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Title: Numerical Simulation of Composite Ship under Hydrodynamic load using Fluid Structure Interactions.
Creator: Ma, Siyuan, Mahfuz, Hassan, Graduate College
Date Issued: 2011-04-08
PURL: http://purl.flvc.org/fcla/dt/3172436
Subject Headings: Composite materials, Ships --Materials, Fluid-structure interaction
Format: Document (PDF)

Title: Nano-sensors for explosives detection.
Creator: Davis, Charles, Mahfuz, Hassan, Langston, Tye A., Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361289
Subject Headings: Improvised explosive devices, Improvised explosive devices--Detection
Format: Document (PDF)

Title: Analysis of carbon nanotube/epoxy composite in the presence of an interphase layer.
Creator: Sabet, Seyed Morteza, Mahfuz, Hassan, Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361347
Subject Headings: Nanotubes, Carbon, Nanotubes--Analysis
Format: Document (PDF)

Title: Finite element simulation of composite ship structures under wave loads and slamming loads.
Creator: Rahman, Md Hafizur, Mahfuz, Hassan, Graduate College
Date Issued: 2013-04-12
PURL: http://purl.flvc.org/fcla/dt/3361345
Subject Headings: Hulls (Naval architecture), Hulls (Naval architecture)--Design and construction
Format: Document (PDF)

Title: The effects of POSS surface treatment on the interlaminar property of marine composites.
Creator: Powell, Felicia M., Granata, Richard D., Hosur, Mahesh, Mahfuz, Hassan, Graduate College
Date Issued: 2011-04-08
PURL: http://purl.flvc.org/fcla/dt/3164682
Subject Headings: Composite materials --Delamination, Fibrous composites, Polymers --Effect of radiation on
Format: Document (PDF)

Title: Magnetic alignment of swcnt(cooh)s coated by fe3o4 in sc-15 epoxy and anisotropy of physical properties.
Creator: Malkina, Olga, Sorge, Korey D., Rangari, V. K., Graduate College, Mahfuz, Hassan
Date Issued: 2011-04-08
PURL: http://purl.flvc.org/fcla/dt/3164623
Subject Headings: Anisotropy, Electromagnetism, Nanotubes
Format: Document (PDF)

Title: Coating of Carbon Fiber with Polyhedral Oligomeric Silsesquioxane (POSS) to Enhance Mechanical Properties and Durability of Carbon/Vinyl Ester Composites.
Creator: Mahfuz, Hassan, Powell, Felicia M., Granata, Richard D., Hosur, Mahesh, Khan, Mujib
Abstract/Description: Our continuing quest to improve the performance of polymer composites under moist and saltwater environments has gained momentum in recent years with the reinforcement of inorganic nanoparticles into the polymer. The key to mitigate degradation of composites under such environments is to maintain the integrity of the fiber/matrix (F/M) interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by coating the carbon fiber with polyhedral oligomeric...
Show moreOur continuing quest to improve the performance of polymer composites under moist and saltwater environments has gained momentum in recent years with the reinforcement of inorganic nanoparticles into the polymer. The key to mitigate degradation of composites under such environments is to maintain the integrity of the fiber/matrix (F/M) interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by coating the carbon fiber with polyhedral oligomeric silsesquioxane (POSS). POSS is a nanostructured inorganic-organic hybrid particle with a cubic structure having silicon atoms at the core and linked to oxygen atoms. The advantage of using POSS is that the silicon atoms can be linked to a substituent that can be almost any chemical group known in organic chemistry. Cubic silica cores are ‘hard particles’ and are about 0.53 nm in diameter. The peripheral organic unit is a sphere of about 1–3 nm in diameter. Further, cubic structure of POSS remains intact during the polymerization process and therefore with appropriate functional groups, if installed on the fiber surface, would provide a stable and strong F/M interface. Two POSS systems with two different functional groups; namely, octaisobutyl and trisilanolphenyl have been investigated. A set of chemical and mechanical procedures has been developed to coat carbon fibers with POSS, and to fabricate layered composites with vinyl ester resin. Interlaminar shear and low velocity impact tests have indicated around 17–38% improvement in mechanical properties with respect to control samples made without the POSS coating. Saltwater and hygrothermal tests at various environmental conditions have revealed that coating with POSS reduces water absorption by 20–30% and retains the composite properties.
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Date Issued: 2011-09-21
PURL: http://purl.flvc.org/fau/fd/FAUIR000082
Format: Citation

