In the context of modern requirements to structural materials, laminated composites attract much attention from professionals working in almost all industries. Laminates have a sandwich structure with separate layers bound in a monolith by a matrix material.
Laminated composites have huge potential due to almost unlimited reinforcing and matrix materials, and offer the possibility of developing high-strength, corrosion-resistant and lightweight materials, including thin-walled hollow products.
Matrix materials are comprised of metals and alloys, carbon and ceramics, organic and inorganic polymers. The choice depends on the physicochemical and operational properties required for the final product. Combining the most relevant properties of each component, a developer can obtain innovative structural composites with properties surpassing traditional materials.
Well-matched matrix and reinforcing material enable the developers to compensate for the negative characteristics of some components, attaining almost perfect material properties relevant to the application field, given the range and types of expected loads and operating conditions.
Matrix is assigned an important role: to ensure density of the product, to secure its shape and reinforcing materials allocation, to distribute stresses in the composite volume, providing a uniform load on the filler and the load redistribution upon the destruction of some part of the filler.
Requirements for matrix materials can be divided into
- operational, which are related to the mechanical and physicochemical properties of the matrix material, ensuring the workability of the composition under various operational factors;
- technological, which ensure efficient joint operation of fibers under various types of loads.
Equally important is the complex of operational and technological requirements, which reinforcing material has to satisfy:
- operational requirements, such as strength, rigidity, density, stability of properties in the required temperature range, chemical resistance;
- technological requirements that determine the feasibility of organising a highly efficient manufacturing process of fiber reinforced products.
Laminated composites are usually reinforced with fiber, bands, fabrics, tows, woven and non-woven textiles, it is also possible to combine different types of materials in one composition. Individual plies of a matrix component can be disperse reinforced.
Properties and cost place basalt fiber in the intermediate position between carbon and fiberglass. This is a reason why designers increasingly select it as a filler in hybrid laminated composites, e.g. combining it with carbon and glass reinforcement.
Specialists from the University of Trento (Department of Industrial Engineering, Italy) combined fabrics from basalt and E-glass fibers with fabrics made from carbon fiber in order to prepare epoxy-based interlaminar hybrid composites and to investigate the hybridization effect on the flexural and impact properties of the resulting laminates.
The tests on flexural modulus detected an important synergistic effect, while Charpy impact tests evidenced a strength increase as basalt and glass fibers content increased. Interestingly, hybridization with basalt fibers promoted an increase of the adsorbed impact energy due to an enhancement of the fracture propagation component. The observed improvements are related to the increased ability of basalt / carbon laminates to prevent the spread of damage and delamination without catastrophic failure.
Alongside with experimental studies and scientific research, laminated composites find way to various sectors of industry.
Ecole de Technologie Superieure (School of Higher Technology in Montreal, attached to Quebec University) uses the technology of hybrid laminates reinforced with basalt fiber to create a series of Omer submarines that several times set world speed records at the European and American international competitions among submarines driven by human power.
The International Submarine Race (ISR) takes place under the auspices of the Foundation for Underwater Research and Education (FURE). It is hosted by the Naval Surface Warfare Center. The European International Submarine Race (EISR) is organized by the IMarEST, the international institute and scientific foundation that unites marine engineers, scientists and technologists. The competition is sponsored mainly by companies from the defense sector.
The weight of organizers and backers prove that such kind of competitions is a platform for experimental research of the latest technologies, materials, solutions and application methods.
Omer designers decided against glass fiber combined with balsa and started to leverage basalt fiber strengthened with an outer layer of carbon fiber.
The team explained the decision to use basalt fabrics as a main structural material for the submarine as follows:
«Fiber choice was one of the first steps in designing the hull. Indeed, fiber properties have great importance. We have considered several options, such as carbon fiber, fiber glass, INEGRA (polyester carbon) and basalt fiber. Each fiber type has its advantages and disadvantages.
Carbon has a benefit of being extremely strong and relatively lightweight, but it is an expensive material. Glass fiber is not so strong, but much cheaper. INEGRA has a good impact resistance and some properties the carbon fiber offers. Finally, basalt falls in between glass and carbon fiber according to the strength, but its cost is comparable with glass fiber. For economic reasons, basalt fiber was the chosen solution. Actually, it has a good price/strength ratio.»
Economic aspects play an important role when using basalt products for hybrid laminated composites. Having been niche materials composites are gradually coming into a sphere of industrial application, where costly materials will be replaced with cheaper ones but capable of ensuring sufficiently high performance for the products. Leading technology developers and manufacturers of structural composite machinery definitely point to this aspect.
For instance, British company Creative Composites presented a powerful compression unit for compression moulding of polymer composites in 2016. The press generates 1,500T of moulding pressure and is capable of processing tools up to 3 metres by 2 metres in size. The new press is capable of working with different types of fibers including basalt fiber and will be used to meet growing demand for high quality composite components in the automotive, aerospace and construction sectors that require extremely durable components.
A year later Henkel opened Composite Test Center in Asia to meet demand of automotive OEMs that express a lively interest in applying composite materials in their products. Henkel’s customers can work with experts to develop and test composite parts, as well as optimize conditions for series production process. They carry out trials on Henkel’s own High Pressure Resin Transfer Molding (HP-RTM) equipment, which models close to real conditions.
Not long ago a manager from an affiliate of well-known Firestone Fibers & Textiles commented that the company was experimenting with basalt materials. Firestone Fibers & Textiles is engaged in R&D and manufacturing of unidirectional and multiaxial fabrics used for tires and automotive belts, conveyor belts, roofing materials and inflatable boats, tents, coated fabrics and rubber products such as hoses, air ducts, etc.
The issues of sustainability and recyclability of structural materials have recently come into sharp focus on a global scale. Reducing weight of the vehicles and the ‘carbon footprint’ in the course of production and operation, as well as energy efficiency of structures and all modes of transport dictate the conditions when it is necessary to apply composite materials. Manufacturers are increasingly experimenting with natural and basalt fibers for various purposes, because they best meet ecology requirements.
Italy-based GS4C is one of the companies specializing in researching, developing, prototyping and promoting sustainable and recyclable solutions to the global market, also creating zero landfill Cradle to Cradle manufacturing process.
Having decided that basalt fiber is the best compromise between efficiency and sustainability, the company patented the technology to obtain out of autoclave Fiber Metal Laminate, a composite material made of thin layers of aluminum and fiber consolidated by a vacuum assisted infusion process.
Austria-based Niche successfully develops lines of fully recyclable but quality snowboards highly assessed by the specialists. Sustainable sport equipment managed to obtain two Good Wood Awards in 2017/18 season.