Application status and development trend of marine composite materials

Compared with traditional metal structural materials, composite materials have a higher strength/mass ratio. The use of composite materials to build hulls and structures is lighter and has better performance in fuel consumption and speed improvement.


At the same time, composite materials also have the advantages of corrosion resistance, non-magnetic, and good plasticity. Therefore, since the advent of composite materials, they have been playing an important role in the shipbuilding industry. The application research on ships has always been the focus of major shipbuilding countries. focus.


The article gives a brief introduction to marine composite materials, and describes the development history and application status of marine composite materials at home and abroad. On this basis, the development trend of marine composite materials is analyzed and prospected.


1 Definition of composite materials


A composite material is a multiphase solid material composed of two or more substances with different physical and chemical properties. Although each component material of the composite material still maintains its relative independence, the performance of the composite material is not a simple addition of the performance of the component materials, but shows a performance far superior to both.


Usually one phase in the composite material is the continuous phase, called the matrix, used to bond, fix, and maintain the reinforcement material into a certain shape; the other phase is the dispersed phase, called the reinforcement phase or reinforcement, the reinforcement material is in the composite material It does not constitute a continuous phase, it provides strength and rigidity with matrix support. The dispersed phase is distributed in the entire continuous phase in an independent form, which can be a reinforcing fiber or a granular dispersed material.


There are many classification methods for composite materials, and the most basic ones can be divided according to the type of matrix material: polymer matrix composite materials, whose matrix is organic polymer macromolecule; metal matrix composite materials, whose matrix is metal, such as aluminum matrix composite material, iron Matrix composite materials, etc.; inorganic non-metal matrix composite materials, the matrix of which is ceramic materials (including glass and cement, etc.).


 2 Classification of marine composite materials


At present, marine composite materials, especially composite materials used in hull structures, are mainly based on polymer-based composite materials. According to the structure, they can be divided into two major types of laminates (fiber reinforced composite materials) and sandwich structure composite materials, including three Important composites in all aspects: reinforcement materials, resins (ie matrix) and core materials.


Marine composite materials can be divided into: main load-bearing structure, secondary load-bearing structure, non-bearing structure, etc. according to different load-bearing parts. According to the function, it can be divided into five series of materials: structure, damping, acoustics (including sound absorption, sound insulation, sound transmission), stealth (including wave absorption, wave transmission, reflection, frequency selection), protection, etc. The classification and classification of marine composite materials The application parts are shown in Figure 2.


The superiority of the performance of marine composite materials is mainly reflected in: light weight and high strength, which can effectively improve the reserve buoyancy of the hull; structural and functional integration, performance can be designed under the condition of satisfying the structural load, usually with acoustics, radar, vibration reduction, protection, Low magnetic properties and other properties, the general material forming process is also a structural forming process; corrosion resistance, can meet the harsh marine environment requirements of high salt, high humidity, ultraviolet, etc.;


Anti-aging, can meet the long life requirements of ships. The above characteristics are different from other ship structural materials, and are also its advantages. The main types and typical applications of marine composite materials and structures are reflected. Starting from small speed boats, the application of composite materials on ships has gone through three stages.


The first stage is mainly used on small ships such as minesweeper boats. It has low performance requirements and can be integrally formed. In the second stage, it is partially used on large and medium-sized ships, but the concept of use is still limited to the traditional hull design. Composite materials only play an auxiliary role on the ship such as reducing the quality and improving the corrosion resistance of components. In the third stage, at the beginning of the design, the ship fully considered the various complex situations in use, using composite materials as the main hull material to achieve the effects that other materials could not achieve or difficult to achieve. At present, marine composite materials have broken through the second stage and developed to the third stage.


   3 Development status and application status of marine composite materials at home and abroad


   3.1 Development and application status abroad


Early composite materials were used in small patrol boats and landing ships. The relatively poor manufacturing quality and hull rigidity limit the length of the ship to 15 m and the displacement to 20 t.


In recent years, with the reduction of composite material design and preparation costs, and the improvement of mechanical properties, composite materials have begun to be applied to large ships such as mine-hunting boats and light frigates. With the development of technology, the length of ships has been increasing steadily. There are now 80-90 m long all-composite naval ships.


The United States is the country with the most advanced development of composite materials science and technology, the most widely used composite materials, and the largest dosage. In terms of the application of marine composite materials, its scale and technology are in the forefront of the world. In 1946, the US Navy built a transportation boat using polyester fiberglass, which was the world's first composite ship, and subsequently manufactured fiberglass landing craft and work boats.


