Current Search: Composite materials -- Testing (x)
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- Title
- Mode II interlaminar fracture toughness of interleaved composite materials.
- Creator
- Aksoy, Adnan., Florida Atlantic University, Carlsson, Leif A.
- Abstract/Description
-
Interlaminar mode II fracture toughness, GIIC, of thermoset and thermoplastic interleaved (TSI and TPI) composites were investigated over a wide range of interleaf thickness. TPI specimens had four to about seven times larger GIIC than those without an interleaf. Poor adhesion observed for some TPI specimens were likely to be due to contaminated film materials. Thermoset interleaves were less effective in enhancing the mode II fracture toughness. However, even 0.043 mm thermoset interleaves...
Show moreInterlaminar mode II fracture toughness, GIIC, of thermoset and thermoplastic interleaved (TSI and TPI) composites were investigated over a wide range of interleaf thickness. TPI specimens had four to about seven times larger GIIC than those without an interleaf. Poor adhesion observed for some TPI specimens were likely to be due to contaminated film materials. Thermoset interleaves were less effective in enhancing the mode II fracture toughness. However, even 0.043 mm thermoset interleaves gave three times larger G$\sb{\rm IIC}$ than those without an interleaf. Estimates of the volume of the yielded material around the crack tip based on a quasi-elastic finite element approach and Irwin's model showed that the yield zone height reaches a peak value for increasing interleaf thickness for both TSI and TPI specimens. Furthermore, fracture toughness data correlates well with yield zone heights.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14594
- Subject Headings
- Composite materials--Cracking, Fracture mechanics, Composite materials--Testing
- Format
- Document (PDF)
- Title
- A study of the effects of nanoparticle modification on the thermal, mechanical and hygrothermal performance of carbon/vinyl ester compounds.
- Creator
- Powell, Felicia M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Enhancement of mechanical, thermal and hygrothermal properties of carbon fiber/vinyl ester (CFVE) composites through nanoparticle reinforcement has been investigated. CFVE composites are becoming more and more attractive for marine applications due to two reasons : high specific strength and modulus of carbon fiber and low vulnerability of vinyl ester resin to sea water. However, the problem with this composite system is that the fiber matrix (F/M) interface is inherently weak. This leads to...
Show moreEnhancement of mechanical, thermal and hygrothermal properties of carbon fiber/vinyl ester (CFVE) composites through nanoparticle reinforcement has been investigated. CFVE composites are becoming more and more attractive for marine applications due to two reasons : high specific strength and modulus of carbon fiber and low vulnerability of vinyl ester resin to sea water. However, the problem with this composite system is that the fiber matrix (F/M) interface is inherently weak. This leads to poor mechanical properties and fast ingress of water at the interface further deteriorating the properties. This investigation attempts to address these deficiencies by inclusion of nanoparticles in CFVE composites. Three routes of nanoparticle reinforcement have been considered : nanoparticle coating of the carbon fiber, dispersion of nanoparticles in the vinyl ester matrix, and nanoparticle modification of both the fiber and the matrix. Flexural, short beam shear and tensile testing was conducted after exposure to dry and wet environments. Differential scanning calorimetry and dynamic mechanical analysis were conducted as well. Mechanical and thermal tests show that single inclusion of nanoparticles on the fiber or in the matrix increases carbon/vinyl ester composite properties by 11-35%. However, when both fiber and matrix were modified with nanoparticles, there was a loss of properties.
Show less - Date Issued
- 2012
- PURL
- http://purl.flvc.org/FAU/3352286
- Subject Headings
- Composite materials, Mechanical properties, Nanostructured materials, Testing, Carbon compounds, Testing, Fibrous composites, Testing, Surface chemistry
- Format
- Document (PDF)
- Title
- Determination of the tensile strength of the fiber/matrix interface for glass/epoxy & carbon/vinylester.