Title: Development of Flexible Puncture Resistant Materials System Using Silica Nanoparticles.
Creator: Clements, Floria Eve, Mahfuz, Hassan, Florida Atlantic University
Abstract/Description: Nanoscale silica particles are functionalized and ultrasonically dispersed into a mixture of polyethylene glycol and ethanol, and then reinforced with Kevlar. The stab or puncture resistance of the flexible nanophased materials system supersedes recent advances made in this area. Through SEM scans, thermal and chemical analysis, it is evident that the functionalized nanoparticles offer multiple facets of resistance to penetration of a sharp impactor. The improvement in protection is traced to...
Show moreNanoscale silica particles are functionalized and ultrasonically dispersed into a mixture of polyethylene glycol and ethanol, and then reinforced with Kevlar. The stab or puncture resistance of the flexible nanophased materials system supersedes recent advances made in this area. Through SEM scans, thermal and chemical analysis, it is evident that the functionalized nanoparticles offer multiple facets of resistance to penetration of a sharp impactor. The improvement in protection is traced to the formation of siloxane bonds during functionalization. The framework for a theoretical model is established to estimate penetration depth under low velocity impact of a sharp object through the flexible composite. For comparison ofthese novel fabric composites, a method is also introduced to evaluate penetration resistance quantitatively. The method is capable of showing subtle changes that would otherwise be missed.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012513
Subject Headings: Nanostructured materials, Reinforced plastics, Fibrous composites, Nanotechnology
Format: Document (PDF)

Title: Enhancing Fatigue Performance of Sandwich Composites with Nanophased Core.
Creator: Zainuddin, S., Mahfuz, Hassan, Jeelani, S.
Date Issued: 2010
PURL: http://purl.flvc.org/fau/fd/FAUIR000169
Format: Citation

Title: Magnetic alignment of SWCNTs decorated with Fe3O4 to enhance mechanical properties of SC-15 epoxy.
Creator: Malkina, Olga, Mahfuz, Hassan, Sorge, Korey D., Rondinone, A., Chen, Jihua, More, K., Reeves, S., Rangari, V. K.
Date Issued: 2013-04
PURL: http://purl.flvc.org/fau/fd/FAUIR000170
Format: Citation

