Glass fiber manufacturing technology-common glass fiber shapes in composite materials

Finished products such as glass fiber cloth are composed of many fiber bundles, and the glass fiber bundles are composed of many thin fibers. The glass fiber cloth is made of long glass fiber, and the felt is generally made of short glass fiber. Fiberglass cloth can increase tensile strength. Short glass fibers increase their toughness in glass fiber products. Therefore, the strength of glass checkered cloth is higher than that of glass felt.

The weaving method of fiberglass cloth is different, and there are many weaving methods. Plain weave is simple and inexpensive. Compared with other weaving methods, it is not so soft. But it can be combined well in the cutting process.

Fiberglass weave types

Plain weaving of fiberglass woven cloth is made by interweaving warp yarns and weft yarns one after another. Plain weave fiberglass cloth is the cheapest and least soft, but it can be combined well when cut.

Because the warp and weft yarns of the plain weave are interlaced every other one, the same number of warp and weft yarns are arranged in the plane, the number of interlacing is the most, the yarn buckling is the most, and the floating length is the shortest. Make the fabric firm, wear-resistant, stiff and smooth, but with less elasticity and weak gloss. Because the warp and weft yarns are interwoven many times, the yarns are not easy to rely too closely on, so the density of the fabric is generally not too large.

Twill weave of fiberglass woven cloth is a compromise between plain weave and satin weave. Medium strength, not as fast as plain weave. Compared with plain weave fabric, twill weave fiberglass woven cloth has fewer interweaving points in the weaving cycle and has floating long lines. Compared with plain weave fabrics, twill fabrics have higher warp and weft density, soft fabrics and better luster.

Satin fabrics of fiberglass woven cloth. Warp and weft yarns have the least interweaving points and the highest density that can be woven. Satin fabrics are thicker than plain weave and twill weave, with a soft texture and good drape.

In terms of fastness, plain weave is the best, followed by twill weave, and satin weave last. The satin weave is better than twill in gloss, softness and density, and the plain weave is the last.

According to the fiber length, it can be roughly divided into three categories.

Continuous glass fiber or textile glass fiber. The production method is mainly that molten glass flows out through a leakage plate made of high temperature resistant materials, and is formed by drawing multiple fiber bundles with a high-speed rotating drum. After textile processing, it can be made into glass yarn, cloth, ribbon, rope and Twisted roving and other products.

Fixed-length glass fiber or glass long cotton. It is a messy single fiber, which can be made into felt or wool yarn, and wool yarn can also be made into cloth and tape. Fixed-length glass fibers are made by high-speed air-jet blowing or molten glass liquid drawn into fibers and then cut.

Glass wool. Glass wool is a kind of glass fiber with a short fiber length, which is fluffy in shape, similar to cotton wool, and is also called short glass wool. Glass short wool is steam sprayed, centrifugal method, centrifugal spray, flame spray and other methods Processed.

Glass fiber has excellent properties such as small bulk density, low thermal conductivity, good sound absorption, high filtration efficiency, non-combustion, and corrosion resistance. Its long fiber can be woven into glass fiber wall covering, and the glass fiber cloth is bonded by resin and hot pressed. Then it is made into glass fiber reinforced plastic decorative board, and glass wool is processed into glass wool decorative board by hot pressing.

What are the common glass fiber shapes in composite materials?

Glass fiber is currently the most used reinforcing fiber material in polymer matrix composites.

Direct untwisted roving

Direct yarn is a continuous fiber that is directly drawn from glass melt through a single-strand untwisted roving. Generally, the yarn balls are collected into bundles and then packed into pallets.

Main applications: pultrusion, winding, weaving, reinforced thermoplastics (twin-screw machine), LFT.

Fiberglass woven roving

Plyed yarn is a single yarn that passes through a twisting process, and two or more single yarns are combined and twisted together. To be simple, it can be understood that multiple direct yarns are wound into a single strand through a special winding device, which is called ply yarn. The main purpose of stranding is to process the silk cake into the required linear density and shape.

Direct yarn is a one-step method, with high production efficiency, low cost and less hairiness. Plyed yarn is a two-step method. After winding, it has better uniformity and is easy to disperse. It is suitable for the short cut, but has more hairiness.

Tips

How to quickly distinguish between direct yarn and ply yarn?

One strand of yarn is drawn out and shakes quickly. One strand is still direct yarn, and the stranded yarn is split into multiple strands.

Bulked yarn

Bulk yarn is the use of compressed air to impact and disturb glass fiber yarn to separate the fibers in the yarn and increase its volume to become bulky yarn. It not only has the high strength of continuous fiber, but also the bulkiness of short fiber.

