As the global composites sector pushes toward lighter, stronger, and more cost-efficient structures, bi-axial fabric (also written biaxial fabric) has emerged as one of the most strategically important reinforcement textiles available today. Used extensively in wind turbine blade manufacturing, marine hulls, automotive body panels, and structural building components, bi-axial fabrics deliver a unique combination of multi-directional load resistance, excellent drapeability, and process compatibility that unidirectional fabrics alone cannot match.

This article offers a thorough technical examination of bi-axial fabric — covering fiber architecture, stitch geometry, mechanical performance data, standard specification grades, test methods, and the applications where these materials offer decisive advantages.

What Is Bi-Axial Fabric? Definition and Fiber Architecture

Bi-axial fabric is a type of non-crimp fabric (NCF) in which two layers of continuous, non-twisted glass rovings are stacked at defined angular orientations and then bound together by a lightweight polyester stitching yarn rather than by weaving. Because the fiber bundles are never interlaced — they simply lie straight — they retain nearly their full theoretical tensile strength, unlike woven fabrics whose yarns bend at each interlacing point, creating stress concentrations that reduce composite performance.

The two dominant configurations offered by leading manufacturers such as Zhejiang Zhenshi New Material Co., Ltd. are:

±45° (Shear-optimised): One layer runs at +45° to the machine direction; the other at −45°. The result is a laminate ply with maximum in-plane shear stiffness — exactly what is needed in the shear web of a wind turbine blade or the side panels of a load-bearing beam.

0°/90° (Balanced tensile): One layer is aligned with the machine direction (0°); the other runs perpendicular (90°). This configuration maximises both longitudinal and transverse tensile stiffness simultaneously, making it the preferred choice for flat structural panels and boat hulls where loads arrive from multiple directions.

Manufacturing Process: From Roving to Finished Fabric

The production of high-quality bi-axial fabric involves a tightly controlled multi-stage process. Understanding each stage is important for quality engineers evaluating suppliers.

1. Roving Selection and Incoming Quality Control

The base material is direct roving — a bundle of continuous glass filaments wound without twist. At Zhenshi, four glass grades are used, spanning E-Glass through E9-Glass. Each grade undergoes incoming inspection to ASTM D2343 (for direct roving tensile properties) before entering production. Roving linear density is held within ±2% of nominal tex to ensure consistent fabric areal weight.

2. Fiber Spreading and Layer Placement

Rovings are spread from creels onto a flat conveyor at controlled tension. For ±45° fabrics, two independent creel sets are inclined symmetrically to the machine centerline. Automated tension-control systems prevent inter-roving gaps or overlaps, which would create resin-rich zones and stress concentrations in the final laminate.

3. Chain-Lock Polyester Stitching

A warp-knitting machine (typically a Raschel-type loom) passes a fine polyester yarn through both fiber layers in a chain-lock stitch pattern. The stitch weight is kept minimal — typically 6 g/m² — to avoid acting as a barrier to resin flow during infusion. Stitch row spacing and loop size are engineered to hold the fiber architecture during handling without causing localised fiber distortion that would reduce composite mechanical properties.

4. Optional Chopped Strand Mat (CSM) Backing

For applications requiring isotropic surface reinforcement or improved surface finish, a layer of chopped strand mat can be stitched to one face of the bi-axial fabric. The CSM layer also promotes resin flow distribution during vacuum-assisted resin transfer moulding (VARTM), reducing infusion time and void content.

Standard Specifications and Areal Weight Grades

Areal weight (g/m²) is the primary specification parameter for bi-axial fabrics because it directly controls laminate thickness per ply and fiber volume fraction in the cured composite. Zhenshi's standard product range for bi-axial fabrics covers four key grades, all manufactured with the ±45° architecture and a nominal polyester stitch weight of 6 g/m²:

The thin 0° and 90° interlayers (2 g/m² each) serve not as structural plies but as alignment aids that stabilise the ±45° rovings during stitch-bonding, preventing migration during infusion. This architecture is confirmed by Zhenshi's product page for Biaxial Fabrics, which specifies that +45° and −45° layers each carry approximately equal weight — confirming a truly balanced, symmetrical layup.

