Fiberglass untwisted roving: How to scientifically select the substrate for composite material reinforcement?

Untwisted fiberglass roving is a key reinforcing material in the field of composite materials, and its properties and applications vary significantly depending on the classification method. It can be mainly classified from three aspects: weave structure, yarn reinforcement direction, and fiber chemical composition.

 

01 Classification by Weave Structure

 

The weave structure directly affects the physical properties and processing adaptability of the fabric:

 

1. Plain Weave Fabric:

 

Uses a plain weave (1/1), with warp and weft yarns interlacing alternately. The number of interlacing points (ng) in a complete weave cycle is 2, the highest among the three. This makes its structure dense, the fabric stiff, flat, and not easily deformed. It is mainly used to reinforce fiberglass products with flat surfaces or small curvatures (such as sheets, flat structures). If used for products with complex shapes and large concavities/convexities, it is prone to wrinkling.

 

2. Twill Weave Fabric:

 

Uses a twill weave (such as 1/2, 2/1, 2/2, etc.), with warp or weft floats arranged in a stepped pattern, forming a continuous diagonal texture on the fabric surface.

 

3. Fiberglass roving:

 

The number of interlacing points (ng) within a complete weave cycle is 3 or 4, lower than that of woven fiberglass. Therefore, its warp and weft yarns have less crimp, resulting in a relatively loose, soft structure that is easily deformed. This characteristic gives it excellent moldability and formability when manufacturing fiberglass products with complex shapes and high curvature (such as ship hulls and complex shells), and it is less prone to wrinkling.

 

4. Satin weave:

 

It is characterized by at least 5 interlacing points (ng≥5) within a single complete weave cycle. This structure results in longer yarn floats and a smoother fabric surface, but its application in fiberglass roving fabrics is relatively limited.

 

Synergistic effect of weave structure and fiber diameter:

 

The moldability of a fabric depends not only on the weave structure but also closely on the diameter of the fiberglass used. The diameter of fiberglass used to produce roving typically ranges from 12 to 24 μm. Larger diameters result in stiffer roving fabrics; finer diameters result in softer roving fabrics with better moldability.

 

02. Classification by Yarn Reinforcement Direction

 

The strength of untwisted roving is mainly concentrated in the warp (length direction) and weft (width direction) of the fabric:

Standard bidirectional fabric: The warp and weft yarn densities are basically balanced, providing reinforcement in two main directions.

 

Unidirectional fabric: Designed to meet high strength requirements in a specific direction. By concentrating a large number of untwisted rovings in the warp or weft, the strength and modulus in that direction are significantly improved, forming a warp-unidirectional or weft-unidirectional fabric. This type of fabric is often used in structural components that need to withstand high loads in a specific direction.

 

03. Classification by Fiber Chemical Composition

 

The chemical composition of the glass fiber matrix determines the mechanical properties and environmental resistance of the roving:

 

1. Alkali-free glass fiber untwisted roving (alkali-free woven fabric): Made of E glass fiber. Compared with medium-alkali fabric, it has higher strength, higher modulus, and better weather resistance, water resistance, and alkali resistance. 1. **Using Fiberglass Reinforced Plastic (FRP) Fabric:** This is the preferred choice for manufacturing high-end FRP products requiring long-term durability and reliability, such as those for ships, pressure pipelines, and fan blades.

 

2. Medium-Alkali Glass Fiber Untwisted Roving Cloth (Medium-Alkali Woven Cloth/Fabric): Made of C-type glass fiber. It has poor water resistance but good acid resistance. It is mainly used in acidic corrosive environments, such as linings of certain chemical storage tanks and filter materials for acidic media.

 

3. Alkali-Resistant Glass Fiber Untwisted Roving Cloth: Produced using special alkali-resistant glass fibers (such as AR glass fiber). This fabric has superior alkali and water resistance compared to alkali-free glass fiber cloth and is specifically designed for long-term exposure to strongly alkaline environments (such as reinforced concrete and GRC products).

 

4.High-Strength/High-Modulus Glass Fiber Untwisted Roving Cloth:

 

Made using special glass fibers such as S-type glass (high strength) or HMG (high modulus). In cutting-edge applications requiring extreme strength, stiffness (modulus), or impact resistance (such as aerospace, high-performance sports equipment, and bulletproof armor), its performance far surpasses that of ordinary E-grade fiberglass cloth.

 

The versatility of untwisted fiberglass rovings allows them to meet the wide range of application needs in the composite materials industry.

 

Understanding their classification by weave structure (grid, twill, satin), reinforcement direction (biaxial, uniaxial), and chemical composition (alkali-free, medium-alkali, alkali-resistant, high-strength/high-modulus) and their corresponding core characteristics (such as stiffness, moldability, strength directionality, and corrosion resistance) is crucial for scientific material selection and optimizing product performance and processes. Only by comprehensively selecting the most suitable type of untwisted roving based on the structural complexity, stress state, and usage environment of the final product can the optimal balance between material performance and cost-effectiveness be achieved.