View All Items

$Fatigue and fracture of foam cores used in sandwich composites$

Title: Fatigue and fracture of foam cores used in sandwich composites.
Creator: Saenz, Elio., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This study focused on the fracture and fatigue crack growth behavior in polyvinylchloride (PVC) and polyethersulfone (PES) foams. A new sandwich double cantilever beam (DCB) test specimen was implemented. Elastic foundation and finite element analysis and experimental testing confirmed that the DCB specimen is appropriate for static and cyclic crack propagation testing of soft polymer foams. A comprehensive experimental mechanical analysis was conducted on PVC foams of densities ranging from...
Show moreThis study focused on the fracture and fatigue crack growth behavior in polyvinylchloride (PVC) and polyethersulfone (PES) foams. A new sandwich double cantilever beam (DCB) test specimen was implemented. Elastic foundation and finite element analysis and experimental testing confirmed that the DCB specimen is appropriate for static and cyclic crack propagation testing of soft polymer foams. A comprehensive experimental mechanical analysis was conducted on PVC foams of densities ranging from 45 to 100 kg/m3 and PES foams of densities ranging from 60 to 130 kg/m3. An in-situ scanning electron microscope study on miniature foam fracture specimens showed that crack propagation in the PVC foam was inter-cellular and in the PES foam, failure occurred predominately by extensional failure of vertical cell edges. Sandwich DCB specimens were loaded cyclically as well. For the PVC foams, the crack growth rates were substantially influenced by the density. For the PES foams, there was no clear indication about the influence of foam density on the crack growth rate.
Show less
Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3352829
Subject Headings: Sandwich construction, Composite materials, Fibrous composites, Strains and stresses, Management, Laminated materials, Plastics, Fatigue
Format: Document (PDF)

Title: Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete.
Creator: Nam, Jingak., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH...
Show moreEffects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on the rebar. Fourth, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. This tendency for corrosion initiation increased in proportion to void size irrespective of specimen type. Also, [Cl -]th decreased with increasing void diameter. In addition, new ex-situ leaching method for determining concrete pore water alkalinity was developed.
Show less
Date Issued: 2004
PURL: http://purl.flvc.org/fcla/dt/12096
Subject Headings: Reinforced concrete construction, Chlorides, Steel--Corrosion, Composite reinforced concrete
Format: Document (PDF)

Title: Enhancement of spike and stab resistance of flexible armor using nanoparticles and a cross-linking fixative.
Creator: Lambert, Vincent., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A novel approach has been introduced in making flexible armor composites. Armor composites are usually made by reinforcing Kevlar fabric into the mixture of a polymer and nanoscale particles. The current procedure deviates from the traditional shear thickening fluid (STF) route and instead uses silane (amino-propyl-trimethoxy silane) as the base polymer. In addition, a cross-linking fixative such as Glutaraldehyde (Gluta) is added to the polymer to create bridges between distant pairs of...
Show moreA novel approach has been introduced in making flexible armor composites. Armor composites are usually made by reinforcing Kevlar fabric into the mixture of a polymer and nanoscale particles. The current procedure deviates from the traditional shear thickening fluid (STF) route and instead uses silane (amino-propyl-trimethoxy silane) as the base polymer. In addition, a cross-linking fixative such as Glutaraldehyde (Gluta) is added to the polymer to create bridges between distant pairs of amine groups present in Kevlar and silated nanoparticles. Water, silane, nanoparticles and Gluta are mixed using a homogenizer and an ultra-sonochemical technique. Subsequently, the admixture is impregnated with Kevlar - bypassing the heating and evaporating processes involved with STF. The resulting composites have shown remarkable improvement in spike resistance; at least one order higher than that of STF/Kevlar composites. The source of improvement has been traced to the formation of secondary amine C-N stretch due to the presence of Gluta.
Show less
Date Issued: 2009
PURL: http://purl.flvc.org/FAU/186769
Subject Headings: Armor, Design and construction, Composite materials, Testing, Nanoparticles, Testing, Viscoelasticity
Format: Document (PDF)

