What is a bidirectional glass fiber and glass wrap?
GFRP bidirectional glass wraps are actually reinforcing fabrics consisting of glass fibers that have higher performance and strength without any higher weight or thickness than unidirectional glass fibers. Glass fiber fabric has been used for a long time under various forms and it has been the most widely used type of reinforced composite. These fabrics are produced in a variety of different types; The versatility of glass as a fiber makes it unique industrial textile material. the Woven form offers a combination of properties from high strength to fire resistance at an affordable cost. The yarn sizes and weave patterns provide numerus design potential allowing the end user to choose the best combination for material performance, economics and flexibility.
The fiber and glass wrap of the Afzir company are woven in a wide range of weights from 200 grams to 900 grams of fibers. These glass fibers can be combined with a variety of resins such as polyesters or epoxy to produce a rigid plastic/GRP/fiberglass composite reinforcement.
bidirectional glass wrap is suitable for use in methods like wet lay-up, vacuum bag and resin injection (common resins such as epoxy, polyester and vinyl ester) and can even be used alone as reinforcement in molds or fiberglass / GRP.
It also combines them with other reinforcements such as carbon fibers or more synthetic laminated fibers with special properties. It can be used as a lightweight bidirectional glass fabric in RC wings and fuselages, car panels, surfboards, boats and molding. Bidirectional glass fibers are often a great alternative to traditional short-fiber (CSM) fabrics, especially when working with epoxy resin, where the lack of adhesive will damage the work.
Types of bidirectional glass fibers
Bidirectional glass fibers are available in different types, which are used according to the needs of projects:
Class E glass fibers
Class C glass fibers
Class A glass fibers
Class S glass fibers
Type E glass fibers are the most common glass fibers with the least alkali used in their manufacture. In addition to retrofitting structures, these fibers are also used in the electrical industry as electrical resistors. Type C is widely used in environments where corrosive chemicals exist. Type A glass fibers are out of production today. S-type glass fibers have high strength and modulus of elasticity and are mostly used in aerospace industry and aerospace research to cover missiles and aircraft parts.
Application of bidirectional glass wrap
The main applications of bidirectional glass wrap are retrofitting and repairing of pipes and tanks, historical buildings, arches, tunnels and highways, and reinforcement of surfaces damaged or damaged by fire, or life span of the structure. Glass fabric increases the seismic resistance and load capacity of masonry or concrete shear walls, beam and column joints and concrete columns, and it compensate the lack of bearing capacity of concrete beams, slabs, columns and walls due to design problems in structures.
The use of bidirectional glass wrap in high-performance structural laminates, while not increasing the weight or thickness of the laminate, improves its hardness.
The superior feature of GFRP bidirectional glass fabric, namely its complete electrical resistance and electrical insulation, has led to its use as a reinforcing material in high-pressure laminates (HPL) in printed circuit boards (PCBs). These PCBs are mainly used in computers, modems, automobiles and telecommunication products. As a result, the demand for fiberglass fabrics in the applied industries has also increased.
The difference between bidirectional glass fabric and bidirectional carbon fabric
- Glass fabric has a lower tensile modulus than carbon fabric.
- The specific gravity of glass fabric is less than that of carbon fabric.
- Glass fabric has lower fatigue resistance than other FRP fabrics.
- The glass fabric is very hard and slows down the cutting tool.
- Glass fabric is cheaper than carbon fabric.
- The tensile strength of glass fabric is half that of carbon fabric.
What is the purchase price of bidirectional glass fabric?
The price of it (code G BGW) is calculated in meters. For getting more information on how to buy and the current price of bidirectional glass fabric, you can contact our experts.
Specifications of bidirectional glass wrap
In bidirectional glass fabrics, the warp and the weft are perpendicular to each other. Therefore, they have higher tensile strength than steel. Their tensile modulus is about 70 GPa. As a result, GFRP composite fabrics can be used as an external reinforcement. Of course, it should be noted that these fibers should not be used as reinforcement in cases where compressive stresses are applied. They are also highly resistant to corrosion and acidic environments.
Some parameters must be taken before buying glass fiber:
- Soft or denier fibers
Denier is a measurement of linear density expressed in terms of grams per 9000 meters and is used to express the softness of fibers.
- Fabric weight
Fabric weight is the weight per unit area of fabric and textiles.
- Overall thickness
Overall thickness is also measured by a gauge with two flat cylinders. Fabric thickness is measured for one area of the specimen by a constant-force spring loading mechanism.
