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Durability of the composite materials in marine environments has been investigated experimentally and with analytical and numerical methods. The main focus of this study is on the integrity of the fiber/matrix interface under seawater exposure. A single-fiber compression test specimen called the Outwater-Murphy (OM) test has been analyzed using mechanics of materials principles and linear elastic fracture mechanics. Sizing of the OM specimen was conducted so that debonding of the fiber from the interface should be achieved prior to yielding of the matrix and global instability failure. Stress analysis of the OM specimen has been conducted from theory of elasticity and finite element analysis. A superelement technique was developed for detailed analysis of the stress state at the fiber/matrix interface. The interface stress state at the debond site in the OM specimen, i.e. at the hole edge, was identified as biaxial tension at the fiber/matrix interface. Characterization of cure and post-cure of 8084 and 510A vinlyester resins has been performed using cure shrinkage tests based on dynamic mechanical analysis and coated beam experiments. In addition, moisture absorption, swelling and the influence of moisture on the mechanical properties of the resins were determined. Testing of OM specimens consisting of a single carbon or glass fiber embedded in vinylester resin at dry conditions and after seawater exposure revealed that the debond toughness was substantially reduced after exposure of the OM specimen to seawater. C(F) did not debond. Macroscopic carbon/vinylester woven composites where the fibers were sized with F sizing were tested in shear at dry conditions and after four weeks of seawater exposure. The shear strength was very little affected after the short immersion time.
Composites are widely used in marine applications. There is considerable experience of glass reinforced resins in boats and ships but these are usually not highly loaded. However, for new areas such as offshore and ocean energy there is a need for highly loaded structures to survive harsh conditions for 20 years or more. High performance composites are therefore being proposed. This book provides an overview of the state of the art in predicting the long term durability of composite marine structures. The following points are covered: • Modelling water diffusion • Damage induced by water • Accelerated testing • Including durability in design • In-service experience. This is essential reading for all those involved with composites in the marine industry, from initial design and calculation through to manufacture and service exploitation. It also provides information unavailable elsewhere on the mechanisms involved in degradation and how to take account of them. Ensuring long term durability is not only necessary for safety reasons, but will also determine the economic viability of future marine structures.
This book presents selected papers from the 2nd Workshop on “Durability of Composites in a Marine Environment”, which was held in Brest, France in August 2016. Providing an overview of the state of the art in predicting the long-term durability of composite marine structures, it addresses modelling water diffusion; damage induced by water accelerated testing, including durability in design; in-service experiences; ocean energy; and offshore applications. Ensuring long-term durability is not only necessary for safety reasons, but also determines the economic viability of future marine structures, and as such, the book is essential reading for all those involved with composites in the marine industry, from initial design and calculation through to manufacture and service exploitation. It also provides information unavailable elsewhere on the mechanisms involved in degradation and how to take account of them.
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.
Damping in Fiber Reinforced Composite Materials starts with an introduction to the basic concepts of damping in composite materials. Methods of modeling damping are then covered, along with recent developments in measuring techniques, both local, like polar scanning and global techniques like the Resonalyser method (based on measuring modal damping ratios of composite material plates). The effect of other factors, such as stress, strain-level, stiffness and frequency that need to be considered when determining damping behavior in composite materials are also discussed in detail. Other chapters present a parametric study of a two-phase composite material using different micromechanical models such as Unified micromechanics, and Hashin and Eshelby’s to predict elastic moduli and loss factors. A bridging model that incorporates the effect of fiber packaging factors is then compared to FEM results. Final sections cover the effect of the interphase on the mechanical properties of the composite, present a nonlinear model for the prediction of damping in viscoelastic materials, and provide practical examples of damping and principles of vibration control. Introduces the basics of damping and dynamic analysis in composite materials Explains damping mechanisms in fiber reinforced composites and modeling principles Covers recent developments in measuring techniques for the identification of damping in composite materials Explains the use of a dynamic mechanical analyzer for predicting damping in composite materials Contains micromechanical studies, modeling of two and three-phase composites, and modeling of non-linear damping Includes experimental results that validate micromechanical models
Durability and Life Prediction in Biocomposites, Fibre-Reinforced Composites and Hybrid Composites focuses on the advanced characterization techniques used for the analysis of composite materials developed from natural fiber/biomass, synthetic fibers and a combination of these materials used as fillers and reinforcements to enhance materials performance and utilization in automotive, aerospace, construction and building components. The book presents key aspects of fracture and failure in natural/synthetic, fiber reinforced, polymer based composite materials, ranging from crack propagation, to crack growth, and from notch-size effect, to damage-tolerant design. Written by leading experts in the field, and covering composite materials developed from different natural fibers and their hybridization with synthetic fibers, the book's chapters provide cutting-edge, up-to-date research on the characterization, analysis and modelling of composite materials. Contains contributions from leading experts in the field Discusses recent progress on failure analysis, SHM, durability, life prediction and the modelling of damage in natural fiber-based composite materials Covers experimental, analytical and numerical analysis Provides detailed and comprehensive information on mechanical properties, testing methods and modelling techniques
The usage of composites is a broad and growing area of scientific research, especially in developed and developing countries. These materials are used in a broad range of applications in both structural and civil engineering sectors. In many of these applications FRPs are exposed to one or more environmental influences, so they need to be designed to meet durability requirements to withstand even the harshest of environments. Aging and Durability of FRP Composites and Nanocomposites focuses on the latest developments in durability and long-term ageing studies of composite materials especially for those used in civil and structural engineering applications. The book will be a valuable reference resource for materials scientists and engineers who want to learn more about the long-term service life and durability behaviour of composites under different environmental conditions. Discusses composites and polymer nanocomposites Reviews different types of aging processes and degradation mechanisms in composites Covers different types of accelerated aging tests Presents theory, modeling, and simulation studies of aged composites and nanocomposites Looks at recent trends and future possibilities
Military use of advanced polymer matrix composites (PMC)â€"consisting of a resin matrix reinforced by high-performance carbon or organic fibersâ€"while extensive, accounts for less that 10 percent of the domestic market. Nevertheless, advanced composites are expected to play an even greater role in future military systems, and DOD will continue to require access to reliable sources of affordable, high-performance fibers including commercial materials and manufacturing processes. As a result of these forecasts, DOD requested the NRC to assess the challenges and opportunities associated with advanced PMCs with emphasis on high-performance fibers. This report provides an assessment of fiber technology and industries, a discussion of R&D opportunities for DOD, and recommendations about accelerating technology transition, reducing costs, and improving understanding of design methodology and promising technologies.