Fiber types
Fiber types for fiber-reinforced concrete exist in many different sizes, forms, colors, and flavors.
Here are some examples of fiber types:
Macro-Synthetic Fibers: Macro synthetic fibers, also known as ‘structural’ synthetic fibers, are made up of a mixture of polymers and were designed to replace steel fibers in certain applications.
Micro-Synthetic Fibers: Microfibers are utilized in concrete to prevent shrinkage fractures caused by plastic shrinkage. Plastic shrinkage fractures form whenever the concrete is still soft or movable. The loss of moisture at the concrete’s surface is the most common cause of these cracks.
Poly-Vinyl Alcohol (PVA) Fibers: Wet spinning produces high-strength polyvinyl alcohol fiber with a high modulus polyvinyl alcohol (PVA) as the primary raw material.
Steel Fibers: Steel fiber is a type of metal fiber that is used to strengthen structures.
Steel & Micro/Macro Blends: These mixes assist to reduce plastic shrinkage cracking while simultaneously giving concrete with increased toughness and post-crack load bearing capability that can only be reached with steel and macro-synthetic fibers.
Glass Fibers: Glass fibers allow the production of extremely thin parts with high tensile strength. When compared to traditional steel-reinforced concrete panels, glass-reinforced concrete (GRC) panels lower the weight and thickness of the concrete by up to ten times.
Specialty Fibers: Optical fibers with at least one specific feature that differentiates them from normal fibers are known as specialty optical fibers.
Cellulose fibers: are made from processed wood pulp or cotons, are used to regulate and mitigate plastic shrinkage cracking in the same way that micro-synthetic fibers are. Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified cellulose such as the cellulose acetates.
Commom types of Fiber-reinforced composites/FRC
Any construction material made up of two or more constituent elements with differing physical qualities is called a fiber-reinforced composite. Fiber-reinforced composites（or FRC） are designed to provide materials with high specific strength and modulus.
1.Fiber reinforced metal matrix composites (MMCs)
Metal matrix composites (MMCs) are a type of lightweight, high-specific strength material used in a number of industries, particularly automotive, aerospace, and thermal management.
Fiber-reinforced metal matrix composites provide a diverse set of material qualities that can be used to satisfy a variety of design and application needs. They mix a fiber’s strength and modulus with a matrix’s flexibility and oxidation resistance.
Dispersion strengthening and dislocation blocking are two ways that the particles improve the mechanical characteristics of a matrix.
Fiber reinforcement, on the other hand, joins with the matrix to produce a strong composite body. The fibers carry the majority of the applied stress and aren’t usually thought of as dislocation motion barriers.
When particles are used as reinforcements, they provide the material isotropic qualities, whereas whiskers and fibers give it some directionality. In the direction parallel to the axis of the fibers, the characteristics of a fiber composite are superior than those in the transverse direction.
Most common application areas of composite reinforced metal matrix materials:
1. Pushrods for racing engines
Pushrods for valves in engines are made of aluminum MMC reinforced with fibers. Al2O3 fibers are employed as reinforcing material, whereas aluminum alloys are used for the matrix. Engine valve pushrods manufactured of alumina MMC offer a 25% better flexion stiffness and a twice larger absorption capacity than similar components made of ordinary steel.
2. Carbide drills
The toughest and most brittle of the drill bit materials is carbide (Carb). It’s mostly utilized for production drilling, which necessitates the employment of a high-quality tool holder and equipment. It should not be used in drill presses or hand drills.
3. Tank armors
Gradient MMCs have a long history of application in military systems. Gradient MMCs, for example, can be employed as protective armor plates on tanks and armored vehicles due to their constant dispersion of ceramic reinforced particles.
4. Automotive industry – disc brakes, driveshaft, engines.
Carbon fiber reinforced polymer matrix composite is the primary material used in the creation of the body of certain extremely costly sports vehicles, such as Bugatti.
5. Aircraft components – structural component of the jet’s landing gear.
The landing gear, also known as the undercarriage, is a complicated system that includes structural elements, hydraulics, energy absorption components, brakes, wheels, and tires. High-strength steel and titanium alloy are the most often utilized materials for landing gear because they offer high static strength, excellent fracture toughness, and fatigue strength.