- Overall width or OD
The total width or outside diameter (OD) is the cutting width of a roll of fabric or textile.
- Overall length
Fabrics and textiles are sold in rolls of different lengths, the amount of which depends on the customer’s order.
- High strength fabric
- low weight fabric
- Ambient temperature cured fabric
- Non-corrosive glass fiber wrap
- Flexible fabric
- Glass fabric with low aesthetic impact.
- Glass fiber wrap implemented with various finish
- Seismic retrofitting and structural strengthening
- Increasing load carrying capacity of structural components
- Damage repair of structural elements
- Defect remedial operations
- Mitigation of blast effect on structures.
- Retrofitting of bridges and silos
- Sealing of tanks and industrial coatings and FRP lining
- Manufacture of GFRP composite components
- Weights 100-1200 grams per square meter and width 50-100 mm
Primary Fiber Direction
0° and 90°
Comparison of properties of bidirectional glass fiber with conventional construction steel
|Tensile Strength||2500 MPa||
|Tensile Modulus||70 GPa||
In general, the reinforcement of structures is done in order to increase the bearing capacity of the building, improve the defects caused by corrosion and erosion, increase the ductility of the structure, the need to change the use of the structure and compensate for design and execution errors.
bidirectional glass fibers are corrosion resistant and have high tensile strength, and its low weight, which is one of the goals of retrofitting, has led to an increasing use of them in seismic retrofitting and improvement projects.
In order to perform reinforcement in projects, it is necessary to thoroughly examine the current condition of the structure, such as the current bearing capacity of the elements, defects, the calculation files of the structure, and the existing documents and drawings of the structure.
General principles of bidirectional glass fiber reinforcement system design
General principles and general design method are based on the limit state to provide an acceptable level of performance and safety, and due to less knowledge of FRP composites than other available materials such as concrete, it is necessary to apply strength reduction coefficients. So that the design reliability coefficient is more than 3.5. It is also necessary to measure the properties of existing materials such as compressive strength, modulus of elasticity and… by tests such as core drilling and compressive strength testing and ultrasonic testing.
Types of behavior of bidirectional glass fibers
Tensile behavior of bidirectional glass fiber
Under direct tensile loading, the carbon fibers have no plastic behavior before rupture. The tensile behavior of materials is characterized by an elastic linear stress-strain relationship until sudden failure occurs. Tensile strength and hardness of materials depend on several factors. Since fibers play an essential role in bearing in FRP composite, the type of fibers, orientation and also their amount of them play the most important role in tensile properties.
Compressive behavior of components reinforced with bidirectional glass fibers
bidirectional glass fiber that acts as an outer covering should not be used as a compression reinforcement. However, in columns, due to the confinement behavior of compressive resistant fibers and the capacity of the column increases indirectly.
Evaluation and acceptance
To evaluate the FRP system, the direction of the fibers, the presence of layer separation and adhesion to the surface, the location of the layers and… and Also, the compliance or non-compliance with the design drawings should be checked by the supervisory body, which we will refer to some of the cases and tasks of the supervisory body.
To use bidirectional glass fiber in projects, these materials must be controlled based on laboratory information about these materials. Laboratory information is provided by the supplier company.
After installing and obtaining the strength of CFRP composites, the adhesive tensile test (Pull-Off test) is performed on the core samples and the adhesive resistance must be more than 1.4 MPa to observe the phenomenon of separation and rupture in concrete. If the strength is less than the specified value or the FRP system separates from the concrete, it indicates that the system is defective and the carbon fiber cannot provide the expected performance.
To evaluate and approve the installed fibers, other things should be considered, some of which we will mention:
- Occurrence of separation phenomenon
- For the placement of the layers, the direction is very important and the presence of deflection even by 5 degrees from the specified direction can have a great impact on reducing resistance.
- Thickness after curing with resin
- The length of the fiber splice
Bidirectional glass fibers are one of the most used industrial materials up to now. The mechanical properties of this product are comparable to fibers such as carbon fibers and polymers.
In general, the purpose of retrofitting is to increase the tolerance of the structure against various forces, especially earthquakes. Of course, the purpose of retrofitting is not always to increase the resistance of the structure to earthquakes and can have other causes such as change of use of a building and reduced the quality of materials. Building retrofitting can be considered in two types of buildings:
- Existing and in use buildings
- Earthquake-damaged buildings
Since the demolition and replacement of existing buildings with the new ones is very costly and time-consuming, so the importance of retrofitting buildings is increasing day by day.
