In the long term development of the research on wind waves and their modelling, in particular of the inner and coastal seas, the present situation is framed with a short look at the past, a critical analysis of the present capabilities and a foresight of where the field is likely to go. After a short introduction, Chapter 2 deals with the basic processes at work and their modelling aspects. Chapter 3 highlights the interaction with wind and currents. Chapter 4 stresses the need for a more complete, spectral, approach in data assimilation. Chapter 5 summarizes the situation with a discussion on the present status in wave modelling and a look at what we can expect in the future.

Accurate estimation of storm surge along the coasts subject to extreme storm conditions requires proper wind and pressure forcing and quantification of the wind waves resulting from local and far-field energy sources. This paper summarizes the steps involved in accurately representing the offshore wave climate for the North Atlantic Coast Comprehensive Study (NACCS) domain, defined from the United States-Canadian border in Maine to the Virginia-North Carolina border. The motivation of the regional wave modeling is to provide offshore boundary conditions for the simulation of extreme extratropical and synthetic tropical events to drive the nearshore wave and surge modeling efforts within the NACCS. The offshore wave conditions were estimated using the third-generation WAve Modelling (WAM) model. Value-added wind fields were defined for each of the four wave model grids (North Atlantic Ocean Basin, U.S. Coastal Regional scale, and two subregional-scale grid systems covering the NACCS coastal domain). Five tropical events (Hurricanes Sandy, Irene, Isabel, and Gloria and Tropical Storm Josephine) and 17 extratropical events were simulated to evaluate WAM's performance. Model results were compared with 30 point-source measurements available during these storm events. Time, scatter, and quartile-quartile plots; Taylor diagrams; and a battery of statistical tests were used in the evaluation process. The WAM provided quality zero-moment wave height estimates, with biases in the range of -0.07 to -0.14 m, RMS errors (RMSEs) of about 0.40 m, scatter indexes (SIs) around 25%, and a correlation of 0.95 compared with the measurements. The wave period results contained the greatest errors with peak period biases of -0.26 to 0.06 s, RMSEs from 2.4 to 2.7 s, SIs near 25%, and a correlation between 0.47 and 0.59. The mean period biases were about -0.70s, RMSEs were about 1.5 s, and there was a correlation of 0.6-0.7. The mean wave direction biases ranged from 4.5 to -0.34 degrees with RMSEs of 55 degrees.

Point-source wave measurements have and continue to be an important element in assessing the wave conditions, aiding the Weather Prediction Center’s evaluations of their forecast, used in data assimilation, wave modeling investigations, used in algorithms estimating waves from satellite-based altimeters, climate studies, wave energy resource assessments and other applications. The work presented here assesses the similarities/differences between various sensor/payload packages housed in a 6N NOMAD buoy that is deployed in Monterey Canyon as part of the Buoy Farm, and a comprehensive intrameasurement evaluation.

The effect of fiber sizing and surface texture on the strength and energy absorbing capacity of fiber reinforced composites has been evaluated at two length scales using the macromechanical quasi-static punch shear test and the micromechanical microdroplet test methods. E-Glass/SC-79 epoxy composite laminates with four different fiber sizing formulations with various degrees of chemical bonding and surface texture have been investigated. The failure modes during perforation and different energy dissipating damage mechanisms were identified and quantified. The punch shear strength and the total energy absorption per unit volume of composite with hybrid sizing have increased by 48% and 100% over the incompatible sizing. These results showed linear correlations with the interphase properties reported earlier by the authors (Gao et al., 2011) and provided a methodology for developing new sizing by tailoring chemical bonding and the fiber surface texture at the fiber–matrix interphase for improving both strength and energy absorption of composites.

Multifunctional siloxane copolymers with terminal vinyl or allyl functional groups are synthesised through the borane-catalysed polycondensation of hydrosilanes and alkoxysilanes. Copolymers of varying molecular weights ((M) over bar (w) = 13200-70 300 g mol(-1)), spatially well-distributed functional groups and high end-group fidelity are obtained in a facile and robust synthetic scheme involving polycondensation, end-group transformation and different functionalisation reactions such as Cu(I)-mediated azide-alkyne cycloaddition. Pendant alkyl chloride, alkyl azide, bromoisobutyryl, 4-nitrobenzene and 1-ethyl-imidazolium chloride fragments with programmable spatial distributions are incorporated in the copolymer backbones. NMR and FTIR spectroscopy as well as size exclusion chromatography corroborate the efficacy and versatility of this modular approach.