Title: Hybrid stress analysis using digitized photoelastic data and numerical methods.
Creator: Mahfuz, Hassan, Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Equations of stress-difference elasticity, derived from the equations of equilibrium and compatibility for a two-dimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal...
Show moreEquations of stress-difference elasticity, derived from the equations of equilibrium and compatibility for a two-dimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal connectivity within the digitized boundary for the solution of these partial differential equations. A method is introduced to digitize the photoelastic fringes, namely isochromatics and isoclinics, and to estimate the values of sigma1 - sigma2, sigma x - sigma y and tau xy at each nodal point by an interpolation technique. Interpolated values of the stress parameters are used to improve the initial estimate and hence the convergence of the iterative solution of the system of equations. Superfluous boundary conditions are added from the digitized photoelastic data for further speeding up the rate of convergence. The boundary of the domain and the photoelastic fringes are digitized by physically traversing the cursor along the boundary, and the digitized information is scanned horizontally and vertically to generate internal and boundary nodal points. A linear search determines the nodal connectivity and isolates the boundary points for the input of the boundary values. A similar scanning method estimates the photoelastic parameters at each nodal point and also finds the points closest to the tint of passage of each photoelastic fringe. Stress values at these close points are determined without interpolation and are subsequently used as superfluous boundary conditions in the iteration scheme. Successive over-relaxation is applied to the classical Gauss-Seidel method for final enhancement of the convergence of the iteration process. The iteration scheme starts with an accelerating factor other than unity and estimates the spectral radius of the iteration matrix from the two vector norms. This information is used to estimate a temporary value of the optimum relaxation parameter, omega[opt], which is used for a fixed number of iterations to approximate a better value of the accelerating factor. The process is continued until two successive estimates differ by a given tolerance or the stopping criteria are reached. Detailed techniques of developing the code for mesh generation, photoelastic data collection and boundary value interpolation to solve the elliptic boundary value problems are presented. Three separate examples with varying stress gradients and fringe patterns are presented to test the validity of the code and the overall method. Results are compared with the analytical and experimental solutions, and the significant improvement in the rate of convergence is demonstrated.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/11934
Subject Headings: Strains and stresses, Photoelasticity, Numerical analysis--Data processing
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.
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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: Finite Element Modeling and Fatigue Analysis of Composite Turbine Blades under Random Ocean Current and Turbulence.
Creator: Canino, Marco M., Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Several modifications have been implemented to numerical simulation codes based on blade element momentum theory (BEMT), for application to the design of ocean current turbine (OCT) blades. The modifications were applied in terms of section modulus and include adjustments due to core inclusion, buoyancy, and added mass. Hydrodynamic loads and mode shapes were calculated using the modified BEMT based analysis tools. A 3D model of the blade was developed using SolidWorks. The model was...
Show moreSeveral modifications have been implemented to numerical simulation codes based on blade element momentum theory (BEMT), for application to the design of ocean current turbine (OCT) blades. The modifications were applied in terms of section modulus and include adjustments due to core inclusion, buoyancy, and added mass. Hydrodynamic loads and mode shapes were calculated using the modified BEMT based analysis tools. A 3D model of the blade was developed using SolidWorks. The model was integrated with ANSYS and several loading scenarios, calculated from the modified simulation tools, were applied. A complete stress and failure analysis was then performed. Additionally, the rainflow counting method was used on ocean current velocity data to determine the loading histogram for fatigue analysis. A constant life diagram and cumulative fatigue damage model were used to predict the OCT blade life. Due to a critical area of fatigue failure being found in the blade adhesive joint, a statistical analysis was performed on experimental adhesive joint data.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004727, http://purl.flvc.org/fau/fd/FA00004727
Subject Headings: Composite materials -- Fatigue, Finite element method, Fluid dynamics, Marine turbines -- Mathematical models, Ocean wave power, Structural dynamics
Format: Document (PDF)

Title: Enhancing Fracture Toughness and Thermo-Mechanical Properties of Vinyl-ester Composites Using a Hybrid Inclusion of CNT and GNP.
Creator: Gapstur, Christopher M., Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: We report a method of increasing fracture toughness (KIc) and strain energy release rate (GIc) of vinyl-ester (VE) matrix by adopting a hybrid (dual) reinforcement strategy. The idea of using this strategy was to trigger intrinsic polymer-nanoparticle interaction such as carbon nanotube (CNT) pull-out and interface sliding to enhance energy absorption during fracture. Additionally, we included a second reinforcement, graphene nanoplatelets (GNP), to promote crack-deflection, crack bridging...
Show moreWe report a method of increasing fracture toughness (KIc) and strain energy release rate (GIc) of vinyl-ester (VE) matrix by adopting a hybrid (dual) reinforcement strategy. The idea of using this strategy was to trigger intrinsic polymer-nanoparticle interaction such as carbon nanotube (CNT) pull-out and interface sliding to enhance energy absorption during fracture. Additionally, we included a second reinforcement, graphene nanoplatelets (GNP), to promote crack-deflection, crack bridging and cross-linking density. Both reinforcements were dispersed into the polymer in three states: non-functionalized (nf>); functionalized with COOH (f>); surface-treated with Triton X-100 (TX100). We embarked on numerous experiments with many combinations of these variables. We measured KIc and GIc using ASTM D5045-14. We conducted an exhaustive iterative investigation with three systems (f>CNT-VE; f>GNP-VE; f>CNT-f>GNP-VE) to determine the best weight-percentage for the nanocomposite system that produced the highest KIc and GIc values when compared to neat-VE. We found that 0.5wt% f>CNT with 0.25wt% f>GNP in the VE matrix resulted in the highest fracture toughness values and was termed the optimized hybrid nanocomposites (OHN) system. Subsequently, we explored further increasing the KIc and GIc of OHN through altering the nanoparticle surface characteristics, which led to four OHN groups: f>CNT-f>GNP-VE; f>CNT-f>GNP-TX100-VE; nf>CNT-nf>GNP-TX100-VE; nf>CNT-nf>GNP-VE. We discovered that the OHN group with non-functionalized nanofillers that were TX100 surface treated (0.5wt%nf>CNT-0.25wt%nf>GNP-TX100-VE) generated the greatest improvements in KIc and GIc. Ultimately, we observed that the KIc of neat-VE increased by 65%, from 1.14 to 1.88 MPa*(m½). The improvement in GIc was even greater with an increase of 166%, from 370 to 985 J/(m2). Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) studies showed a minor shift in glass transition temperature (Tg) by up to 8°C when comparing neat-VE specimens to OHN specimens. A similar increase in maximum thermal decomposition temperature (Tp) of up to 8°C was observed through thermogravimetric analysis (TGA) and derivative TGA (DTG). Scanning electron microscope (SEM) studies revealed that the source of improvements in fracture toughness and thermal properties was primarily the three-dimensional hybrid nanostructures (3DHN) that formed by binding CNT and GNP together, which caused an increase in nanoparticle surface area and inhibited agglomerations.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013062
Subject Headings: Carbon nanotubes., Graphene., Vinyl ester resins.
Format: Document (PDF)