Title: Feasibility of using carbon fiber reinforced plastic tendons in prestressed concrete Double-Tee bridge system.
Creator: Zhuang, Ming., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: One of the major problems the construction industry faces today is corrosion of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Fiber reinforced plastics (FRPs) are highly regarded as prospective replacement for steel in prestressed concrete structures under corrosive environment. This investigation was conducted to establish the feasibility of using Carbon Fiber Composite (CFC) cables as reinforcing/prestressing elements in concrete...
Show moreOne of the major problems the construction industry faces today is corrosion of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Fiber reinforced plastics (FRPs) are highly regarded as prospective replacement for steel in prestressed concrete structures under corrosive environment. This investigation was conducted to establish the feasibility of using Carbon Fiber Composite (CFC) cables as reinforcing/prestressing elements in concrete bridge structures. Besides investigating durability of CFC cables and pretensioned concrete beams with CFC cables in adverse environments (alkali and seawater), flexure and shear tests were performed on single Double-Tee beams, together with service load behavior, fatigue strength and ultimate load capacity tests on a half scale model Double-Tee girder bridge system prestressed with CFC cables. Exposure to seawater and alkali environments has no adverse effect on the strength of the CFRP tendons as well as the pretensioned beams with CFRP. Based on the flexural strength tests on Double-Tee beams, the bond between CFRP tendons and concrete is satisfactory. The Double-Tee bridge system exhibited good fatigue resistance and adequate ductility under ultimate load conditions. The ultimate load capacity of the bridge is approximately three times the service load corresponding to two HS20-44 trucks and equals 2.4 times the first crack load. Finite element analyses were carried out to predict elastic deformations and collapse load of the Double-Tee bridge prestressed with CFC cables. Feasibility of using CFC cables in bridge structures is assessed based on the experimental and analytical parameters such as deflections, strains, crack distributions and crack widths.
Show less
Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/12465
Subject Headings: Carbon fibers, Composite construction, Fiber reinforced plastics, Bridges, Iron and steel, Reinforced concrete construction, Prestressed concrete construction
Format: Document (PDF)

Title: Centrally prestressed fiber reinforced concrete columns.
Creator: Grijalba, Daniel A., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: With the need to improve corrosion resistance in columns and piles, the innovative idea of Centrally Prestressed Fiber Reinforced Concrete (CPFRC) columns is a promising solution. The first step is to compare if the compressive strength of any mix is affected by the size, geometry, or even the inclusion of polyolefin fibers in a specimen. The results showed that the cylinder size of 4 in. x 8 in., which is the most common size used by the testing labs, has the highest compressive strength....
Show moreWith the need to improve corrosion resistance in columns and piles, the innovative idea of Centrally Prestressed Fiber Reinforced Concrete (CPFRC) columns is a promising solution. The first step is to compare if the compressive strength of any mix is affected by the size, geometry, or even the inclusion of polyolefin fibers in a specimen. The results showed that the cylinder size of 4 in. x 8 in., which is the most common size used by the testing labs, has the highest compressive strength. There was no sign on compressive strength improvement with the use of polyolefin fibers, except for reduction in cracking size and concrete spalling. The second step compared the ultimate strength, ductility characteristics and failure mode of CPFRC columns to conventional columns. CPFRC showed adequate axial and flexural resistance, in addition to ductile behavior similar to regular reinforced concrete columns.
Show less
Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3332253
Subject Headings: Prestressed concrete construction, Strength of materials, Composite reinforced concrete, Concrete, Chemical resistance
Format: Document (PDF)