Heavier grades (BIAX1000, BIAX1200) are preferred where thick plies need to be built up quickly with fewer layup operations — a critical productivity consideration in large wind blade manufacturing. Lighter grades (BIAX600) offer finer drapability for complex double-curved surfaces such as root reinforcement zones and trailing edge strips.

Glass Fiber Grades: E-Glass to E9-Glass

Not all bi-axial fabrics are equal — the mechanical performance of the finished composite depends critically on the glass fiber grade used. Zhenshi offers four glass grades for its bi-axial product line, each tested under standardised protocols to provide reliable design data:

The progression from E-Glass to E9-Glass reflects advances in glass composition, filament diameter control, and sizing chemistry. E9-Glass achieves roughly 59% higher tensile strength and 27% higher modulus than standard E-Glass in direct roving form. For wind power applications, selecting E9-Glass in a BIAX1000 or BIAX1200 construction can meaningfully reduce blade weight while maintaining — or exceeding — structural targets, directly improving turbine annual energy production (AEP).

Mechanical Performance: Key Properties and Testing Standards

The five core mechanical properties cited in Zhenshi's product data for bi-axial fabrics are:

1. Light weight: Despite high structural efficiency, NCF-based bi-axial fabrics produce composites with very low structural weight, enabling weight-optimised structures in wind blades and vehicles.

2. High strength: Straight-fiber architecture ensures full translation of roving tensile strength to the composite laminate with minimal knockdown from crimp. Testing standards include ASTM D2343 (fiber/roving) and ISO 527-5 (UD composite laminates), both of which are reported in Zhenshi's specification tables.

3. Durability: The glass fiber chemistry and epoxy-compatible sizing used in Zhenshi rovings provide long-term resistance to fatigue, moisture ingress, and UV degradation when encapsulated in an appropriate resin matrix.

4. Impact resistance: The multi-directional fiber architecture of a bi-axial ply resists delamination propagation under impact loading more effectively than unidirectional laminates, which tend to split along the fiber direction.

5. Excellent shear, bending, and tensile properties: The ±45° orientation is uniquely suited to maximise in-plane shear modulus. Modelling and experimental data consistently show that ±45° laminates achieve in-plane shear stiffness values 3–4× higher than equivalent 0°/90° laminates of the same areal weight.

Primary Applications: Where Bi-Axial Fabric Delivers Maximum Value

Wind Turbine Blade Shear Webs and Shell Reinforcement

The most demanding and highest-volume application for bi-axial fabric is the shear web of large wind turbine blades. The web is the vertical structural element that resists the shear forces generated by the aerodynamic bending loads on the blade. A shear-dominated structure demands ±45° fiber orientation — which is precisely the primary configuration of bi-axial NCF. Zhenshi's product page explicitly identifies the "Shear Web of Wind Turbine Blade Shell Reinforcement Layer" as the primary scope of application for its biaxial fabrics.

For more on wind power composite solutions at Zhenshi, including spar caps, trailing edge reinforcements, and root inserts, visit the dedicated wind energy application section.

Transportation and Automotive Structures

In the transportation sector, bi-axial fabrics are used in bus body panels, rail car floors, truck cab reinforcements, and boat hulls. The ability to orient fibers precisely at ±45° or 0°/90° allows engineers to tailor stiffness and strength to the exact load case of each structural zone, achieving mass savings of 30–50% versus equivalent steel fabrications.

New Energy Vehicles (NEV)

Battery enclosure structures, under-floor shields, and body-in-white reinforcements for new energy vehicles are increasingly specified with bi-axial glass or carbon fiber NCF. The combination of low areal density and high in-plane stiffness reduces vehicle mass while meeting crash and NVH (noise, vibration, harshness) targets.