- Creator
- Totten, Kyle, Carlsson, Leif A., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The tensile strength of the fiber/matrix interface was determined through the development of an innovativetest procedure.Aminiature tensile coupon with a through-thickness oriented, embedded single fiberwas designed. Tensile testing was conducted ina scanning electron microscope (SEM)while the failure process could be observed.Finite element stress analysis was conducted to determine the state of stressat the fiber/matrix interface in the tensile loaded specimen, and the strength of the...
Show moreThe tensile strength of the fiber/matrix interface was determined through the development of an innovativetest procedure.Aminiature tensile coupon with a through-thickness oriented, embedded single fiberwas designed. Tensile testing was conducted ina scanning electron microscope (SEM)while the failure process could be observed.Finite element stress analysis was conducted to determine the state of stressat the fiber/matrix interface in the tensile loaded specimen, and the strength of the interface.Test specimensconsistingof dry E-glass/epoxy and dry and seawater saturatedcarbon/vinylester510Awere preparedand tested.The load at the onset of debondingwascombined withthe radial stressdistributionnear thefree surface of the specimento reducethe interfacial tensile strength. For glass/epoxy, was 36.7±8.8MPa.For the dryand seawater saturated carbon/vinylester specimensthetensilestrengthsof the interface were 23.0±6.6 and 25.2±4.1MPa, respectively.The difference is not significant.
Show less - Date Issued
- 2015
- PURL
- http://purl.flvc.org/fau/fd/FA00004415, http://purl.flvc.org/fau/fd/FA00004415
- Subject Headings
- Composite materials -- Mechanical properties, Composite materials -- Testing, Fibrous composites -- Mechanical properties, Polymeric composites -- Mechanical properties, Viscoelasticity
- Format
- Document (PDF)
- Title
- Interlaminar mode III fracture ECT method - testing and analysis.
- Creator
- Browning, Grant., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
In an effort to obtain an improved mode III fracture toughness test suitable for a testing standard, mechanics analysis, experimental testing, and finite element analysis (FEA) have been conducted. Of particular concern are the merits of one-point and two-point edge crack torsion (ECT) test methods, the influence of specimen geometry that overhangs beyond load/support points, and the influence of crack length on the compliance and energy release rate. Shear stress distributions at the crack...
Show moreIn an effort to obtain an improved mode III fracture toughness test suitable for a testing standard, mechanics analysis, experimental testing, and finite element analysis (FEA) have been conducted. Of particular concern are the merits of one-point and two-point edge crack torsion (ECT) test methods, the influence of specimen geometry that overhangs beyond load/support points, and the influence of crack length on the compliance and energy release rate. Shear stress distributions at the crack front are determined to examine the uniformity of mode III loading and mode II influence. The shear stress distributions in the one-point and two-point tests are virtually identical, indicating that either of the two tests could be used interchangeably. Based on the uniformity of the mode III shear stress distribution along the crack front, it was found that the ECT specimen should have minimum overhang. Longer crack lengths tend to produce nonuniform shear stress distributions. A modified two-point ECT test fixture was developed to allow testing of specimens with a range of dimensions. This development enabled experimental verification of the results from the FEA overhang series. The specimens with a minimum overhang produced consistant mode III toughness data. The most reliable way to reduce data is through the original compliance calibration method. A modified ECT specimen was developed with a staggered crack front to produce uniform mode III crack growth. Finite element analysis of the modified ECT specimen shows a uniform mode III stress distribution along the crack front with little mode II interaction.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/187206
- Subject Headings
- Laminated materials, Testing, Fracture mechanics, Strength of materials, Testing, Composite materials, Testing
- 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
- Evaluation of Water Degradation ofPolymer Matrix Composites by Micromechanical and Macromechanical Tests.