Title: Durability prediction of recycled aggregate concrete under accelerated aging and environmental exposure.
Creator: Gonzalez, Lillian, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: This study is to compare the performance of recycled aggregate concrete and the impact of up to 50% cement replacement with fly ash on durability. Water content, sieve analysis, standard and modified compaction tests were performed to assess the physical properties of the recycled aggregate concrete. Accelerated aging tests were performed to predict the long term durability of the recycled aggregate concrete. Following Arrhenius modeling and TTS and SIM accelerated aging protocols, a time...
Show moreThis study is to compare the performance of recycled aggregate concrete and the impact of up to 50% cement replacement with fly ash on durability. Water content, sieve analysis, standard and modified compaction tests were performed to assess the physical properties of the recycled aggregate concrete. Accelerated aging tests were performed to predict the long term durability of the recycled aggregate concrete. Following Arrhenius modeling and TTS and SIM accelerated aging protocols, a time versus stiffness master curve was created. This allowed the prediction of equivalent age using experimental data and theoretical analysis. To account for environmental exposure, the specimens underwent 24 and 48 hours of wet-dry cycling and subjected. Overall there was an increase in stiffness and strength from the specimens containing fly ash. All tests performed predicted equivalent age beyond the testing period of 144 hrs. and up to 7 years. Specimens containing fly maintained a constant and higher density to environmental exposure.
Show less
Date Issued: 2010
PURL: http://purl.flvc.org/FAU/3353087
Subject Headings: Concrete, Mechanical properties, Testing, Concrete, Environmental aspects, Sustainable construction, High strength concrete, Testing, Cement composites, Testing
Format: Document (PDF)

Title: Strength and durability of fly ash-based fiber-reinforced geopolymer concrete in a simulated marine environment.
Creator: Martinez Rivera, Francisco Javier, Sobhan, Khaled, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: This research is aimed at investigating the corrosion durability of polyolefin fiber-reinforced fly ash-based geopolymer structural concrete (hereafter referred to as GPC, in contradistinction to unreinforced geopolymer concrete referred to as simply geopolymer concrete), where cement is completely replaced by fly ash, that is activated by alkalis, sodium hydroxide and sodium silicate. The durability in a marine environment is tested through an electrochemical method for accelerated corrosion...
Show moreThis research is aimed at investigating the corrosion durability of polyolefin fiber-reinforced fly ash-based geopolymer structural concrete (hereafter referred to as GPC, in contradistinction to unreinforced geopolymer concrete referred to as simply geopolymer concrete), where cement is completely replaced by fly ash, that is activated by alkalis, sodium hydroxide and sodium silicate. The durability in a marine environment is tested through an electrochemical method for accelerated corrosion. The GPC achieved compressive strengths in excess of 6,000 psi. Fiber reinforced beams contained polyolefin fibers in the amounts of 0.1%, 0.3%, and 0.5% by volume. After being subjected to corrosion damage, the GPC beams were analyzed through a method of crack scoring, steel mass loss, and residual flexural strength testing. Fiber reinforced GPC beams showed greater resistance to corrosion damage with higher residual flexural strength. This makes GPC an attractive material for use in submerged marine structures.
Show less
Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004037
Subject Headings: Concrete mixing -- Quality control, Green chemistry, Polymer composites, Reinforced concrete -- Corrosion -- Testing, Reinforced concrete construction
Format: Document (PDF)

Title: Feasibility studies on carbon fiber composite cables in reinforced/prestressed concrete structures.
Creator: Kanneganti, Srikanth., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The feasibility studies on the use of non-metallic continuous fiber reinforcement in reinforced and prestressed concrete structures are presented herein. Experimental results from studies on relaxation, bond and transfer length of Carbon Fiber Composite Cables (CFCC) are presented followed by results of flexural load tests on concrete beams reinforced and prestressed with CFCC. Durability of the CFCC is another prime concern, and hence part of the study also focuses on establishing the...
Show moreThe feasibility studies on the use of non-metallic continuous fiber reinforcement in reinforced and prestressed concrete structures are presented herein. Experimental results from studies on relaxation, bond and transfer length of Carbon Fiber Composite Cables (CFCC) are presented followed by results of flexural load tests on concrete beams reinforced and prestressed with CFCC. Durability of the CFCC is another prime concern, and hence part of the study also focuses on establishing the durability of the CFCC exposed to aggressive environments like alkali solution and sea water. The basic mechanics that govern the structural behavior of the beams, provide important insight into the potential that CFCC has to offer.
Show less
Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/15080
Subject Headings: Fiber reinforced plastics, Reinforced concrete, Fiber, Composite materials, Prestressed concrete construction--Deterioration, Carbon fibers
Format: Document (PDF)