Title: Design and analysis of hybrid titanium-composite hull structures under extreme wave and slamming loads.
Creator: Rahman, Md Hafizur, Mahfuz, Hassan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A finite element tool has been developed to design and investigate a multi-hull composite ship structure, and a hybrid hull of identical length and beam. Hybrid hull structure is assembled by Titanium alloy (Ti-6Al-4V) frame and sandwich composite panels. Wave loads and slamming loads acting on both hull structures have been calculated according to ABS rules at sea state 5 with a ship velocity of 40 knots. Comparisons of deformations and stresses between two sets of loadings demonstrate that...
Show moreA finite element tool has been developed to design and investigate a multi-hull composite ship structure, and a hybrid hull of identical length and beam. Hybrid hull structure is assembled by Titanium alloy (Ti-6Al-4V) frame and sandwich composite panels. Wave loads and slamming loads acting on both hull structures have been calculated according to ABS rules at sea state 5 with a ship velocity of 40 knots. Comparisons of deformations and stresses between two sets of loadings demonstrate that slamming loads have more detrimental effects on ship structure. Deformation under slamming is almost one order higher than that caused by wave loads. Also, Titanium frame in hybrid hull significantly reduces both deformation and stresses when compared to composite hull due to enhancement of in plane strength and stiffness of the hull. A 73m long hybrid hull has also been investigated under wave and slamming loads in time domain for dynamic analysis.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004048
Subject Headings: Hulls (Naval architecture) -- Design and construction, Ships -- United States -- Design and construction, Structural dynamics, Water waves -- Mathematical models
Format: Document (PDF)