Hurricane Ike (2008) made landfall near Galveston, Texas, as a moderate intensity storm. Its large wind field in conjunction with the Louisiana-Texas coastline's broad shelf and large scale concave geometry generated waves and surge that impacted over 1000 km of coastline. Ike's complex and varied wave and surge response physics included: the capture of surge by the protruding Mississippi River Delta; the strong influence of wave radiation stress gradients on the Delta adjacent to the shelf break; the development of strong wind driven shore-parallel currents and the associated geostrophic setup; the forced early rise of water in coastal bays and lakes facilitating inland surge penetration; the propagation of a free wave along the southern Texas shelf; shore-normal peak wind-driven surge; and resonant and reflected long waves across a wide continental shelf. Preexisting and rapidly deployed instrumentation provided the most comprehensive hurricane response data of any previous hurricane. More than 94 wave parameter time histories, 523 water level time histories, and 206 high water marks were collected throughout the Gulf in deep water, along the nearshore, and up to 65 km inland. Ike's highly varied physics were simulated using SWAN?+?ADCIRC, a tightly coupled wave and circulation model, on SL18TX33, a new unstructured mesh of the Gulf of Mexico, Caribbean Sea, and western Atlantic Ocean with high resolution of the Gulf's coastal floodplain from Alabama to the Texas-Mexico border. A comprehensive validation was made of the model's ability to capture the varied physics in the system.

Covalent attachment of pre-formed nanosilica particles to the surface of ultra-high molecular weight polyethylene (UHMWPE) was attained through a grafting reaction using 3-glycidoxypropyltrimethoxysilane (GPS) once the surface had been exposed to a plasma treatment. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements showed a change in both the morphology and composition of the surface with the appearance of micro-depressions, grafting of oxygen containing functional groups, and improved wettability upon exposure to the plasma. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and Rutherford backscattering spectrometry (RBS) confirmed that plasma activation and a silane intermediary were required for the efficient chemical grafting of the nanosilica. Attempts at grafting the nanosilica to as-received polyethylene films proved unsuccessful due to the absence of covalent bonding sites.

Hurricane Gustav (2008) made landfall in southern Louisiana on 1 September 2008 with its eye never closer than 75 km to New Orleans, but its waves and storm surge threatened to flood the city. Easterly tropical-storm-strength winds impacted the region east of the Mississippi River for 12-15 h, allowing for early surge to develop up to 3.5 m there and enter the river and the city's navigation canals. During landfall, winds shifted from easterly to southerly, resulting in late surge development and propagation over more than 70 km of marshes on the river's west bank, over more than 40 km of Caernarvon marsh on the east bank, and into Lake Pontchartrain to the north. Wind waves with estimated significant heights of 15 m developed in the deep Gulf of Mexico but were reduced in size once they reached the continental shelf. The barrier islands further dissipated the waves, and locally generated seas existed behind these effective breaking zones.The hardening and innovative deployment of gauges since Hurricane Katrina (2005) resulted in a wealth of measured data for Gustav. A total of 39 wind wave time histories, 362 water level time histories, and 82 high water marks were available to describe the event. Computational models-including a structured-mesh deepwater wave model (WAM) and a nearshore steady-state wave (STWAVE) model, as well as an unstructured-mesh "simulating waves nearshore'' (SWAN) wave model and an advanced circulation (ADCIRC) model-resolve the region with unprecedented levels of detail, with an unstructured mesh spacing of 100-200 m in the wave-breaking zones and 20-50 m in the small-scale channels. Data-assimilated winds were applied using NOAA's Hurricane Research Division Wind Analysis System (H*Wind) and Interactive Objective Kinematic Analysis (IOKA) procedures. Wave and surge computations from these models are validated comprehensively at the measurement locations ranging from the deep Gulf of Mexico and along the coast to the rivers and floodplains of southern Louisiana and are described and quantified within the context of the evolution of the storm.