Title: Peel-off characteristics of carbon fiber laminates bonded to concrete.
Creator: Barbosa, Mauro., Florida Atlantic University, Arockiasamy, Madasamy
Abstract/Description: This study presents the experimental and theoretical studies on debond of carbon fiber laminates bonded to concrete, which aids in understanding the mechanics of the repaired damaged prestressed concrete girders with externally bonded carbon plates. The bond strength of carbon plate specimens bonded to concrete is determined experimentally by the debond test. The initial crack is introduced in the specimens at one location, namely the plate/adhesive interface. The fracture toughness for...
Show moreThis study presents the experimental and theoretical studies on debond of carbon fiber laminates bonded to concrete, which aids in understanding the mechanics of the repaired damaged prestressed concrete girders with externally bonded carbon plates. The bond strength of carbon plate specimens bonded to concrete is determined experimentally by the debond test. The initial crack is introduced in the specimens at one location, namely the plate/adhesive interface. The fracture toughness for debonding is evaluated and expressed as the critical strain energy release rate. A finite element analysis was performed to evaluate the compliance and stress distribution in the debond test specimens.
Show less
Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12669
Subject Headings: Prestressed concrete construction--Maintenance and repair, Fracture mechanics, Carbon composites
Format: Document (PDF)

Title: Experimental and Modeling Study of Chloride Ingress into Concrete and Reinforcement Corrosion Initiation.
Creator: Yu, Hui, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Effects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to...
Show moreEffects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to verify and explain the experimental results. Based upon the results, it was determined that unexpectedly higher chloride concentrations were present on the top of the rebar trace than that to the side at the same depth and an inverse concentration gradient (increasing [Cl-] with increasing depth) occurred near the top of rebars. Also, coarse aggregate volume profile in close proximity to the rebar and spatial distribution of these aggregates, in conjunction with the physical obstruction afforded by reinforcement to chloride flow, complicates concrete sampling for Cl- intended to define the critical concentration of this species to initiate corrosion. Modeling analyses that considered cover thickness, chloride threshold concentration, reinforcement size and shape, and coarse aggregate type and percolation confirmed the experimental findings. The results, at least in part, account for the relatively wide spread in chloride corrosion threshold values reported in the literature and illustrate that more consistent chloride threshold concentrations can be acquired from mortar or paste specimens than from concrete ones.
Show less
Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012582
Subject Headings: Reinforced concrete construction--Corrosion, Chlorides--Diffusion rate, Composite reinforced concrete, Concrete--Chemical resistance
Format: Document (PDF)

Title: Study of edge effects in laminated sandwich specimens.
Creator: Mankuzhy, Pradeep Prabhakaran., Florida Atlantic University, Merry, Stephanie L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Different methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a...
Show moreDifferent methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a sandwich specimen in three point bending. However, these conventional methods failed to show the sharp strain gradient that exists near the free edge. The Force Balance Method was simplified for sandwich specimens by considering the face laminate as a homogeneous and orthotropic material with averaged properties. Simplified expressions were also obtained for calculating the boundary layer thickness. The boundary layer thickness was found to vary linearly with core thickness for the cases considered.
Show less
Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/14523
Subject Headings: Sandwich construction--Fatigue, Composite materials, Strains and stresses, Structural analysis (Engineering)
Format: Document (PDF)

Title: Concrete diffusivity and its correlation with chloride deposition rate on concrete exposed to marine environments.
Creator: Echevarria, Victor Anthony., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The aim of this study was to investigate the diffusion of chloride ions into concrete samples that were exposed in scenarios that simulate the splash, tidal, atmospheric, and immersed portions of a marine structure. To study the atmospheric deposition, the project also investigated the relationship between chloride ion deposition on the wet candle and its accumulation into concrete samples. Results from the wet candle experiment indicated that between 2% and 45% of the chlorides deposited per...
Show moreThe aim of this study was to investigate the diffusion of chloride ions into concrete samples that were exposed in scenarios that simulate the splash, tidal, atmospheric, and immersed portions of a marine structure. To study the atmospheric deposition, the project also investigated the relationship between chloride ion deposition on the wet candle and its accumulation into concrete samples. Results from the wet candle experiment indicated that between 2% and 45% of the chlorides deposited per square meter of exposed area could be found within the concrete samples. After 6 months, slag G1a blocks showed the most resistance to chloride penetration in the tidal and splash simulations. After 10 months of exposure, fly ash samples had the slowest rates of diffusion in the tidal simulation while the fly ash + silica fume samples and the slag samples measured similar rates of diffusion within the tidal zone. After 90 days of curing, cylinders composed of 20% fly ash & 8% silica fume measured the highest average resistivity values and were found to be less vulnerable to chloride ion penetration than the 20% fly ash and the 50% slag concrete through rapid migration tests.
Show less
Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3358557
Subject Headings: Reinforced concrete, Construction, Corrosion, Composite reinforced concrete, Corrosion, Testing, Concrete, Fluid dynamics, Concrete, Chemical resistance, Chlorides, Diffusion rate
Format: Document (PDF)