Requirements for retrofitting in the building
In the following, we refer to the cases that in case of any of them, we need to present a plan and implement retrofitting in the building:
existing damage in old building
One of the most common cases in buildings is damage and defects during the use of the building. These damages can be seen in different forms in buildings. honeycombing, abnormal cracks and corrosion of rebars in beams, columns and roofs can be considered as common failures in concrete buildings, although many of these cases are not easily detected and Need to perform various methods of concrete testing, including corrugation, rebar scanning and …
Mistakes that occur during the implementation phase need to be investigated by retrofitting experts. These errors can occur in many different ways in different buildings, such as weakness in concrete test specimens, inconsistency of concrete design strength with existing strength, beam and column buckling, honeycombing, and so on.
Change of use of a building
These days, Changes in the use of buildings are common and are among the cases in which the building must be thoroughly examined by experts before doing so. Changes in the use of the building create new forces in the members of the building for which the building is not designed, and their emergence may cause severe breakage and damage to the load-bearing members such as beams, columns and… In these cases, it is necessary for the experienced consulting engineer to fully evaluate the existing structure and perform the feasibility of change of use in order to finally provide a plan with high accuracy and complete details.
detection of defects in a proper time and choosing the right solution will save a lot of building costs. Since choosing an inappropriate method of strengthening, repairing or retrofitting a structure can even make matters worse, it is necessary to seek the help of experienced and expert people in this field.
As there are various retrofitting solutions, employers also have different options for it and they must choose one of these methods to implement in their projects. Reinforcement using unidirectional carbon fiber is a method that is becoming more and more widely used. But what are the most important reasons for the pervasiveness of unidirectional carbon fiber retrofitting?
high resistance, low weight, Lack of conductivity of electricity, reduction in costs and…
There are also problems that other common methods of retrofitting, such as steel and concrete jackets, create for the building, such as weight gain, changes in architecture, disruption of long-term use of buildings, rising costs, and so on. The possibility of recurring problems such as corrosion and rust all add to the benefits of reinforcement using bidirectional carbon fiber.
The details of the implementation of bidirectional glass fibers depend on the geometry of the structure, the smoothness of the substrate and so on, and It is necessary for the contractor to use FRP materials in accordance with the specifications described by the consulting engineer, such as type of fibers, type of resin, number of layers, method of execution and… in performing reinforcement operations.
Steps of implementing bidirectional glass fibers
glass fiber retrofitting systems should be implemented according to the following steps and carefully to achieve the desired quality.
Concrete repair and substructure preparation
It is necessary to eliminate all the defects in the main concrete and the underlying concrete, which may affect the integrity of the CFRP composite, before applying the fibers, and also in cases where there is a possibility of corrosion and rust of the rebars in the concrete, Corrosion and sediments should be cleaned and damaged.
Mixing of resins should be done according to the procedure recommended by the manufacturer in accordance with the technical specifications of the project. All resin components must be mixed at a suitable temperature and in sufficient quantity until the material
A variety of methods for installing bidirectional glass fibers
After preparing the substrate, it is time to install FRP fibers, which have different methods and the installation method must be specified by the consultant. Here are some ways to install FRP fibers:
bidirectional glass fiber wet gluing system
In this installation method, the fiber system is installed by hand without corrosion or dry resin. The fibers can be fertilized and impregnated in a separate process with the help of a device impregnated with resin materials and then installed on the concrete surface.
Pre-impregnated fiber system
bidirectional pre-impregnated systems are first impregnated with resin at the factory, but the resin is not cured. These fibers are bonded to surfaces with or without additional resin and cured on site.
Failure to comply with any of the above and other cases expressed by the consultant and the manufacturer will cause a weakness in the bearing of the system and in some cases the fibers will be separated from the surface. Fibers will prevent:
- Avoid sticking bidirectional glass fiber on the inner surface of the corners as much as possible and observe sufficient development length
- overlap should be applied to the patched areas
After the implementation of the FRP system, it is necessary to implement quality assurance and control programs and programs by the quality control unit (QC). Quality control should be done through a series of required inspections and tests.