Polymer–polymer composites comprised of vinyl ester matrices (VE) and polypropylene (PP) fiber meshes were fabricated and tested in this investigation. Results indicated that PP fibers greatly enhanced fracture toughness; however, strength of the VE was significantly reduced as voids were observed at the interface of the PP and VE. A two-step surface modification, oxygen plasma treatment followed by grafting vinyltrimethoxysilane (VTMS), was conducted on PP fibers in an effort to improve interfacial strength. Interfacial discontinuities of composites were improved after surface modification of PP. The oxygen plasma treatment added hydrophilic functional groups but caused surface roughness. Surface treatment of PP slightly increased fracture toughness of the PP-VE composite by enhancing energy absorption capacity at the interface. However, mechanical strength and modulus did not significantly increase for the composite using VTMS grafted PP fibers due to the weak fiber material. Small PP fibers with higher strength may attain the expected improvement in mechanical properties after surface treatment.

The unstructured-mesh SWAN spectral wave model and the ADCIRC shallow-water circulation model have been integrated into a tightly-coupled SWAN + ADCIRC model. The model components are applied to an identical, unstructured mesh; share parallel computing infrastructure; and run sequentially in time. Wind speeds, water levels, currents and radiation stress gradients are vertex-based, and therefore can be passed through memory or cache to each model component. Parallel simulations based on domain decomposition utilize identical sub-meshes, and the communication is highly localized. Inter-model communication is intra-core, while intra-model communication is inter-core but is local and efficient because it is solely on adjacent sub-mesh edges. The resulting integrated SWAN + ADCIRC system is highly scalable and allows for localized increases in resolution without the complexity or cost of nested meshes or global interpolation between heterogeneous meshes. Hurricane waves and storm surge are validated for Hurricanes Katrina and Rita, demonstrating the importance of inclusion of the wave-circulation interactions, and efficient performance is demonstrated to 3062 computational cores.

Prior research has demonstrated that fiber-sizings can be designed to yield composite materials that simultaneously possess high energy absorption and structural properties. The improved mechanical properties resulted from control of the fiber surface chemistry and nano-scale topological features within the fiber–matrix interphase. The present study further explains the role of sizing chemistry and surface roughness on composite material performance. Model and commercial glass fiber epoxy specimens were fabricated using these fiber sizing systems resulting in interphase regions with varied surface topology and chemical functionality. Micromechanical measurements were performed using the microdroplet adhesion test method to quantify the fiber–matrix interfacial properties. Improvement in energy absorption and interfacial shear strength due to the presence of the nano-scale silica were quantified. Inspection of the failure modes revealed that the existence of colloidal silica promotes crack propagation along a more tortuous path within the interphase that results in progressive failure and contributes to increased energy dissipation.

Most of the research to date has focused on tailoring the interphase adhesion by controlling the degree of chemical bonding between fiber and resin. The interfacial shear strength (IFSS) has been increased as much as 40% by modified chemical surface bonding [1-3]. However, it is well known that increasing the interfacial strength of the fiber reinforced polymeric composite material often leads to a reduction in the fracture toughness and vice versa [4-12]. In this study, the effects of mechanical interlocking, in addition to chemical bonding on the strength and energy absorption of glass fiber/epoxy interphase, were studied by creating texture on the fiber surface through the phase separation of silane blends. A series of tetraethoxysilane (TEOS)/3-glycidoxypropyltrimethoxysilane (GPS) blends in solutions of ethanol and water was selected to treat the glass fiber surface. The fiber coated with different surface treatments shows the change in fiber surface morphology due to the addition of TEOS. X-ray photoelectron spectroscopy (XPS) analysis showed that the GPS preferentially migrates to the coating surface which suggests that phase separation induced by the silane blend was the primary mechanism for the texture formation. Atomic force microscopy (AFM) was used to scan the fiber surface after the coating and the fiber surface texture was quantified by the roughness values. In addition, a single-fiber Microdroplet shear test was conducted to assess the interfacial properties between the textured glass surface and an epoxy matrix. Traditionally, interfacial shear strength is the only quantity that was determined from the load vs. displacement curve after microdroplet test. In this study, a new data-reduction scheme was developed to determine the energy absorption due to different failure mechanisms by taking into consideration both machine compliance and fiber stretching in the energy calculation. The results show as much as a three-fold increase in specific sliding energy absorption without sacrificing interfacial shear strength. The examination of failure surfaces shows that failure mode propagates through the textured interphase in a more tortuous path, which results in greater degree of energy absorption during fiber-matrix pullout. This study shows the potential for using chemical bonding and mechanical interlocking effects to improve both strength and energy absorption in fiber reinforced composites.