Title: Experimental evaluation of the durability of fly ash-based geopolymer concrete in the marine environment.
Creator: Edouard, Jean-Baptiste., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: The construction industry is increasingly turning to the use of environmentally friendly materials in order to meet the sustainable aspect required by modern infrastructures. Consequently, for the last two decades, the expansion of this concept, and the increasing global warming have raised concerns on the extensive use of Portland cement due to the high amount of carbon dioxide gas associated with its production. The development of geopolymer concretes offers promising signs for a change in...
Show moreThe construction industry is increasingly turning to the use of environmentally friendly materials in order to meet the sustainable aspect required by modern infrastructures. Consequently, for the last two decades, the expansion of this concept, and the increasing global warming have raised concerns on the extensive use of Portland cement due to the high amount of carbon dioxide gas associated with its production. The development of geopolymer concretes offers promising signs for a change in the way of producing concrete. However, to seriously consider geopolymer binders as an alternative to ordinary Portland cement, the durability of this new material should be evaluated in any comparative analysis. The main purpose of this study was to evaluate the durability characteristics of low calcium fly ash-based geopolymer concretes subjected to the marine environment, compared to ordinary Portland cement concrete with similar exposure. To achieve this goal, 8 molar geopolymer, 14 molar geopolymer and ordinary Portland cement concrete mixes were prepared and tested for exposure in seawater. Compressive strengths in the range of 2900 to 8700 psi (20-60 MPa) were obtained. The corrosion resistance performance of steel-reinforced concrete beams, made of these mixes, was also studied, using an accelerated electrochemical method, with submergence in salt water. The test results indicated that the geopolymer concrete showed excellent resistance to chloride attack, with longer time to corrosion cracking, compared to ordinary Portland cement concrete.
Show less
Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3170960
Subject Headings: Reinforced concrete, Corrosion, Testing, Reinforced concrete construction, Concrete, Mixing, Quality control, Environmental chemistry, Industrial applications, Polymer composites
Format: Document (PDF)

Title: Fatigue modeling of composite ocean current turbine blade.
Creator: Akram, Mohammad Wasim, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The success of harnessing energy from ocean current will require a reliable structural design of turbine blade that is used for energy extraction. In this study we are particularly focusing on the fatigue life of a 3m length ocean current turbine blade. The blade consists of sandwich construction having polymeric foam as core, and carbon/epoxy as face sheet. Repetitive loads (Fatigue) on the blade have been formulated from the randomness of the ocean current associated with turbulence and...
Show moreThe success of harnessing energy from ocean current will require a reliable structural design of turbine blade that is used for energy extraction. In this study we are particularly focusing on the fatigue life of a 3m length ocean current turbine blade. The blade consists of sandwich construction having polymeric foam as core, and carbon/epoxy as face sheet. Repetitive loads (Fatigue) on the blade have been formulated from the randomness of the ocean current associated with turbulence and also from velocity shear. These varying forces will cause a cyclic variation of bending and shear stresses subjecting to the blade to fatigue. Rainflow Counting algorithm has been used to count the number of cycles within a specific mean and amplitude that will act on the blade from random loading data. Finite Element code ANSYS has been used to develop an S-N diagram with a frequency of 1 Hz and loading ratio 0.1 Number of specific load cycles from Rainflow Counting in conjunction with S-N diagram from ANSYS has been utilized to calculate fatigue damage up to 30 years by Palmgren-Miner's linear hypothesis.
Show less
Date Issued: 2010
PURL: http://purl.flvc.org/FAU/2867332
Subject Headings: Turbines, Blades, Materials, Fatigue, Marine turbines, Mathematical models, Structural dynamics, Composite materials, Mathematical models, Sandwich construction, Fatigue
Format: Document (PDF)