Quality control inspectors should be fully familiar with the FRP system and how to implement and install it, and during the installation of the unidirectional glass fiber system should conduct daily inspections, which should include the following:
- Ambient temperature, relative wetness and weather conditions
- The dryness of the surfaces
- Surface preparation methods
- Observe the resin curing process
- The position and size of any layer separation or the presence of air bubbles
The quality control unit should also periodically inspect and evaluate the implemented CFRP composite.
Types of FRP system evaluation methods
With general visual inspections, any changes in color, fiber separation, cracking are examined, and the presence of any of these factors indicates a weakness in the system and improper execution. The nature of FRP composite materials is such that they should never or very rarely be repaired during operation, so surfaces covered with FRP materials should be generally monitored and inspected.
One of the common failures in FRP systems is the separation of concrete composite materials, which is a very dangerous failure that if it occurs, the FRP system is practically inefficient. Therefore, the separation of concrete composite materials should be evaluated. The best way to diagnose this condition is to perform a pull-off test, which should be done at regular intervals according to the regulations. Make a correction for it. If minor damage to the composite material is detected, it can be repaired by methods such as resin injection with caution so that the material is not further damaged. If general and more significant damage, such as scaling or separation of layers, occurs on a large scale, adhesives and composites may need to be removed. Defective materials are removed from the concrete surface on a large enough surface and the cleaned part is re-coated with new materials.
Long-term monitoring and inspection
According to the monitoring and inspection system, like all structural members, the reinforcement system with unidirectional glass fiber must be monitored and inspected. Such measures for bridges are usually carried out once a year in general and every six years in detail, but regular inspections of buildings are rarely carried out. Building quality control engineers need to justify regular monitoring and inspection of reinforced members, and CFRP composite reinforced buildings should be regularly monitored and inspected for reinforced members.
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Frequently Asked Questions
What are bidirectional glass fibers?
Double-sided fiberglass fabrics are made from high-strength fiberglass liners that are interwoven in the form of blur (0 and 90 degrees). Bidirectional fiberglass fabrics are compatible with resins such as epoxy resin, vinyl ester resin and polyester resin. Combining this type of fabric with compatible resins can provide parts or composites with excellent mechanical properties, in addition to the two-dimensionality of the fibers in these fabrics, the mechanical properties of the fibers are provided at distances of 0 and 90 degrees.
What is the brand of bidirectional glass fibers?
The brand of each product is determined by the manufacturer. The brand of bidirectional glass fibers is usually abbreviated to English. For example, double-sided glass fibers are known in Afzir Retrofitting Company under the trade code BGWTM.
What is the special advantage of bidirectional glass fibers?
The special advantages of these fibers include high tensile strength, reasonable price compared to other fibers, high chemical resistance, low weight, high heat resistance, etc.
What is the price of bidirectional glass fibers?
The price of bidirectional fiberglass fabric is lower than that of carbon fiber fabric. Because it has relatively less technical specifications than carbon fiber fabrics. The price of bidirectional glass fibers is determined based on the required weight and dimensions. Due to market fluctuations, it is not possible to offer a single price. For this purpose, to inquire about the daily price of the product, you can contact our experts in Afzir Company.
What are the uses of bidirectional glass fibers?
bidirectional glass fibers in seismic reinforcement and improvement of buildings, retrofitting of industrial structures, retrofitting of bridges and silos, retrofitting of pipes and tanks, sealing of tanks and industrial coatings, manufacture of FRP composite parts, etc...
How to make bidirectional glass fibers?
bidirectional fiberglass fabrics can be sourced from companies that provide reinforcement materials, such as Afzir company.
What is the type of glass used in bi-directional fiberglass fabrics?
bidirectional fiberglass fabrics are widely produced with E-Glass. But it can be made according to customer needs with types of glass type A, type AR glass, type S glass and type C glass.
What surfaces are bidirectional glass fibers compatible with?
bidirectional glass fibers are compatible with surfaces such as concrete, steel, wood and plastic and are well installed on them.
In what dimensions and weights is bidirectional fiberglass fabric available in the market?
bidirectional fiberglass fabrics are marketed in weights of 200 to 1200 g per meter and in widths of 50 to 100 cm. In general, heavy glass fibers are heavier than carbon fibers.
What resins are bi-directional glass fibers compatible with and in what ways can they be applied?
bidirectional fiberglass fabrics are compatible with resins such as epoxy resin, vinyl ester resin, polyester resin, phenolic resin and polyurethane resin. Double-sided fiberglass fabrics can be made by methods such as pre-impregnated system, wet gluing system, resin transfer molding system, compact molding system, etc.