In order to accelerate the development of FRP ships, the US Navy stipulated that ships under 16 m must be made of composite materials in the mid-1950s. Around 1954, the hand lay-up molding process in the United States became more and more mature. In 1956, two small minesweeper boats with different structures were built, and the application research of FRP in minesweeper boats began.


In the early 1960s, the U.S. Navy manufactured the first all-glass fiber reinforced plastic patrol boat. The late 1980s and early 1990s built a composite material hunting/sweeping boat. The hulls were all made of high-grade m-phenylester resin and were semi-automatically dipped. Glue operation manufacturing, at the same time, a patrol boat with a single shell structure of polyester resin reinforced by Kevlar was manufactured. Subsequently, the US Navy introduced composite materials into the manufacture of deep submersible vehicles.


The submersible built with graphite fiber reinforced epoxy resin in 1966 has a dive depth of 6096m. After entering the 21st century, the United States has further strengthened the application of composite materials in shipbuilding. It uses a new high-strength carbon fiber/vinyl resin sandwich structure to replace low-strength fibers such as traditional glass fiber. The new ship built has high stability and fast speed. And has stealth, anti-submarine, anti-mine capabilities. The European composite shipping industry is also very developed.


In the mid-1960s, the United Kingdom used FRP to manufacture 450-ton minesweepers and 625-ton mine-hunting boats. In 1973, it used composite materials to build all-fiber reinforced plastic anti-water mineboats. Its successful application promoted the rapid development of composite materials. In the early 1980s, more than 200 all-composite anti-mine mine ships were manufactured.


In the 1990s, the United Kingdom successfully used carbon-glass hybrid fibers to build motor boats and patrol boats. With the development of technology, in recent years, it has also successfully used recycled plastic bottle reprocessing materials to build ships, which not only reduces costs, but also meets The development direction of material biodegradation and recycling.


Sweden built the first sandwich-structured FRP minesweeper in 1974. In the 1990s, it successfully developed the world’s first composite stealth test boat, and gradually developed a high-performance carbon fiber and sandwich structure. Construction method, developed and built a series of light destroyers integrating advanced composite technology and stealth technology, which has been successfully launched into service.


In the mid-1980s, Italy began to build several FRP minesweeping boats one after another. Japan has been building FRP boats since the 1950s, and has achieved good results in the construction of high-performance boats, rowing boats and luxury yachts. In the 21st century, Japan began to research and manufacture high-performance composite military ships. At present, the first FRP minesweeping boat has been successfully built and put into use.


Composite materials used by navies in various countries also include ship superstructures, propellers, and masts. The French Navy began to use composite materials in the ship's superstructure in 1992, which can effectively reduce the quality of the ship. The former Soviet Union first used composite propellers for real ships [18-19].


Sweden began to develop composite propulsion shafts in 1989. Thousands of different materials and surface treatment methods were tested and evaluated to obtain the best performance of the shaft. The produced propulsion shaft is light in weight, good in elasticity, strong in adaptability, and not Conductive and corrosion resistant. The United States began using composite materials in 1995 to study advanced fully enclosed masts, and successfully equipped it with destroyers and aircraft carriers.


In addition, because composite materials can reduce the radar signal characteristics and infrared (thermal) signal characteristics of ships, composite materials are also widely used in chimneys, bulkheads, decks, rudders and other sub-bearing structures, contributing to stealth and structural weight reduction. Very significant.


3.2 Domestic development and application status


The research and application of composite materials in my country began in 1958, and the first FRP work boat was born in Shanghai. In the mid-1970s, a mine-sweeping test boat with a total length of approximately 39 m was developed. After that, the research and development of GRP/CM anti-mine minecraft was interrupted for more than a decade.


Since the 1990s, with the development of technology and the introduction of technology, China has produced a large number of yachts, sailing boats, rescue boats, and high-speed patrol boats, law enforcement boats, and anti-smuggling boats, such as public security, armed police, marine surveillance, and customs, using composite materials. Waiting for paramilitary boats, but so far has not designed and built a high-tech naval anti-mine mine ship.


In terms of composite ship components, my country successfully developed composite material sonar shrouds in the late 1960s and applied them to submarines, which have developed into more mature applications so far. In the late 1980s, composite material radomes and mine shells were developed and put into use. In the 1990s, composite material masts and superstructures were successfully developed for large surface ships.


Compared with foreign countries, the application scope and scale of my country's marine composite materials are still relatively small. In terms of raw materials, at present, China has been able to produce most varieties of reinforced materials for FRP on the international market, but compared with developed countries in the world, there is still a large gap in product technology level, variety, specifications, quality, etc. Carbon fiber, High-performance fibers such as aramid fibers still rely on imports, and resin production capacity is also seriously lagging behind.