Title: Experimental Evaluation of the Structural Integrity of the Repairs for Corrosion-Damaged Marine Piles.
Creator: Bolivar, Juan Carlos, Reddy, Dronnadula V., Florida Atlantic University
Abstract/Description: Corrosion damage is the mam cause of deterioration for reinforced concrete marine structures. Given the current economic downturn, it has become increasingly important to repair existing structures with techniques that prolong their life-cycle. The process to identify suitable repairs is affected by the lack of a consistent methodology to predict the outcome of the repairs. This investigation intends to compare the performance of seven different repairs, in terms of corrosion resistance,...
Show moreCorrosion damage is the mam cause of deterioration for reinforced concrete marine structures. Given the current economic downturn, it has become increasingly important to repair existing structures with techniques that prolong their life-cycle. The process to identify suitable repairs is affected by the lack of a consistent methodology to predict the outcome of the repairs. This investigation intends to compare the performance of seven different repairs, in terms of corrosion resistance, structural integrity, and cost-effectiveness. Following initial exposure to corrosion, the specimens were repaired using the proposed techniques. They were then tested for durability under simulated tidal conditions with periodic corrosion monitoring. The structural integrity was evaluated by crack scoring and ultimate load testing, and a comprehensive evaluation matrix was prepared, to determine which repairs were most adequate for corrosion damage. The results of this investigation substantiate that the repairs including carbon wrapping, HDPE jacketing, and MMFX steel, outperformed the rest of the repairs.
Show less
Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00012506
Subject Headings: Reinforced concrete--Corrosion, Underwater concrete construction--Maintenance and repair, Materials--Deterioration--Prevention, Fibrous composites--Evaluation
Format: Document (PDF)

Title: Development of a Comprehensive Design Methodology and Fatigue Life Prediction of Composite Turbine Blades under Random Ocean Current Loading.
Creator: Suzuki, Takuya, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A comprehensive study was performed to overcome the design issues related to Ocean Current Turbine (OCT) blades. Statistical ocean current models were developed in terms of the probability density function, the vertical profile of mean velocity, and the power spectral density. The models accounted for randomness in ocean currents, tidal effect, and ocean depth. The proposed models gave a good prediction of the velocity variations at the Florida Straits of the Gulf Stream. A novel procedure...
Show moreA comprehensive study was performed to overcome the design issues related to Ocean Current Turbine (OCT) blades. Statistical ocean current models were developed in terms of the probability density function, the vertical profile of mean velocity, and the power spectral density. The models accounted for randomness in ocean currents, tidal effect, and ocean depth. The proposed models gave a good prediction of the velocity variations at the Florida Straits of the Gulf Stream. A novel procedure was developed to couple Fluid-Structure Interaction (FSI) with blade element momentum theory. The FSI effect was included by considering changes in inflow velocity, lift and drag coefficients of blade elements. Geometric non-linearity was also considered to account for large deflection. The proposed FSI analysis predicted a power loss of 3.1 % due to large deflection of the OCT blade. The method contributed to saving extensive computational cost and time compared to a CFD-based FSI analysis. The random ocean current loadings were calculated by considering the ocean current turbulence, the wake flow behind the support structure, and the velocity shear. The random ocean current loadings had large probability of high stress ratio. Fatigue tests of GFRP coupons and composite sandwich panels under such random loading were performed. Fatigue life increased by a power function for GFRP coupons and by a linearlog function for composite sandwich panels as the mean velocity decreased. To accurately predict the fatigue life, a new fatigue model based on the stiffness degradation was proposed. Fatigue life of GFRP coupons was predicted using the proposed model, and a comparison was made with experimental results. As a summary, a set of new design procedures for OCT blades has been introduced and verified with various case studies of experimental turbines.
Show less
Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00005931
Subject Headings: Dissertations, Academic -- Florida Atlantic University, Turbines--Blades--Design and construction., Turbines--Blades--Materials., Composite construction--Fatigue., Ocean currents--Mathematical models.
Format: Document (PDF)