Solar and Photovoltaic Structures

Mounting frames and tracking system components for solar photovoltaic installations benefit from bi-axial composite profiles with balanced stiffness in both the length and cross direction, resisting wind uplift and gravity loads simultaneously. Pultruded profiles reinforced with bi-axial NCF substrates are a growing segment of this market.

Building Materials and Civil Engineering

Façade panels, structural insulated panels (SIPs), and external reinforcement wraps for concrete columns all utilise bi-axial fabrics. The building materials and home decoration application area at Zhenshi covers products engineered specifically for these construction-grade requirements.

Process Compatibility: Infusion, Prepreg, and Hand Layup

Bi-axial NCF fabrics are compatible with all major composite manufacturing processes, though the process choice significantly affects achievable fiber volume fraction and void content:

Vacuum-Assisted Resin Transfer Moulding (VARTM / VARIM): The open non-woven structure of NCF allows rapid resin flow through the thickness and along the fabric plane. Combined with a flow medium, VARTM on bi-axial stacks typically achieves fibre volume fractions of 50–58% and void contents below 1% — meeting GL and DNV structural certification requirements for wind blades.

Resin Transfer Moulding (RTM): Closed-mould RTM with bi-axial NCF preforms delivers excellent surface quality on both faces and consistent fibre volume fractions above 55%, suitable for automotive structural parts.

PCM (Pre-impregnated Composite Moulding): Zhenshi also manufactures PCM pre-impregnated products, where bi-axial fiber architectures can be pre-combined with resin for high-rate compression moulding processes.

Hand Layup / Wet Lamination: Though less efficient, bi-axial fabrics can be used in manual wet layup for repairs, prototyping, and lower-volume marine applications, particularly where CSM-backed variants improve resin saturation uniformity.

Comparison with Related Products: When to Choose What

Bi-axial fabric is one of several reinforcement textile formats offered by Zhenshi. Selecting the correct product type for a given structural requirement requires understanding the trade-offs:

vs. Unidirectional (UD) Fabric: UD fabric (see Zhenshi's full fiber fabric range) delivers maximum stiffness along one axis but has minimal transverse properties. UD is the first choice for spar caps where the dominant load is spanwise bending. Bi-axial fabric is preferred wherever shear or bi-directional loading governs.

vs. Tri-Axial and Quadri-Axial NCF: For applications requiring quasi-isotropic in-plane properties, tri-axial (0°/+45°/−45°) or quadri-axial (0°/+45°/90°/−45°) NCFs reduce ply count. However, bi-axial fabrics remain the preferred choice where the structural analysis shows clear dominant load directions, because they allow precise laminate optimisation.

vs. Pultruded Plates: Where extreme compression stiffness is required — particularly spar cap substitution or structural beam flanges — Zhenshi pultruded plates offer higher fiber volume fractions and tighter dimensional tolerances than fabric-based laminates. The two product families are frequently combined in the same structure.

About Zhejiang Zhenshi New Material Co., Ltd.

Zhejiang Zhenshi New Material Co., Ltd. is a specialist manufacturer of polymer composite materials headquartered at No.1 Guangyun South Road, Tongxiang Economic Development Zone, Zhejiang Province, China 314500. The company's product portfolio spans the full composite value chain — from fiber fabrics and pultruded structural profiles through composite frames, PCM prepregs, SMC compounds, and BMC compounds.

The company serves five primary end-use sectors: wind power, solar photovoltaics, new energy vehicles, building materials, and transportation. Its global business layout and vertically integrated manufacturing capabilities make it one of China's recognised suppliers for high-performance glass fiber composite reinforcements.

For technical enquiries about bi-axial fabric specifications, custom areal weights, or glass grade selection, contact the Zhenshi technical team via the contact page or download the product brochure. Product demonstration videos are available at Zhenshi product videos.