Abstract
Fiber reinforced polymer (FRP) composites coupons were exposed to real sea environment to assess the influence on the mechanical behavior of composite materials used in the construction of marine structures. Real-life sea environment conditions were opted for instead of the more common simulated and laboratory versions of seawater in the attempt to obtain more realistic structural modeling environmental input design parameters for marine structures. Exposure was performed over prolonged time span instead of the usual accelerated tests. Epoxy and polyester resins, reinforced with glass fibers in three fiber layout configurations, were used to manufacture standardized tensile testing coupons. Mass changes due to seawater absorption, microorganism growth, changes in tensile strength (standard tensile tests), and surface morphology of the coupons were evaluated after 6- and 12-month long periods of submersion in the sea in the Rijeka bay, Croatia. All specimens showed mass increase due to water absorption and growth of attached algae and sea microorganisms. Various levels of reduction in tensile strength, depending on the fiber layout configurations, were observed. Significant changes in the matrix material structure were noticed, effectively producing “voids”. Based on these results, sustainability of FRP composites in marine environment is addressed and discussed.
Highlights
Fiber reinforced polymer (FRP) composites were used in the construction of marine vessels and structures since the middle of the 20th century, whether it be as an exclusive option for construction [1] or as a combination with traditional materials, such as steel [2]
Engineering stress-strain diagrams were from performed uniaxial tensile strength on dry coupons and wet coupons thatobtained were submerged in the sea for 6 and strengthFigures on dry7–12
Considerable effects of the real sea environment on composite materials were noticed in the form of reduced mechanical strength for the tested coupons submerged in the sea
Summary
The design of these structures in aspects of strength, durability, and environmental influence on the mechanical properties was based mainly on experience for the best part of the said period. In the last couple of decades, significant effort was made to combine the experimental and scientific knowledge obtained so far in these field of research to enable prediction models that can be safely used to achieve sustainable and safe design of marine structures [4,5,6,7]. Mechanical properties of composite materials can be customized to specific applications demands by defining layup sequences, number of plies, and fiber orientation in the load direction [8,9,10], which makes them appealing for design of marine structures with complex shapes. Adequate knowledge of limit state assessment, durability and life span, failure modes, fracture toughness, fire resistance, and environment influence parameters are crucial for an efficient and sustainable design process for structures in this demanding industry sector [11]
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