Title: Theoretical analysis of reinforced and prestressed concrete bridge members strengthened with CFRP laminates.
Creator: Qu, Rong., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Nonlinear finite element analyses of the reinforced rectangular beams, prestressed solid slab and prestressed voided slab retrofitted with CFRP laminates are carried out using the software ANSYS(version 5.0) on the Sunwork station. The computer analyses are based on the proposed stress-strain relationship considering the effects of tensile stress on both elastic modulus and maximum compressive stress of concrete. Several assumptions are made in predicting the loss of tensile strength due to...
Show moreNonlinear finite element analyses of the reinforced rectangular beams, prestressed solid slab and prestressed voided slab retrofitted with CFRP laminates are carried out using the software ANSYS(version 5.0) on the Sunwork station. The computer analyses are based on the proposed stress-strain relationship considering the effects of tensile stress on both elastic modulus and maximum compressive stress of concrete. Several assumptions are made in predicting the loss of tensile strength due to crack, confinement due to the laminate bonding, tensile strength due to the prestress force, failure pattern due to the concentrated stress adjacent to the loading point and concrete crushing due to large compressive strain. A subroutine is developed using macro commands of ANSYS. In this research, Branson's equation or Ie procedure is assumed in the prediction of deflection of retrofitted concrete members. The modifications needed due to laminate bonding are the cracking moments of inertia (Icr) of the beams or slabs bonded with CFRP laminates, which are included in the analysis.
Show less
Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/15083
Subject Headings: ANSYS (Computer system), Reinforced concrete--Plastic properties, Carbon composites, Fiber reinforced plastics, Bridges--Design and construction, Prestressed concrete construction
Format: Document (PDF)

Title: Evaluation of Chloride Threshold for Steel Fiber Reinforced Concrete Composited in Aggressively Corrosive Environments.
Creator: Vogel, Dietrich H., Presuel-Moreno, Francisco, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Highway drainage pipes utilize concrete reinforced with steel wire to help mitigate water, earth, and traffic loads. Drainage pipes reinforced with zinc electroplated steel fibers offer a lower steel alternative to traditional steel wire cage reinforcements. The objective of the thesis research was to determine the physical and electrochemical characteristics of zinc electroplated steel fiber corrosion propagation. Experimental programs include: Fracture analysis of zinc electroplated steel...
Show moreHighway drainage pipes utilize concrete reinforced with steel wire to help mitigate water, earth, and traffic loads. Drainage pipes reinforced with zinc electroplated steel fibers offer a lower steel alternative to traditional steel wire cage reinforcements. The objective of the thesis research was to determine the physical and electrochemical characteristics of zinc electroplated steel fiber corrosion propagation. Experimental programs include: Fracture analysis of zinc electroplated steel fibers embedded in dry-cast concrete pipes exposed to varying chloride concentrations; Visual analysis of zinc electroplated steel fibers embedded in concrete exposed to varying chloride concentrations; Electrochemical analysis of zinc electroplated steel fibers embedded in concrete exposed to varying chlorides; Chloride threshold determination for zinc electroplated steel fibers immersed in simulated pore solution. Between the four experimental programs the most significant conclusion is that oxygen, moisture, and chlorides past the chloride threshold must be present for corrosion to propagate significantly on the zinc electroplated steel fibers.
Show less
Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004637, http://purl.flvc.org/fau/fd/FA00004637
Subject Headings: Fiber-reinforced concrete--Cracking., Cement composites., Reinforced concrete construction., Reinforced concrete--Corrosion., Corrosion and anti-corrosives., Structural engineering.
Format: Document (PDF)