Title: Effects of Carbon Nanotube (CNT) Dispersion and Interface Condition on Thermo-Mechanical Behavior of CNT-Reinforced Vinyl Ester.
Creator: Sabet, Seyed Morteza, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In fabrication of nanoparticle-reinforced polymers, two critical factors need to be taken into account to control properties of the final product; nanoparticle dispersion/distribution in the matrix; and interfacial interactions between nanoparticles and their surrounding matrix. The focus of this thesis was to examine the role of these two factors through experimental methodologies and molecular-level simulations. Carbon nanotubes (CNTs) and vinyl ester (VE) resin were used as nanoparticles...
Show moreIn fabrication of nanoparticle-reinforced polymers, two critical factors need to be taken into account to control properties of the final product; nanoparticle dispersion/distribution in the matrix; and interfacial interactions between nanoparticles and their surrounding matrix. The focus of this thesis was to examine the role of these two factors through experimental methodologies and molecular-level simulations. Carbon nanotubes (CNTs) and vinyl ester (VE) resin were used as nanoparticles and matrix, respectively. In a parametric study, a series of CNT/VE nanocomposites with different CNT dispersion conditions were fabricated using the ultrasonication mixing method. Thermomechanical properties of nanocomposites and quality of CNT dispersion were evaluated. By correlation between nanocomposite behavior and CNT dispersion, a thermomechanical model was suggested; at a certain threshold level of sonication energy, CNT dispersion would be optimal and result in maximum enhancement in properties. This threshold energy level is also related to particle concentration. Sonication above this threshold level, leads to destruction of nanotubes and renders a negative effect on the properties of nanocomposites. In an attempt to examine the interface condition, a novel process was developed to modify CNT surface with polyhedral oligomeric silsesquioxane (POSS). In this process, a chemical reaction was allowed to occur between CNTs and POSS in the presence of an effective catalyst. The functionalized CNTs were characterized using TEM, SEM-EDS, AFM, TGA, FTIR and Raman spectroscopy techniques. Formation of amide bonds between POSS and nanotubes was established and verified. Surface modification of CNTs with POSS resulted in significant improvement in nanotube dispersion. In-depth SEM analysis revealed formation of a 3D network of well-dispersed CNTs with POSS connections to the polymer. In parallel, molecular dynamics simulation of CNT-POSS/VE system showed an effective load transfer from polymer chains to the CNT due to POSS linkages at the interface. The rigid and flexible network of CNTs is found to be responsible for enhancement in elastic modulus, strength, fracture toughness and glass transition temperature (Tg) of the final nanocomposites.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004628, http://purl.flvc.org/fau/fd/FA00004628
Subject Headings: Carbon nanotubes., Carbon composites., Polymeric composites., Fibrous composites, Nanostructured materials., Composite materials--Mechanical properties.
Format: Document (PDF)

Title: Investigation of Structure-Property Relationship of a High Temperature Polyimide Reinforced with Nanoparticles.
Creator: Rowbottom, Colin, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Nano-reinforced polymeric systems have demonstrated a great deal of interest within academia and industry, due to the intrinsic properties of the graphene nanofillers, having excellent mechanical, thermal and electrical properties. The reinforcement of multiwall carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were introduced into a low cost, non-carcinogenic, high temperature PMR type polyimide resin. The effects of the interfacial interaction and dispersion quality resulted in...
Show moreNano-reinforced polymeric systems have demonstrated a great deal of interest within academia and industry, due to the intrinsic properties of the graphene nanofillers, having excellent mechanical, thermal and electrical properties. The reinforcement of multiwall carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were introduced into a low cost, non-carcinogenic, high temperature PMR type polyimide resin. The effects of the interfacial interaction and dispersion quality resulted in improvement in the glass transition temperature (Tg), elastic modulus and thermal stability by, 31°C, 63% and 16°C, respectively. In fine, this study presents a simple but effective high temperature polyimide (HTPI) nanocomposites manufacturing procedure and established that nanoparticle reinforcement can be used to improve both thermal and mechanical properties.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013035
Subject Headings: Polyimides, Nanoparticles, Carbon nanotubes, Graphene
Format: Document (PDF)

Title: Studies of nanoparticle reinforced polymer coatings for trace gas detection.
Creator: Davis, Charles, Mahfuz, Hassan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: With the goal of improving chemical detection methods for buried improvised explosive devices (IED’s), the intention of this study is to show that functionalized nano-particles improve the sensing properties of a polymer applied to gas sensors. The approach was reinforcing the polymer, Nafion, with acid-functionalized carbon nanotubes (CNT’s). Ammonia was chosen as the analyte for its similarity to IED byproducts without the dangers of toxicity or explosion. Two sensor platforms were...
Show moreWith the goal of improving chemical detection methods for buried improvised explosive devices (IED’s), the intention of this study is to show that functionalized nano-particles improve the sensing properties of a polymer applied to gas sensors. The approach was reinforcing the polymer, Nafion, with acid-functionalized carbon nanotubes (CNT’s). Ammonia was chosen as the analyte for its similarity to IED byproducts without the dangers of toxicity or explosion. Two sensor platforms were investigated: Quartz crystal microbalances (QCM’s) and microcantilevers (MC’s). Preliminary evaluation of treated QCM’s, via frequency analyzer, showed improvements in sensitivity and fast reversal of adsorption; and suggested increased stability. Tests with coated MC’s also supported the findings of QCM tests. Amplitude response of MC’s was on average 4 times greater when the Nafion coating contained CNT’s. Quantitative QCM testing with gas-flow meters showed that with CNT inclusion: the average number of moles adsorbed increased by 35% (>1.2 times frequency response); sensitivity improved by 0.63 Hz/ppt on average; although the detection threshold decreased marginally; but reusability was much better after extended exposures to concentrated ammonia.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004014
Subject Headings: Conducting polymers, Detectors -- Technological innovations, Explosives -- Detection, Nanocomposites (Materials), Nanostructured materials, Smart materials
Format: Document (PDF)