The major purposes of landing gear, which connects the aircraft’s basic structure to its undercarriage, are to allow the aircraft to taxi, land safely, and take off, as well as to sustain the aircraft for the rest of the ground operation.
6. Bicycle frames
Bicycles have long been a part of daily life. It is also an essential form of transportation. Bicycle frames are usually made by welding metal pipes composed of iron-based materials, aluminum, or titanium, but more recently, FRP pipes made from carbon fibers or aramid fibers are used to build a higher-quality or lighter-weight bicycle frame. To distribute the load, most bicycles nowadays are made of heat treated alloy steel, aluminum, or titanium alloy tube.
FRP pipes and metal joints or lugs are bonded together by an adhesive in the structure of a FRP pipe bicycle frame, but FRP frames with FRP lugs are preferred when attempting to lighten or obtain required frame characteristics, such as mechanical strength and rigidity, best suited to a particular use.
7. Space systems
FRCs are utilized in aerospace vehicles, launch vehicles/spacecraft for space projects, and in the sector of sports and games. Only FRCs can provide the necessary strength-to-weight ratio while still maintaining all of the standards.
The use of fiber-reinforced composites (FRC) in industrial and clinical applications is expanding in order to sustain growth in all areas of reducing technology. FRCs have received a number of attention in the chemicals industry and other industries.
Fiber-reinforced ceramic matrix composites (CMCs)
Ceramic matrix composites (CMCs) have become more important in industry as a result of their unique properties. Ceramic matrix composites (CMCs) are a form of composite material in which the reinforcement (refractory fibers) and matrix material are both made of ceramic. They were created to address the single-phase ceramic materials’ lack of durability. Ceramic matrix composites use ceramic reinforcement in a ceramic matrix to achieve improved characteristics.
1. Aerospace sector (gas turbines, structural re-entry thermal protection)
Ceramic materials offer unique qualities such as high-temperature capabilities, high stiffness and strengths, and superior oxidation and corrosion resistance, they are becoming increasingly significant in aircraft applications.
When used for high-temperature and ultra-high-temperature ceramics applications, ceramic materials have lower densities than metallic materials, making them excellent candidates for light-weight hot section components of aircraft turbine engines, rocket exhaust nozzles, and thermal protection systems for space vehicles.
Because of their high-temperature capacity (high melting point), high stiffness and strength, and great resistance to oxidation and corrosion, ceramics are key materials for aeronautical applications. Ceramic materials also have lower densities and, as a result, greater specific strengths than metallic materials.
2. The energy sector (heat exchangers, fusion reactor walls)
Ceramic matrix composites (CMCs) are widely employed in the aerospace and energy sectors (gas turbines, structural re-entry thermal protection) (heat exchangers, fusion reactor walls).
Radiant heater tubes, heat exchangers, heat recuperation, gas and diesel particle filters, and components for land-based turbines for power production are only a few examples of products used in the energy and environmental industries.
These applications require a joint either permanent or temporary between CMC components with surrounding materials.
Ceramics have stronger wear resistance, mechanical qualities, and reduced stress on the neighboring tooth at the restoration-tooth margin, which is one difference between ceramics and composite materials. Inlays, cusp coverage restorations such as crowns and on lays, and extremely attractive veneers are all possible with ceramics.
Boat hulls, swimming pool panels, racing car bodies, shower stalls, bathtubs, storage tanks, and imitation granite and cultured marble sinks and countertops are just a few examples of composite materials utilized in buildings, bridges, and constructions. They’re also becoming more common in general-purpose automobile applications.
3. Fiber-reinforcedd carbon/carbon composites (C/C)
Carbon fiber reinforced carbon matrix composites (C/C composites) have developed as one of today’s most advanced and promising engineering materials.
Carbon fibers and carbon matrices are used to make carbon/carbon composites.
To sustain the rigors of harsh environments, carbon/carbon composites utilize the strength and modulus of carbon fibers to reinforce a carbon matrix. Carbon/carbon composites have proven to be reliable and cost-effective in systems, particularly when several components in an assembly may be replaced with a single-piece carbon/carbon composite design.
● Furnace fixturing
The applications for C/C material as fixtures and grids in heat-treating applications are practically endless. Matching the material’s capabilities with the manufacturing need, like with all other advanced technology solutions, is an essential starting point.
