As wind turbine blades continue to become longer, lighter, and more structurally demanding, the reinforcement materials used inside the blade must provide a carefully balanced combination of strength, stiffness, fatigue resistance, processability, and weight efficiency. Bi-Axial Fabric, particularly ±45° fiberglass non-crimp fabric, is widely used because its fiber architecture can be matched to the shear and multi-directional loads experienced by composite blade structures.

In modern wind turbine blade manufacturing, bi-axial fabric is not simply a reinforcement textile. Its fiber orientation, areal weight, resin compatibility, stitching structure, and drapability all influence the final laminate performance. Zhejiang Zhenshi New Material Co., Ltd. identifies biaxial fabric as a wind-power reinforcement material and specifically lists the shear web and wind turbine blade shell reinforcement layer among its applications.

What Is Bi-Axial Fabric?

Bi-axial fabric is a multi-directional reinforcement material in which continuous fiber rovings are arranged along two principal directions and mechanically held together by stitching. Unlike conventional woven fiberglass fabric, the main reinforcing fibers are not repeatedly interlaced. This non-crimp structure allows the fiber bundles to remain relatively straight, which is important for transferring loads efficiently through a cured composite laminate.

For wind turbine blades, common configurations include +45°/-45° bi-axial fabric and 0°/90° bi-axial fabric. The appropriate architecture depends on the dominant load path within the blade.

Zhenshi's biaxial fabric is manufactured by arranging non-twisted yarns in +45°/-45° or 0°/90° directions and fixing them with a stitch structure. Depending on the application, configurations with or without chopped strand mat can also be selected.

This gives engineers greater flexibility when designing the reinforcement schedule of a blade shell, shear web, root region, or other composite structure.

How Is Bi-Axial Fabric Structured?

The performance of bi-axial fabric starts with its fiber architecture. Instead of relying on weaving to hold the reinforcement together, continuous rovings are positioned at predetermined angles and stabilized with stitching yarn.

This structure provides several practical advantages during blade production. The fabric can maintain its designed orientation during cutting, handling, lay-up, and resin infusion, while the absence of significant fiber crimp helps preserve the mechanical contribution of the continuous glass fibers.

Another important parameter is areal weight, normally expressed in g/m². A higher areal weight allows manufacturers to build laminate thickness more quickly, while a lower areal weight can provide better conformability around complex geometries.

For example, Zhenshi lists BIAX600, BIAX808, BIAX1000, and BIAX1200 grades, with total nominal area weights of approximately 612, 812, 1012, and 1212 g/m² respectively. The +45° and -45° layers account for the majority of the reinforcement weight, while the stitching system contributes only a small amount.

For blade manufacturers, this means fabric selection can be connected directly to laminate thickness, fiber volume fraction, handling requirements, and production efficiency.

What Do +45° and -45° Fiber Orientations Mean?

The terms +45° and -45° describe the angle of the primary fiber bundles relative to the reference direction of the fabric.

Why are these angles important?

A wind turbine blade does not experience only simple tensile loading. During operation, aerodynamic forces and gravitational effects create bending, torsion, and shear stresses. In structures where shear loading is significant, ±45° fibers are particularly effective because they can carry loads generated by in-plane shear through tension and compression along the fiber directions.

This is why ±45° bi-axial fabric is particularly relevant to shear webs. Instead of trying to resist shear directly through the resin matrix alone, the laminate uses diagonally oriented fibers to create an efficient load-transfer mechanism.

By contrast, a 0°/90° architecture provides reinforcement along the longitudinal and transverse directions and can be considered when the structural design requires more balanced directional properties.

Why Is Bi-Axial Fabric Used in Wind Turbine Blades?

The main reason is simple: wind turbine blades require reinforcement that can efficiently handle complex and changing loads without adding unnecessary weight.

A blade may experience:

• Flapwise and edgewise bending
• In-plane and interlaminar shear
• Torsional loading
• Cyclic fatigue loading
• Local stress concentrations
• Environmental effects over long service periods

A properly designed bi-axial laminate helps distribute these loads through multiple fiber directions.

Zhenshi's Wind Energy Sector emphasizes the role of glass-fiber and carbon-fiber composite materials in achieving the combination of high strength, high stiffness, lightweight construction, and dimensional stability required by modern wind turbine blades.

For large blades, this balance becomes increasingly important. Increasing blade length increases aerodynamic loading and structural demands, so reinforcement materials must provide sufficient mechanical performance without creating excessive mass.

How Does Bi-Axial Fabric Improve Blade Strength and Stiffness?

The mechanical behavior of a composite laminate depends on both the properties of the fiber and the orientation of those fibers.

Glass fibers provide the primary load-carrying capability, while the resin transfers stress between fiber bundles and protects the reinforcement. In a ±45° laminate, the two fiber directions work together to resist shear and off-axis loading.

The fiber grade also matters. Zhenshi's published data show increasing tensile strength and modulus across its E-glass, E7-glass, E8-glass, and E9-glass roving options. For example, its E9-glass direct roving is listed with tensile strength of 3100–3500 MPa and tensile modulus of 100–103 GPa under ASTM D2343 testing.

However, fabric strength alone does not determine blade performance. Engineers also need to consider:

Fiber volume fraction: Too little fiber can reduce structural efficiency, while excessive fiber content can make resin impregnation more difficult.

Resin system: The resin must provide adequate wet-out, adhesion, fatigue performance, and curing compatibility.

Fiber orientation: The reinforcement must correspond to the actual load path.

Laminate thickness: Additional plies can increase stiffness and strength but also increase weight and manufacturing time.

Void content: Poor infusion or incomplete wet-out can reduce the mechanical performance of the final laminate.

Therefore, bi-axial fabric should be selected as part of the complete composite laminate system rather than evaluated as an isolated textile.

Bi-Axial Fabric in Shear Web and Blade Shell Reinforcement

The shear web is one of the most important structural areas where ±45° bi-axial fabric can be used.

Inside a large wind turbine blade, the shear web connects structural regions of the blade and transfers shear loads generated by bending. Because shear stresses are significant in this component, diagonal reinforcement is highly relevant.

Bi-axial fabric can also be incorporated into blade shell reinforcement. Here, its role is to provide additional multi-directional reinforcement and improve the load-bearing capability of the composite skin.

Zhenshi specifically identifies “Shear Web of Wind Turbine Blade Shell Reinforcement Layer” as an application for its biaxial fabric.

The exact lay-up sequence, fiber orientation, number of plies, and material grade should still be determined through the blade manufacturer's structural design and laminate analysis.

Bi-Axial Fabric vs. Woven Fiberglass Fabric

Bi-axial and woven fiberglass fabrics are both reinforcement materials, but their structures are different.

In woven fiberglass fabric, warp and weft yarns pass over and under one another. This interlacing creates fiber crimp, meaning the fibers are not perfectly straight. Woven structures can provide good handling and balanced reinforcement, but the fiber geometry must be considered when evaluating mechanical performance.

Bi-axial non-crimp fabric uses stitched, directionally aligned rovings instead. This allows manufacturers to specify the principal fiber orientations more directly.

For wind turbine blade applications, the key comparison is therefore not simply “which fabric is stronger?” but rather:

Which fiber architecture best matches the load path, manufacturing process, and required laminate performance?

For shear-dominated structures, ±45° bi-axial fabric can be particularly attractive. For predominantly longitudinal blade loads, unidirectional reinforcement may be more appropriate. Zhenshi also supplies unidirectional and carbon-fiber reinforcement solutions for applications requiring higher directional stiffness.