Degradation of the Carbon Fiber/Vinylester (CF/VE) polymer matrix composites due to different electrochemical interactions when exposed to seawater or at high temperature had been experimentally investigated. Water uptake behavior of composite specimen was examined based on weight gain measurement. Three point bending test was performed to quantify the mechanical degradation of composite immersed in seawater with different environmental and electrochemical interactions. Finally, Electrochemical Impedance Spectroscopy (EIS) was used to better understanding of the degradation process in CF/VE composite produced by interactions between electrochemical and different environmental conditions. A detailed equivalent circuit analysis by using EIS spectra is also presented in an attempt to elucidate the degradation phenomenon in composites.

In this research, the degradation of carbon fiber/vinylester composites in marine environments was experimentally investigated. Additionally, two types of carbon fiber surface treatments, namely Polyhedral Oligomeric Silsesquioxane (POSS) and the industrial surface treatment F0E, were evaluated to determine their effectiveness in creating a fiber/matrix (F/M) interface for use in the marine environment. Electrochemical Impedance Spectroscopy (EIS) was explored as a new application of an existing technique for use in measuring the amount of water at the F/M interface in carbon fiber/vinylester composites. EIS spectra were used to determine equivalent electric circuit models that allow for the prediction of water at the interface. The location of water within the composite was determined through Positron Annihilation Lifetime Spectroscopy (PALS). Interlaminar shear strength and transverse tensile tests were carried out for dry conditions and after hygrothermal exposure of the composites to study the influence of the integrity of the F/M interface on the macroscopic response of the composite.

The increasing acceptance and incorporation of fiber-reinforced polymer matrix composites (PMCs) as engineering construction materials have led many to look to the infrastructure as an application for these versatile materials. One such system is pultruded graphite fiber-reinforced epoxy (graphite/epoxy). Some PMC systems degrade when subjected to environmental conditions (e.g., moisture, stress, UV light, electrochemical polarization). These variables are typically studied either singularly or in series, but in real applications (e.g., aerospace, marine, infrastructure), these materials are subjected to many of these conditions simultaneously. To simulate field conditions, this study investigated the combined effects of an aqueous environment, electrochemical polarization, and applied bending stress on the durability of a pultruded graphite/epoxy composite. The findings indicate that graphite/epoxy composites cannot be assumed to be insensitive to degradation by environmental variables. Further, electrochemical polarization, as might occur with contact with a metal such as a fastener, can accelerate degradation. This damage requires the presence of moisture. Chloride and sulfate concentrations in rain are sufficient to establish an electrolyte within creviced regions, but deicing salts would overtake these as a contributor to conductivity. Further findings may be summarized as follows: 1.) Application of polarization in an aerated 0.6M NaCl environment led to breakdown of the fiber/matrix interface. The high pH environment created during the oxygen reduction reaction was necessary but not sufficient to create this breakdown, as the unpolarized specimen exposed to a pH 13 environment did not degrade. Cathodic polarization as would occur by coupling to steel or aluminum is required. 2.)Application of cathodic polarization did not significantly alter strength. Average measurements of shear strength, however, did decrease with the application of cathodic polarization for 70 and 90 days.

Carbon Fiber-Reinforced Polymer (CFRP) composites with epoxy matrices offer many advantages over conventional materials in terms of high strength-to-weight and high stiffness-to-weight ratios, design flexibility, corrosion resistance, and electromagnetic shielding for naval vessels in marine environments. However, the risk of fire and related structural degradation represent a challenge to the structural assessment of high performance composite structures. The accurate assessment of the deterioration and degradation of a composite structure subjected to elevated temperatures is vital in the planning for maintenance of mission critical components. In this research, carbon/epoxy composite materials have been thermally aged at nine (9) different temperatures for up to 72 hours of ageing time. In order to determine the residual mechanical properties of the specimens exposed to elevated temperatures, tensile, flexure, off-axis shear, and short beam shear tests were conducted in accordance with ASTM test procedures. In addition, the viscoelastic behavior and dynamic properties of these composites at varying ageing times and temperatures were found using Dynamic Mechanical Thermal Analysis (DMTA) and Differential Scanning Calorimetry (DSC). ThermoGravimetric Analysis (TGA) was performed to analyze the characteristics of thermal decomposition and Scanning Electron Microscopy (SEM) images were taken to investigate failure mechanisms such as interfacial debonding, delamination, and fiber fracture. Since polymer composite used in marine environments can easily be exposed to moisture related to high relative humidity and immersion, degradation mechanisms related to moisture were investigated on specimens immersed in seawater and deionized water for 72 weeks after exposure to selected regimes of elevated temperature using gravimetric analysis, SEM and short beam shear test. Finally, well-established prediction models such as Arrhenius rate model, Time-Temperature Superposition model and Weibull statistical strength model were used with experimental data to estimate characteristic associated with long-term service life.

The galvanic interaction between metals and carbon fiber/polymer matrix composite degrades not only the metals but the composite itself. The objective of this study was to investigate if the fiber type influenced either the mechanism or form of damage. Two different composites were examined. Both have same epoxy matrix, 3501-6 epoxy, but contain different carbon fibers, either AS4 or IM6. The surfaces of the composite materials were exposed to 0.5 N NaCl solution to simulate sea water at open circuit condition or cathodic potentials to simulate galvanic coupling of metals. Electrochemical impedance spectroscopy (EIS) was employed to monitor changes in the behavior of the composites. Modeling of experimental data indicated that the parameter, Rp, representing the polymer resistance decreased with increasing time of exposure for both open circuit conditions and applied cathodic potentials. The value of Rp also decreased with increasingly cathodic applied potentials. This suggested that a damage process for the polymer involving increased access of solution to the carbon fibers. SEM examination showed that cracks and polymer separations on the exposed but not on the unexposed surfaces. The fiber type did not appear to influence the damage mechanism in this study.

Marine Composites: Design and Performance presents up-to-date information and recent research findings on the application and use of advanced fibre-reinforced composites in the marine environment. Following the success of their previously published title: Marine Applications of Advanced Fibre-reinforced Composites which was published in 2015; this exemplary new book provides comprehensive information on materials selection, characterization, and performance. There are also dedicated sections on sandwich structures, manufacture, advanced concepts, naval architecture and design considerations, and various applications. The book will be an essential reference resource for designers, materials engineers, manufactures, marine scientists, mechanical engineers, civil engineers, coastal engineers, boat manufacturers, offshore platform and marine renewable design engineers. - Presents a unique, high-level reference on composite materials and their application and use in marine structures - Provides comprehensive coverage on all aspects of marine composites, including the latest advances in damage modelling and assessment of performance - Contains contributions from leading experts in the field, from both industry and academia - Covers a broad range of naval, offshore and marine structures

Emphasizing fiber-matrix adhesion and its characterization in composite materials, reports results from applying the most commonly used test methods, such as fragmentation, pull-out, and indentation, to high-performance composites and their constituents. The 13 papers were presented at a symposium i