In terms of molding processing, the RTM process has received widespread attention and rapid development due to its advantages of good product quality and high production efficiency. It has developed quite maturely in industrialized countries and is constantly improving, while China has only started since the 1980s The introduction of RTM technology and equipment, less investment in production, and low equipment utilization, the current RTM technology is still in the development stage. Compared with foreign countries, my country's current application technology and research and development in the field of marine composite materials are still relatively backward, and there is still much room for development.


  4 Problems


Although composite materials have a long history of application in foreign naval powers, although China's speedboats, diversion covers and other aspects have also been applied, but progress has been slow, because the characteristics of composite materials are different from traditional metal materials. Composite materials It has strong designability, and its material properties are closely related to the manufacturing process, but currently there is a lack of relevant design specifications, empirical data, and reliability evaluation technology and indicator systems. At present, the problems of composite materials in ship application mainly include the following aspects.


1) Design and manufacture of high-performance and low-cost marine composite materials


For many years, in most shipbuilding applications, composite materials have not been competitive in cost compared to traditional materials (except wood). So far, most composite material structures are made of resin-impregnated reinforced materials. This process is long, labor-intensive, expensive, and difficult to control product quality. The production of high-quality composite materials requires ship manufacturers to introduce new manufacturing methods, and ship manufacturers are lacking models and large and stable database information to predict the manufacturing cost of composite material structures.


2) Reliability evaluation technology and index system of marine composite materials


Ship structures are prone to failure when subjected to shocks, vibrations, collisions and fires. However, there is currently no analytical tool that can determine whether they are failing. In addition, due to the anisotropy of the composite material, the scaling rules are particularly complex, so the structural design is much more complicated than metal.


3) Accumulation of basic data on the performance of marine composite materials


Limited data accumulation hinders the application of composite materials on ships. The composite material structure needs to pass a series of strict regulations, including physical and mechanical properties, environmental aging performance, resistance to airflow impact, resistance to underwater vibration damage, fire performance (flammability, open flame, smoke, toxicity, structural integrity), debris/ Ballistic protection and radar/sonar performance.


The data required to evaluate the reliability of the structure and function of composite materials is extremely limited, and testing to determine the performance of composite materials under shock, vibration, ballistic and open flame conditions is a long and expensive task. Assessing the safety and reliability of composite materials and meeting design requirements is a major issue facing marine applications on composite materials.


5 Development trend of marine composite materials


Composite materials have great advantages in ship applications. Speeding up the design and development of composite materials is the main problem that hinders their application in ships. The future development direction of marine composite materials is first of all to improve the design process.


The development trend of composite materials is to design and manufacture high-performance, low-cost composite materials, promote the development of composite materials from non-load-bearing structures to primary/secondary load-bearing structures, expand from local use to large-scale applications, and increase the research and application of composite materials. It has the characteristics of low cost, high performance, multi-function, optimized connection, long life, safety and reliability.


The development of a composite material with a single load-bearing function to a multifunctional composite material with bulletproof, sound insulation, sound absorption, damping, radar stealth and other characteristics. At the same time, it is convenient to research and develop between the composite material structure and its steel structure. , Reliable connection technology, etc.


Another development direction of marine composite materials is to conduct a comprehensive study on the design, process and manufacturing of composite materials, formulate unified and standardized design standards, and carry out technical research on composite material performance evaluation.


Based on the current research of composite sample performance, focusing on the typical structural elements and local models of composite materials, the performance parameters such as aging performance, fatigue performance, flame retardant performance, anti-explosion performance, and impact resistance performance are tested to form coverage Composite material samples, typical structural units, and local model performance test methods promote the large-scale application of composite materials on ships.


At the same time, the development of marine composite material process evaluation technology, taking the typical parts of the marine composite material as the object, study the quality consistency of the process samples, and form a marine composite material process evaluation method.


According to the analysis and summary of different application environments of marine composite materials, several typical composite materials are taken as the research objects, relying on the environmental test platform, through a large number of long-term marine environmental performance tests of composite materials (such as: full seawater immersion, tidal range, atmospheric exposure Etc.) and laboratory simulation accelerated performance tests to obtain the performance evolution of composite materials in the marine environment, and establish a life prediction model to form a marine composite material marine resistance evaluation program, process and method for structural design of composite materials, long-term Provide technical support for reliable application, maintenance and replacement.