Ocean structures and their materials: from wood and iron, to composites and smart materials
22 July 2021Article by Miguel Onofre Gomes, product development engineer in the field of sea technologies at INEGI.
The oceanic environment has always posed significant challenges to the performance of the structures and equipment that operate in it. Whether due to the unpredictability and sometimes extreme nature of meteorological and oceanographic conditions, or the effect of this environment on structures - through corrosion and encrustation of micro-organisms, algae or animals - the selection of suitable materials, with the right mechanical properties, has a leading role in ocean engineering.
The study of materials in this area of engineering has, therefore, been monitoring and «borrowing» the knowledge and developments of other industries and technical areas. Whether for the manufacture of ships, equipment or offshore structures, the selection of materials has always been strongly linked both to the available manufacturing techniques and the availability of resources.
A science with centuries of history
The oldest vessel we know of, discovered near the great pyramid of Giza and dating from around 2500 BC, was built with cedar wood1. Although, during the Bronze Age, certain smaller elements made of metallic alloy and, later, structural reinforcements made of iron appear, wood remained the material of choice in shipbuilding until the 19th century. At this time, iron appeared, available for the first time in the form of large slabs, thus replacing wood, allowing for the manufacture of larger ships.
In the 1940s, materials such as steel (due to their high mechanical strength) and aluminum (due to their reduced weight) gained popularity. Later, due to the growth of offshore oil exploration in the 1960s to 1980s, high performance metals began to be used for specific applications, such as titanium and nickel alloys.
We jump to the present day and observe that the latest developments in materials engineering influence ocean engineering in equal measure. We are talking about materials such as composite laminates, new metal alloys and high performance polymers. An example of this is the application of composites, such as carbon fiber, in equipment for high competition water sports, motivated by the search to reduce their weight.
It is important to look at the Global Marine Technology Trends 20302 report, which points to the areas of maritime transport, naval defense and ocean space, 8 technological areas in which scientific development will have the greatest impact until the end of this decade. The development of advanced materials is indicated as having a transversal impact on the three areas.
According to this study, the materials of the future will be stronger, longer lasting and lighter, will allow the sensing of the surrounding environment and will have self-cleaning and self-repair capabilities. They will also be intelligent, and their structural integrity will be remotely assessed via sensors.
Bio-inspired coatings will result in surfaces with better hydrodynamic characteristics, leading to reduced fuel consumption by ships and a consequent reduction in greenhouse gas emissions. Changes in the structure of metals to the nanometer scale will lead to improved corrosion resistance.
There are new materials to be born with input from INEGI
The vision presented in this publication has not yet become a reality, but the path is set and it is up to the R&D&Innovation sector to work in the application of new materials in an oceanic environment.
This vocation for the sea also marks the performance of INEGI, whose multidisciplinary approach has been deepened, responding to the demands of an industry thirsty for change and technological updating.
An example of this is the recent work developed with polyoxymethylene (POM), a thermoplastic with high performance, high rigidity and low density, reduced friction and very good corrosion resistance. The mechanical properties of this material were experimentally characterized in INEGI's laboratories, through tensile and impact tests. The resulting knowledge informed the development of mathematical models of mechanical behavior, later used in the design of underwater structures.
Thanks to INEGI's contribution, this material gave body to a marine observatory for monitoring invasive algae, capable of operating to depths of 200m3.4, and a docking station for autonomous underwater vehicles5 , among others.
In 2021, we also embraced the challenge of participating in the European project MAREWIND, focused on the development of new solutions in the area of materials, aiming to reduce the cost and to extend the service life of equipment used in the offshore wind energy sector.
We will help create new concrete formulations specific to ocean environments, composite materials, coatings to protect materials against corrosion and encrustation of biological material, among other aspects that are expected to contribute to the competitiveness of this form of renewable energy. These aspects will also be tested in a real environment, with the installation of structures duly sensed and monitored, in order to record and study the behavior of materials in this environment.
What materials will the ocean structures of the future be made of? INEGI is working to offer possible solutions. Taking advantage of a broad spectrum of engineering knowledge, we help to develop new materials with exceptional properties to modernize marine activities.
References
[1] United States Naval Academy, "EN380 Naval Materials Science and Engineering Course Notes”.
[2] Lloyd’s Register, QinetiQ, University of Southampton, "Global Marine Technology Trends 2030”, 2015, ISBN: 978-0-9933720-1-8.
[3] F. Assis Gonçalves, M. Onofre Gomes, N. Mathias, T. Morais, and T. Ferradosa, "Numerical modelling of full-scale subsea lander AMALIA with in-situ conditions,” Proceedings of the Institution of Civil Engineers - Maritime Engineering, pp. 1–32, Mar. 2020.
[5] INTENDU
[6] MAREWIND