● Heatshields
In an inert atmosphere, carbon/carbon (C/C) composites show better high temperature strength. Strength and stiffness, as well as fracture toughness, are all features important to consider. High-temperature oxidation resistance, frictional abilities, and thermal conductivity.
● Load plates
The bending moment is calculated by multiplying the span length by the weight to be supported by eight. The maximum bending moment would be 12 x 600/8 = 900 foot-pounds for a beam spanning a 12-foot room and sustaining a weight of 600 lbs.
● Heating elements
Heat transfer in any composite that consists of an orthogonal arrangement of fibers within a matrix is controlled by the thermal conductivities of the two components, their relative volume fraction, and their geometrical arrangement.
When the matrix contains porosity (cracks or pores), it is necessary to account for a third phase because a pore is a barrier to heat flow, and its presence and distribution has a significant impact on heat transfer. The combination of the solid thermal conductivity and radiative conductivity provides the effective thermal conductivity of the composite C/C as a function of temperature.
● And X-ray targets
Non-destructive processes such as x-ray tomography, which can present not only information about density and porosity but also the 3D vision with identification of closed and open pores, as well as a precise location of these defects, are of great interest to the industry because they can present not only information about density and porosity but also the 3D vision with identification of closed and open pores, as well as a precise location of these defects, are of great interest to the industry.
To clearly highlight cracks and holes, X-ray tomography was employed to reconstruct the microstructure of a carbon/carbon (C/C) composite.
● Rocket nozzles must withstand an extremely rapid temperature increase in a highly corrosive atmosphere while maintaining a high degree of integrity.
The conflict between transport of reaction and heterogeneous mass transfer, associated with reactivity differences between constituent phases, is addressed in the modeling of melting of carbon/carbon (C/C) composites used as rocket engine hot parts.
Carbon/Carbon (C/C) composites have a number of relative advantages, including a high ratio of mechanical characteristics to density at high temperatures, low thermal expansion, and cost-effective manufacturing of small and large parts.
The flow in the core of the nozzle is very turbulent under rocket-firing conditions, and so are the boundary layers. Because of the high temperature, homogenous reactions in the gas phase occur quickly, and the gas mixture is always in a state of chemical equilibrium.
4. Fiber-reinforced polymer matrix composites (PMCs) or polymeric composites
PMCs are made up of a continuous phase of organic polymers and a dispersed phase of reinforced fibers. Fracture toughness, tensile strength, and stiffness are all controlled by the reinforcing fibers.
Polycarbonate, polypropylene, and polyethylene are common thermoplastic materials utilized in the manufacture of medical plastic items, as well as the formulation of specialized polymers to satisfy particular medical device applications.
By providing the following benefits, polymers and polymer matrix composites have helped enhance the quality of healthcare delivery while also saving countless lives: Making it easier to maintain sterility. Polymers make it possible to make affordable, disposable tools and devices including syringes, catheters, and surgical gloves.
● medical devices;
● such as MRI scanners,
● C scanners,
● X-ray couches,
● mammography plates, tables,
● surgical target tools,
● wheelchairs,
● prosthetics.
Why is FRC used?
Fiber-reinforced concrete has higher tensile strength as compared to non-reinforced concrete. It improves the concrete’s long-term durability. It slows the spread of cracks and improves impact resistance.
Fiber-reinforced concrete enhances freezing and thawing resistance. It consists of cement, mortar, or concrete mixed with appropriate fibers that are discontinuous, distinct, and uniformly distributed.
Fibers are commonly used in concrete to prevent cracking caused by shrinkage of the plastic and drying shrinkage. They also limit the permeability of concrete, resulting in less water bleeding.
● Tensile strength
The distribution and orientation of steel fibers inside the concrete matrix determine the tensile behavior of ultrahigh-performance fiber-reinforced concrete (UHPFRC).
The development of ultrahigh-performance fiber-reinforced concrete (UHPFRC) is the result of years of study into how to increase the performance of high-strength concrete in tension.
The presence of steel fiber is the most major element controlling the tensile behavior of UHPFRC. The addition of steel fiber to UHPFRC enhances its flexibility, strength, and fracture resistance.
● Increases the concrete’s durability
The capacity to survive a long time without noticeable degradation is referred to as durability. A long-lasting substance benefits the environment by saving resources, decreasing waste, and lowering the environmental effect of maintenance and replacement.