Title: Effects of POSS Fiber Sizing on the Mechanical and Thermal Properties of CarbonNinyl Ester Composites.
Creator: Powell, Felicia M., Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The degradation of polymer composites in moist environments is a limiting factor in the advancement of composite technology. The key to mitigate this degradation is to maintain the integrity of the fiber/matrix (F/M) interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by treating the carbon fiber with polyhedral oligomeric silsesquioxane (POSS). Two POSS systems, namely octaisobutyl and trisilanolphenyl, have been investigated. A set of chemical and...
Show moreThe degradation of polymer composites in moist environments is a limiting factor in the advancement of composite technology. The key to mitigate this degradation is to maintain the integrity of the fiber/matrix (F/M) interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by treating the carbon fiber with polyhedral oligomeric silsesquioxane (POSS). Two POSS systems, namely octaisobutyl and trisilanolphenyl, have been investigated. A set of chemical and mechanical procedures has been developed to coat carbon fibers with POSS, and fabricate layered composites using vinyl ester resin. lnterlaminar shear, transverse tension, and low velocity impact tests on composites have indicated around 10-38% improvement in mechanical properties with respect to control samples. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) tests have also shown significant improvement in glass transition temperature (T9). Hygrothermal tests, under various environments, have demonstrated that POSS reduces water absorption by 20-30%.
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Date Issued: 2009
PURL: http://purl.flvc.org/fau/fd/FA00012540
Subject Headings: Surface chemistry, Composite materials--Biodegradation, Carbon compounds--Testing, Thermodynamics, Fibrous compounds--Testing
Format: Document (PDF)

Title: Nanoparticle Reinforced Core Materials for Sandwich Construction: Investigation of Mechanical and Fracture Behavior.
Creator: Stewart, Justin Keith, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Sandwich composites provide excellent structural integrity for a variety of applications. In this study pristine and functionalized 30 nrn Silicon Carbide nanoparticles are infused into a low density polyurethane foam used for the inner core of the sandwich structure. The mechanical properties are characterized using compressive, tensile, and flexural tests. A plane-strain fracture test and a TSD (Tilted Sandwich Debond) test characterize the fracture properties of the foam and the coreskin...
Show moreSandwich composites provide excellent structural integrity for a variety of applications. In this study pristine and functionalized 30 nrn Silicon Carbide nanoparticles are infused into a low density polyurethane foam used for the inner core of the sandwich structure. The mechanical properties are characterized using compressive, tensile, and flexural tests. A plane-strain fracture test and a TSD (Tilted Sandwich Debond) test characterize the fracture properties of the foam and the coreskin interface. Thermal characterization is carried out using Dynamic Mechanical Analysis (DMA) and Thermo-Gravimetric Analysis (TGA). FTIR spectral analysis reveals changes in molecular bonding due to pristine and functionalized nanoparticle infusion. The fracture resistance of the foam is improved and the delamination strength of the sandwich construction with nanophased cores is dramatically improved. The TSD testing indicated that the G1c value rose from 0.14 kJ/m^2 in the neat foam to 0.56 kJ/m^2 with just 0.1 wt% of SiC nanoparticle inclusion reflecting an enhancement of almost 300%.
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Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00012558
Subject Headings: Composite materials--Mechanical properties, Nanostructured materials--Testing, Fracture mechanics
Format: Document (PDF)

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