A model epoxy-silane interpenetrating network (IPN) was synthesized to simulate the molecular structure found at the fiber-matrix interphase. The Young's modulus (E) of the epoxy-silane IPN was determined through micromechanical analysis both quasi-statically and in the frequency domain. The epoxy-silane IPN was synthesized by diffusion of uncured diglycidyl ether of bisphenol A (DGEBA) epoxy resin and bis (p-aminocyclohexyl) methane (PACM) curing agent into spherical particles of condensed and crosslinked 3-glycidoxypropyltrimethoxysilane (GPS). This IPN composition was chosen to simulate the typical properties of a silane modified interphase found in glass reinforced composites. Differential scanning calorimetry (DSC) showed that the glass transition temperature (Tg) of the initial crosslinked siloxane network increases upon cure of the DGEBA and PACM, but was still significantly lower than that of the neat epoxy matrix. Additionally, dynamic mechanical analysis (DMA) was used in conjunction with the micromechanical C-Combining Rule to show that the Young's modulus of the epoxy-silane IPN spherical inclusions (Ei) is decreased in comparison to the Young's modulus of the matrix epoxy (Em) at all temperatures. The time-temperature superposition (tTsp) principle was successfully applied to the epoxy-silane IPN to determine viscoelastic properties at high frequencies. The viscoelastic properties of the epoxy-silane IPN may have implications with respect to the ballistic impact resistance of composite structures used for Army applications.

Abstract : The overall goal of this paper was to determine which factors of silane/silica chemistry most influenced surface coverage and surface roughness of glass surfaces. Nanotexturing of glass fibers has shown the potential to improve impact properties of glass reinforced composites. Previous work by Army researches determined that modifying fiber surfaces using a mixture of silane coupling agents that were both reactive and non-reactive towards the matrix phase, in conjunction with nanoscale colloidal silica, yielded a simultaneously high strength and tough composite. The focus of this work was to ascertain which factors of the silane and silica treatments were most influential in controlling the silica deposition on solid surfaces. The basis of the silane chemistry involves controlling the number of amine-functional groups on the fiber surface. Propyltrimethoxylsilane (PTMO) and aminopropyltrimethoxysilane (APS) are silanes that contain a propyl group and a primary amine, respectively. By varying the ratio of these silanes in solution, the concentration of amine groups on the fiber surface can be controlled. The amine groups on the fiber surface act as potential sites for epoxy-amine reactions. Two routes were chosen for affixing silica to the surface using the amine groups. In the first route, a reverse silane reaction is carried out; where the epoxy groups of a non-hydrolyzed glycidylpropyltrimethoxysilane (GPS) react with surface amine groups. Upon hydrolysis, the methoxy groups of the silane are converted to hydroxyl groups that undergo a condensation reaction with the silica. The second route for silica deposition involves the functionalization of the silica. In a separate step, hydrolyzed GPS is reacted with the silica to yield epoxy-functional silica. The epoxy groups on the silica can react with the amine groups on the glass surface.

Achieving high impact energy absorption without loss of structural performance in a glass fiber-reinforced composite can be obtained through a “materials by design” approach of the fiber matrix interphase through modification of current commercially formulated silane-based fiber sizing packages. In this paper, we document our attempt to balance the structural and impact performance of glass-reinforced composites produced using a fiber-sizing package composed of mixed silane coupling agents to vary the reactivity of the fiber with the matrix phase. Additionally, enhancement of post-failure energy absorption through increased frictional dissipation during fiber–matrix pull-out was explored through control of the surface roughness of the glass fibers. A unique inorganic–organic hybrid fiber sizing formulation was successfully applied at a commercial E-glass manufacturing facility to produce rovings as well as woven fabric reinforcements. Composite materials were manufactured using these specialized fabrics and the preliminary structural and impact energy responses of these materials have been measured.