The development of replacement construction materials depletes natural resources and has the potential to pollute the air and water. Concrete’s durability may be characterized as its capability to handle corrosion, chemical damage, and abrasion while preserving its desired engineering qualities.
● Reduces crack growth and increases impact strength
The cracks are an issue because they allow for the possibility of moisture problems and reinforcement corrosion, which reduces the structure’s load-bearing capability. When concrete cracks, the structure’s durability suffers as well.
In reinforced concrete constructions, crack development is a prevalent issue that reduces the structure’s endurance. When the concrete breaks, the tensile pressures are carried by the tension reinforcement rather than the concrete.
By utilizing suitable reinforcement, crack widths may be restricted, and one option is to combine tensile and crack reinforcement. The purpose of the reinforcement is to spread the fractures over the cross-section, resulting in a large number of minor cracks rather than a few larger cracks.
● Fiber-reinforced concrete improves resistance against freezing and thawing
The freeze-thaw cycle is a primary source of damage to concrete and brick structures. Water fills the gaps in a solid, porous material, freezes, and expands, causing freeze-thaw damage. Only a quality concrete sealer can protect your concrete from freeze/thaw damage.
Types of most often used fibers in FRC
● Sợi thép dùng cho bê tông sợi thép (FRC)
Bê tông xi măng thông thường được biết đến là có tính chất chịu kéo kém, khiến nó dễ bị uốn cong trong các cấu kiện kết cấu. Để tránh hiện tượng nứt bê tông, đặc biệt là trong các công trình chứa nước hoặc dẫn nước, bê tông kết cấu cần được thiết kế thành một khối liền mạch không nứt.
Việc sử dụng sợi thép gia cường trong bê tông giúp nâng cao khả năng chịu lực của các cấu kiện kết cấu trước các áp lực lớn. Sợi thép gia cường bê tông giúp tăng cường độ bền của vật liệu này dưới mọi loại tải trọng. Để nâng cao độ bền kéo trong các công trình bê tông, bê tông cốt sợi thép mang lại khả năng chống nứt và chống lan truyền vết nứt tốt hơn.
Bãi đỗ xe, sân chơi, đường băng sân bay, đường lăn, nhà chứa máy bay bảo dưỡng, đường tiếp cận và xưởng sản xuất đều là những ví dụ về ứng dụng của sàn bê tông sợi thép.
● Sợi PP dùng cho FRC
Đây là một loại polymer tổng hợp có nguồn gốc từ hydrocacbon. Bê tông cốt sợi polypropylene (PPFRC) được tạo thành từ các sợi polypropylene rời rạc có chiều dài rất ngắn, đóng vai trò là cốt thép bên trong nhằm cải thiện các tính chất của bê tông. Khi được đưa vào ma trận bê tông, các sợi này phải được trộn trong thời gian dài hơn để đảm bảo sự phân tán tối ưu của sợi trong hỗn hợp bê tông.
● Sợi macrofiber dùng cho FRC
Sợi vĩ mô, còn được gọi là sợi kết cấu, được thiết kế để chịu tải trọng và do đó được sử dụng để thay thế vật liệu gia cường truyền thống trong các ứng dụng phi kết cấu, cũng như để giảm thiểu hoặc loại bỏ hiện tượng nứt sớm và nứt muộn.
Nếu không có sợi cốt lớn trong công thức phối trộn, các vết nứt này sẽ lan rộng trên bề mặt kết cấu, thường dẫn đến hư hỏng. Khi sợi cốt lớn được đưa vào công thức phối trộn, chúng sẽ liên kết hai bên vết nứt lại với nhau, ngăn chặn vết nứt lan rộng. Thiết kế có gờ hoặc bậc thang giúp tăng cường độ bám dính với bê tông, đó là lý do tại sao nó được sử dụng.
● Sợi PVA dùng cho FRC
Sợi PVA (Polyvinyl alcohol) là loại sợi đơn sợi phân bố đều trong ma trận bê tông, tạo thành một mạng lưới sợi đa hướng giúp kiểm soát sự co ngót, chống mài mòn và bảo vệ khỏi hiện tượng giãn nở và co ngót do nhiệt. Loại sợi này có thể được sử dụng thay thế cho lưới thép hàn và cốt thép làm vật liệu gia cố chính.
