GFRP UD (Unidirectional Glass)
A strong, cheap unidirectional glass-fiber composite
Typical values for the temper in the title
In unidirectional GFRP, glass fibers (usually E-glass) run in one direction. Strength is high (about 1000 MPa in the database), but stiffness is much lower than carbon (about 40 GPa versus about 135), and it is heavier. Advantages: much lower cost, electrical insulation, radio transparency, and slightly higher strain to failure.
It is used for pultruded rods and profiles, leaf springs, concrete reinforcement (instead of steel rebar), electrical insulating rods and antennas.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 1000 MPa | along the fibers |
| Elongation A | 2.5% | |
| Modulus of elasticity E | 40 GPa | along the fibers |
| Density ρ | 1.90 g/cm³ | |
| Compressive strength | 600 MPa | |
| Interlaminar shear strength (ILSS) | 50 MPa | |
| Machinability | Carbide only | relative rating in the site database |
Structure: fiber and matrix
| Feature | Value | Meaning |
|---|---|---|
| Fiber | E-glass | strength, insulation |
| Matrix | polyester, vinyl ester or epoxy | |
| Layup | unidirectional (0°) |
Typical values per producer data.
Constructions and versions
In a composite the "material" is built together with the part: fiber, matrix, ply directions and fiber content are chosen. The same fibers in a different layup give very different properties.
| Version | Properties | When to choose it |
|---|---|---|
| Pultrusion | continuous profiles and rods | rods, profiles, concrete reinforcement |
| Filament winding | tubes and vessels | pipes and pressure vessels |
| S-glass | stronger than E-glass | aerospace and defense |
Applications
- Rods and profiles
- Leaf springs
- Concrete reinforcement
- Electrical insulating rods
- Antennas and radomes
Fabrication
Directionality
Properties along the fibers are very high, and across them much lower (in unidirectional material, tens of times lower). Plies are laid out along the load directions.
Insulation
Electrically insulating and radio transparent, unlike carbon fiber.
Machining
Machine with carbide or diamond tools. Glass dust irritates skin and lungs: extraction and protection.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| CFRP UD (Unidirectional Carbon) | 1500 MPa | Not possible | carbon fiber: stiffer and lighter, expensive · material page |
| GFRP Woven Glass | 350 MPa | Not possible | woven glass fiber: for several directions · material page |
| Basalt Fiber Composite | 1000–1100 MPa | Not possible | basalt fiber: similar, more heat resistant · material page |
Common mistakes
Replacing carbon with glass without checking stiffness
The modulus is about 3 times lower. The part will deflect more.
Applying a high sustained load long term
Glass fibers are sensitive to stress rupture under sustained load.
Machining without protection
Glass dust is an irritant.
Equivalents, standards and supply
| Standards | Test methods: ASTM D3039 / D3410 / D2344 |
|---|---|
| Forms | prepreg · Filament Wind |
| Producers | Owens Corning · AGY |
Learn more
Values are typical and for comparison only. In composites, properties depend strongly on fiber direction, fiber content, layup and process. For design, rely on data for the specific laminate and tests. The standards mentioned are mainly test methods (ASTM D3039, D3410, D2344 and others). Sources: producer data and the METAL HUB materials database.
Updated: October 31, 2026