Bulk yarn solves the problems of smooth surface, no branching, and easy breaking of traditional glass fiber. Because of its fluffy, softness, large specific surface area, and strong adsorption of binders, it is suitable for manufacturing friction materials. In addition, the bulky yarn has low thermal conductivity and is suitable for insulation materials.

Spun yarn

Spun yarn refers to glass fiber yarn with a monofilament diameter of less than 10 microns, and its common monofilament diameters are 5, 7, and 9 microns. With the development of technology, monofilament diameters of 4 and 4.5 microns have also appeared. According to different purposes, it is divided into electronic yarn and industrial yarn.

Electronic yarn is used to woven into electronic cloth for the manufacture of copper clad laminates. Industrial yarns are mainly used as industrial fabrics, such as fire curtains, timing belts, cords, woven sleeves, etc.

Fiberglass mesh fabric

Fiberglass mesh fabric is a non-twisted roving plain weave fabric. The warp and weft are woven up and down at 90°, and the strength is in the warp and weft direction of the fabric.

Warp knitted axial fabric

The warp-knitted axial fabric is made by warp-knitting glass fiber roving directly on a multi-axial warp knitting machine. The warp and weft yarns are arranged in one or more layers according to a preset angle, and then they are bundled with stitching threads. 

The more common angles are 0°, 90°, 45°, -45°, which are divided into unidirectional cloth, biaxial cloth, triaxial cloth and quadriaxial cloth according to the number of layers.

Since the yarns between the layers are parallel and do not cross, it is conducive to the flow of the resin, and the axial cloth is often used in the closed mold process. Moreover, the yarn is not bent when weaving, the mechanical loss is small, and the strength is higher. There is no obvious fabric impression, so the surface quality of the product is high.

Chopped strand glass fiber yarn

Short cut the glass fiber yarn into a certain length of raw yarn.

Chopped strand glass fiber mat

A chopped strand mat is to chop the glass fiber strands into a certain length (usually 20-50mm), randomly settle on the conveyor belt, and then use powder or emulsion adhesive to bond these chopped fibers together.

We usually say that powder felt and emulsion felt are mainly different in adhesives. The powder felt is relatively soft and has better permeability, but its dry strength is poor. It is not suitable for large products, and it is easy to shed hair and is not friendly to the environment. Emulsion felt is hard and poor in permeability, but has good dry strength, is not suitable for tearing, and is not easy to shed hair, which is environmentally friendly.

Stitched felt

Stitch-knitted mats are made by stitching a certain length of chopped glass fiber raw filaments with non-directional settlement and then stitching them with organic fibers. Comparing the forming of chopped strand mats, the two are very similar. The only difference is that the chopped strands are bonded with an adhesive, while stitch-knitted mats use stitching threads. The stitch-bonded felt has high tensile strength and is not easy to be deformed, and is suitable for a variety of molding processes.

Glass fiber composite felt

Generally speaking, the glass fiber composite mat is made of glass fiber non-twisted roving as a single layer or multiple layers arranged in parallel, and the outermost layer is composite chopped into a certain length of glass fiber yarn, sewn with organic fibers. Simply put, it is axial cloth + stitched felt.

Due to the special requirements of some products, there are also composite felts of checkered cloth and chopped yarn on the market for hand lay-up. However, conventionally speaking, the composite felt is usually referred to as the axial cloth composite chopped yarn.

The composite felt has strong design, which can reduce the layering and improve the production efficiency. The bonding force between layers is good, the fiber is not easy to deform, there is no binder, and it is easy to penetrate.

Continuous glass fiber mat

Continuous felt is a certain number of continuous fibers distributed on the mesh belt in a non-oriented loop, and is combined by the mechanical action between the strands and a small amount of binder to form a felt.

The one-step method is to draw the silk from the kiln and lay it into felt directly through the forming device under the slat. The advantages are low energy consumption, large output, low cost, good interlayer bonding, and better uniformity. The disadvantage is that it is technically difficult and is basically monopolized by Europe and the United States, so it is expensive to sell.

The two-step rule is to first pull out the raw silk, and then spread the raw silk into felt through the equipment. Need secondary processing, high energy consumption and high cost. The bonding force between the layers is poor, the phenomenon of poor bonding is prone to occur, and the uniformity is also poor. Most domestic enterprises adopt the two-step method. In 2013, Jiuding broke through the technical difficulties of the “one-step method” and filled the domestic gap in this field.

The fiber of the continuous mat is continuous, so its mechanical strength is better than the chopped mat. There is no stitching thread, and the surface quality of the product is good. Isotropic, excellent overall performance, suitable for a variety of processes.

Needle felt

Needle-punched felt is a needle punch for the chopped glass fiber felt after carding, and the fibers between the felt layer glass fiber, the felt layer glass fiber and the reinforced glass fiber base cloth are entangled with each other by mechanical methods, and the fiber network can be A felt-like non-woven fabric material made of reinforcement.