● Lưới sợi cho bê tông cốt sợi
Thay vì sử dụng lưới thép, bê tông lưới sợi (còn được gọi là bê tông cốt sợi) sử dụng sợi làm một trong các thành phần của công thức phối trộn. Lưới sợi là giải pháp thay thế mới hơn so với lưới thép truyền thống. Trong quá trình trộn, các sợi này được thêm vào bê tông tươi.
Loại bê tông chứa sợi này được đổ và đông cứng tại công trường theo cách tương tự như bê tông thông thường. Loại bê tông này dễ thi công và đang góp phần cải thiện quy trình thi công sàn.
3 loại sợi nào là tốt nhất cho bê tông?
Sợi vi sợi tổng hợp
Trong 10 giờ đầu tiên sau khi đổ, bê tông sợi siêu mịn chứa sợi polypropylene giúp giảm hiệu quả hiện tượng co ngót sớm. Nguyên nhân là do các sợi này có thể hấp thụ một lượng nước nhất định, từ đó làm chậm quá trình bay hơi. Các sợi này phát huy tác dụng tốt hơn trong việc giảm thiểu các vết nứt do co ngót khi bê tông còn dẻo và thường được sử dụng kết hợp với cốt thép bê tông.
● Để giảm hiện tượng nứt do co ngót của nhựa
Sự bay hơi và sự thấm hút là hai cơ chế khiến bê tông tươi hấp thụ nước, dẫn đến hiện tượng co ngót dẻo. Đối với công trình dự kiến, cần giữ cho tổng lượng nước trong hỗn hợp bê tông ở mức thấp nhất có thể.
Điều này có thể đạt được bằng cách sử dụng tỷ lệ cao các loại cốt liệu cứng, rắn, không bị bám lớp đất sét, cũng như các phụ gia giảm nước thuộc loại trung bình hoặc cao.
Sợi kim loại/Sợi thép
Sàn bê tông cốt sợi thép có thể giảm thiểu các vết nứt trên bê tông đã đông cứng và mang lại khả năng chịu lực tối đa trước các tải trọng lớn, cả động và tĩnh.
Sợi thép mang lại nhiều lợi ích, bao gồm:
1. Bê tông có khả năng chịu tải cao hơn.
2. Độ dày của tấm bê tông đang được giảm xuống.
3. Các vết nứt trên bê tông không ảnh hưởng đến khả năng chịu tải.
4. Độ bền được nâng cao.
5. Chi phí bảo trì thấp
6. Khả năng linh hoạt đã được cải thiện.
Vật liệu sợi kim loại được sử dụng trong các ứng dụng lọc chất lỏng và không khí đòi hỏi khả năng chịu nhiệt và kháng hóa chất cao. Chúng có thể được hàn thành các cấu trúc bộ lọc có độ bền cao. Có sẵn các loại bộ lọc sợi kim loại có thể làm sạch và tái sử dụng. Sản phẩm có nhiều kích thước đường kính khác nhau và được chế tạo từ các loại kim loại nguyên chất và hợp kim đa dạng. Các sợi kim loại này có thể được sử dụng riêng lẻ cho nhiều mục đích khác nhau, hoặc có thể được gia công thành các sản phẩm khác thông qua các quy trình sản xuất dệt may đa dạng.
1. Để kiểm soát độ rộng vết nứt trong bê tông đã đông cứng
2. Sợi tổng hợp cỡ lớn/sợi cấu trúc
Sợi tổng hợp cỡ lớn không bị gỉ.
Do đó, không có vết gỉ nào hình thành trên bề mặt của sợi tổng hợp cỡ lớn. Hơn nữa, khi cho phép biến dạng lớn hơn, sợi tổng hợp cỡ lớn có thể được sử dụng hiệu quả trong các ứng dụng như lớp lót tạm thời cho các mỏ.
1. Để chịu tải và do đó
2. Để thay thế vật liệu gia cố truyền thống trong một số ứng dụng không mang tính kết cấu
3. Để giảm thiểu hoặc loại bỏ hiện tượng nứt nẻ ở cả giai đoạn đầu và giai đoạn sau.
Vậy là hết phần chia sẻ về FRC và các loại sợi. Để đọc thêm các bài viết khác, vui lòng truy cập: https://fiberego.com/blog/.