Abstract : To meet the weight and performance goals of emerging Army Future Combat Systems. lightweight glass reinforced polymer (GRP) composite materials have been proposed as candidate materials to meet structural and ballistic performance requirements. During manufacture of the glass fibers a thin coating is applied for protection as well as control of performance in composite articles. Conventional glass-fiber coatings (sizings) use organofunctional molecules known as silane coupling agents to enhance the adhesion between the glass fiber reinforcement and the polymeric matrix and to increase the durability of the composite. For industrial glass fiber manufacturing the silane-coupling agent is applied as one of the constituents in a multicomponent fiber sizing package formulation during the initial stages of production. Sizings are essential to the processing and performance of advanced composite materials, yet they are poorly understood. For example, existing sizings are not optimized to simultaneously tailor the static and dynamic response of composite materials. Yet, it has been recognized that these sizings affect structural durability, impact resistance, and damage tolerance of fiber-reinforced composites. Published research indicates that the impact response of a GRP can be tailored for high- energy absorption by designing weak fiber-matrix interfacial interactions. Conversely structural performance (strength) is achieved by strong fiber-matrix interfacial interactions. Hence, the aforementioned trade- offs exist. Although the achievement of simultaneous high strength and energy absorption levels is desirable, the technology has not been available. New approaches are now available to overcome these traditional materials shortcomings.

Abstract : A series of hyperbranched materials have been developed that allow for the transportation of desired functional groups to the surface of a polymer blend by simple solution casting techniques. These materials have been employed to transport polyoxometalates, or POMs, to the surface of a polyurethane- polyether copolymer film. providing for a 10x increase in POM concentration at the surface compared to the bulk. The films were evaluated using x-ray photoelectron spectroscopy (XPS) and contact angle analysis, and their surface chemistry was dominated by the hyperbranched polymer incorporated into the blend.

The mechanical and viscoelastic properties of unidirectional vinyl-ester carbon fiber composites were investigated. A cooperativity analysis of the composites was performed on storage (E′) and loss modulus (E″) master curves obtained from dynamic mechanical analysis. The temperature sensitivity of the horizontal logarithmic shift factors (logaT), cooperativity, obtained from E′ data, was found to vary with the sizing used to pretreat the carbon fibers. The observed variations in the experimental trends in cooperativity with fiber sizing for the composite materials were found to deviate significantly from theory. However, the trends in tensile and apparent shear strength of the composites matched the observed qualitative trends in viscoelastic cooperativity obtained from the storage modulus master curves. These results may suggest that the viscoelastic and ultimate mechanical properties of a composite material are related. However, several inconsistencies were observed when comparing the E″ and E′ data which should also be considered in the interpretation of the experimental results.

The structure and properties of copolymerized sequential-interpenetrating networks (SeqIPNs) synthesized from amine-cured epoxies and free-radical polymerized dimethacrylates were examined. Materials were synthesized with and without the incorporation of an epoxy-terminated butadiene-nitrile reactive elastomer. Synthesis proceeded through full thermal cure of the epoxy-amine network, followed by polymerization of the methacrylate network. The methacrylate reactions were free-radically induced using thermal (peroxide-initiated) or photochemical [electron-beam (e-beam)] techniques. Fourier transform infrared spectroscopy was used to monitor epoxy-amine step-growth polymerization in situ and to measure final cure conversion of methacrylates. Structural examination of the IPNs using atomic force microscopy and scanning electron microscopy revealed microphase separation in the neat-SeqIPN materials and macroscopic phase separation of rubber-rich domains for elastomer-modified networks. Dynamic mechanical analysis of the SeqIPN determined that the properties of the network are strongly dependent on the cure conditions. Furthermore, the viscoelastic behavior of the e-beam-cured SeqIPN could be adequately described by the Williams-Landel-Ferry and Kohrausch-Willams-Watts equations, presumably because of a strong coupling between the epoxy-amine and methacrylate networks. (C) 2001 John Wiley & Sons, Inc.