FRP Material

E‑glass fiber‑reinforced polyester laminates — the most common type of FRP composite — combine a density of roughly 1.8 g/cm³ with a tensile strength typically between 200 MPa and 350 MPa. These thermoset materials offer a flexural modulus in the range of 10–20 GPa and a relatively low coefficient of thermal expansion (15–25 × 10⁻⁶ /°C), while absorbing less than 0.5% moisture by mass. Such a balance makes them a go‑to choice for corrosion‑resistant industrial structures, from chemical plant walkways to marine handrails, where weight savings and long‑term durability matter.

Density

A standard E‑glass/polyester FRP laminate has a density of approximately 1.5 g/cm³ to 2.0 g/cm³, depending on the glass content and manufacturing process. Hand lay‑up laminates with lower fiber volume fractions sit near the lower end, while pultruded profiles with higher glass loading can reach 2.0 g/cm³. For comparison, this is roughly one‑quarter the weight of structural steel, which directly reduces transportation and installation costs in field‑erected projects.

Tensile Strength

Typical tensile strength values for E‑glass/polyester systems range from 200 MPa to 350 MPa in the fiber direction (ASTM D638). The exact number depends heavily on fiber architecture — unidirectional fabrics can push the upper limit, while chopped strand mat laminates sit closer to 200 MPa. In real‑world applications, engineers often work with a design tensile strength around 150 MPa to account for long‑term environmental factors.

Flexural Modulus

The flexural modulus (ASTM D790) of standard FRP laminates falls between 10 GPa and 20 GPa. This stiffness is substantially lower than that of steel, but the inherent flexibility can actually be an advantage in applications like grating and decking where some deflection is acceptable and helps distribute dynamic loads without cracking the matrix.

Coefficient of Thermal Expansion

E‑glass/polyester composites exhibit a coefficient of thermal expansion (CTE) in the range of 15–25 × 10⁻⁶ /°C in the fiber direction. Transverse CTE can be higher, typically 25–35 × 10⁻⁶ /°C. This property is critical when joining FRP components to steel or concrete in outdoor structures — the difference in thermal movement must be accommodated through slotted holes or flexible connectors.

Water Absorption

In 24‑hour immersion tests (ASTM D570), E‑glass/polyester FRP typically absorbs 0.1% to 0.5% moisture by weight. This low water uptake preserves mechanical properties in humid or marine environments and is one of the reasons FRP handrail systems and gratings are widely adopted in coastal water‑treatment facilities.