- Creator
- Ramirez, Felipe A., Carlsson, Leif A., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Degradation of the critical components of polymer matrix composites in marine environments had been experimentally investigated. Water absorption behavior of neat resin and composite specimens was examined. The tensile strength of fibers was monitored using the single filament test. The mechanical properties of the resins were monitored by tensile, flexure, and dynamic-mechanical tests. In addition, matrix shrinkage during cure and matrix swelling after immersion in water were monitored. The...
Show moreDegradation of the critical components of polymer matrix composites in marine environments had been experimentally investigated. Water absorption behavior of neat resin and composite specimens was examined. The tensile strength of fibers was monitored using the single filament test. The mechanical properties of the resins were monitored by tensile, flexure, and dynamic-mechanical tests. In addition, matrix shrinkage during cure and matrix swelling after immersion in water were monitored. The integrity of the fiber/matrix (F/M) interface of the composite systems was studied using the single fiber fragmentation test (SFFT). Macroscopic composites were examined using transverse tensile and transverse flexure tests to study the influence of the integrity of the matrix and F/M interface on the macroscopic response. In addition, for characterization of F/M debonding in the SFFT, a fracture mechanics model and modified test procedure were developed.
Show less - Date Issued
- 2008
- PURL
- http://purl.flvc.org/fau/fd/FA00012543
- Subject Headings
- Composite materials--Mechanical properties, Polymeric composites--Testing, Fibrous composites--Testing, Polymers--Deterioration
- 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%.
Show less - 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)
- Title
- The effects of nitric acid and silane surface treatments on carbon fibers and carbon/vinyl ester composites before and after seawater exposure.
- Creator
- Langston, Tye A., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface...
Show moreThis research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion., Their composites displayed poor wetting, high void content, high seawater weight gain, and low swelling. Both fiber treatment types resulted in great improvements in dry transverse tensile strength over the untreated fibers, but the oxidized fiber composites lost strength as the acid treatment time was extended, due to poor wetting. The acid/silane treated composites lost some transverse tensile strength after seawater exposure, but the nitric acid oxidized fiber composites appeared to be more seawater durable.
Show less - Date Issued
- 2008
- PURL
- http://purl.flvc.org/FAU/172669
- Subject Headings
- Silane compounds, Testing, Surface chemistry, Composite materials, Biodegradation, Carbon compounds, Testing
- Format
- Document (PDF)
- Title
- Chemical Method and Device to Detect Underwater Trace Explosives via Photo-Luminescence.
- Creator
- Langston, Tye A., Florida Atlantic University, Granata, Richard D., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This research tests the use of sensitized lanthanide ions to determine if they can detect water-borne explosive traces and produces two designs for a field-deployable underwater explosive trace detector. 1,1 0-phenanthroline and thenoyltritluoroacetone are evaluated as sensitizing ligands to absorb energy and initiate the fluorescence process in europium ions. Different compounds obtained via ligand choice and mixing order are evaluated for their ability to produce a large fluorescence...
Show moreThis research tests the use of sensitized lanthanide ions to determine if they can detect water-borne explosive traces and produces two designs for a field-deployable underwater explosive trace detector. 1,1 0-phenanthroline and thenoyltritluoroacetone are evaluated as sensitizing ligands to absorb energy and initiate the fluorescence process in europium ions. Different compounds obtained via ligand choice and mixing order are evaluated for their ability to produce a large fluorescence differential between explosive-laden and explosive-absent solutions. Optimal excitation and emission wavelengths for several different compounds are determined, as well as practical wavelengths to be applied in the field. The effect of methanol as a solvent to deliver the reagents is evaluated and rough solubility limits are determined. The effects of seawater constituents on detection are investigated and explosive detection limits are determined. It was found that this method and device are viable for underwater explosive trace detection. A field-deployable device is designed, characterized, and proven.
Show less - Date Issued
- 2006
- PURL
- http://purl.flvc.org/fau/fd/FA00012600
- Subject Headings
- Silane compounds--Testing, Surface chemistry, Composite materials--Biodegradation, Carbon compounds--Testing
- 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%.
Show less - 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)