducted and computer simulations of the experiments were run to verify the simulation model. Isothermal, non-reacting flow in a T-stiffened section was simulated to verify the flow module. Predicted infiltration times were within 12-20% of measured times. The predicted pressures were approximately 50% of the measured pressures. A study was performed to attempt to explain the difference in pressures. Non-isothermal experiments with a reactive resin were modeled to verify the thermal module and the resin model. Two panels were manufactured using the RFI process. One was a stepped panel and the other was a panel with two 'T' stiffeners. The difference between the predicted infiltration times and the experimental times was 4% to 23%.
Loos, Alfred C.↗