Title: Accelerated Testing Protocol for Durability of Roller Compacted Recycled Aggregate Concrete (RCRAC).
Creator: Fraser, Jamie Barbara, Sobhan, Khaled Dr., Florida Atlantic University
Abstract/Description: With the growing environmental concerns related to the ever increasing waste disposal problem in the US, the utilizing of recycled materials in Civil Engineering construction has become an attractive option, which not only supports the concept of green buildings, but can also bring about economic savings by conserving natural resources and landfill spaces. However, the questionable long-term performance of recycled materials often hinders the widespread use in structural applications. The...
Show moreWith the growing environmental concerns related to the ever increasing waste disposal problem in the US, the utilizing of recycled materials in Civil Engineering construction has become an attractive option, which not only supports the concept of green buildings, but can also bring about economic savings by conserving natural resources and landfill spaces. However, the questionable long-term performance of recycled materials often hinders the widespread use in structural applications. The primary focus of this study was to develop accelerated aging/testing protocols for predicting the durability of recycled aggregate concrete (RAC), Type I Portland Cement, and up to 50% fly ash replacement. Accelerated aging was accomplished by curing the specimens at elevated temperatures regimes for specific durations. Stiffness-time master curves were constructed using Time-Temperature Superposition (TTS) and Stepped Isothermal Method (SIM) based on the Arrhenius Equation. All the methods demonstrated that the stiffness decreased with time regardless of the amount of fly ash. The Arrhenius method allowed stiffness prediction up to an equivalent age of 14,000 hours developed from short-term tests lasting up to 144 hours. It was also found that SIM and TTS provide equitable results, potentially reducing the number of specimens and testing time for durability prediction.
Show less
Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00012517
Subject Headings: Joints (Engineering)--Testing, High strength concrete--Testing, Concrete--Mechanical properties--Testing, Concrete construction, Cement composites--Testing
Format: Document (PDF)

Composite materials (5)	+ -
Composite reinforced concrete (4)	+ -
Concrete (4)	+ -
Reinforced concrete construction (4)	+ -
Testing (4)	+ -

Fiber reinforced plastics (3)	+ -
Prestressed concrete construction (3)	+ -
Carbon composites (2)	+ -
Carbon fibers (2)	+ -
Chemical resistance (2)	+ -
Chlorides (2)	+ -
Corrosion (2)	+ -
Fatigue (2)	+ -
Polymer composites (2)	+ -
Reinforced concrete (2)	+ -
Sandwich construction (2)	+ -
Strains and stresses (2)	+ -
ANSYS (Computer system) (1)	+ -
Armor (1)	+ -
Blades (1)	+ -
Bridges, Iron and steel (1)	+ -
Bridges--Design and construction (1)	+ -
Cement composites (1)	+ -
Cement composites--Testing (1)	+ -
Cement composites. (1)	+ -
Chlorides--Diffusion rate (1)	+ -
Composite construction (1)	+ -
Composite construction--Fatigue. (1)	+ -
Concrete construction (1)	+ -
Concrete mixing -- Quality control (1)	+ -

College of Engineering and Computer Science (16)	+ -
Department of Ocean and Mechanical Engineering (12)	+ -
Florida Atlantic University (11)	+ -
Arockiasamy, Madasamy (4)	+ -
Department of Civil, Environmental and Geomatics Engineering (4)	+ -

Hartt, William H. (2)	+ -
Akram, Mohammad Wasim (1)	+ -
Barbosa, Mauro. (1)	+ -
Bolivar, Juan Carlos (1)	+ -
Echevarria, Victor Anthony. (1)	+ -
Edouard, Jean-Baptiste. (1)	+ -
Fraser, Jamie Barbara (1)	+ -
Gonzalez, Lillian (1)	+ -
Grijalba, Daniel A. (1)	+ -
Kanneganti, Srikanth. (1)	+ -
Lambert, Vincent. (1)	+ -
Mahfuz, Hassan (1)	+ -
Mankuzhy, Pradeep Prabhakaran. (1)	+ -
Martinez Rivera, Francisco Javier (1)	+ -
Merry, Stephanie L. (1)	+ -
Nam, Jingak. (1)	+ -
Presuel-Moreno, Francisco (1)	+ -
Qu, Rong. (1)	+ -
Reddy, Dronnadula V. (1)	+ -
Saenz, Elio. (1)	+ -
Sobhan, Khaled (1)	+ -
Sobhan, Khaled Dr. (1)	+ -
Suzuki, Takuya (1)	+ -
Vogel, Dietrich H. (1)	+ -
Yu, Hui (1)	+ -

Search In

Sort Results By:

Narrow results by:

Collection

Topical Subject

Genre

Type of Resource

Language

Creator

Format

Owner