Service life and cost performance of glass fiber reinforced plastic (FRP) composites depend on good design and judicious selection of materials and processes. In FRP composites, glass fiber reinforcements control structural properties; whereas, resin type controls corrosion resistance and service temperature suitability.
Can structural properties differ in FRP materials with similar weight & appearance?
YES. Strength and stiffness of FRP composites are controlled by type, content, and alignment of its glass fiber reinforcements. To optimize structural properties, glass fibers must be in the right place, oriented in the right direction, and in the right amount.
Fig. A Chopped Strand: Inefficient load transfer
Approx. 25% reinforcing content (by wt.)
Fig. B Woven Roving: Weak at intersections
Approx. 40% reinforcing content (by wt.)
4. To optimize performance, reinforcement design requires a combination of unidirectional, non-woven continuous fibers oriented in longitudinal and transverse directions with a minimal amount of chopped fibers (Fig. C).
With this design, reinforcing fibers in fiberglass corrugated panels can efficiently make up 48 to 52% of the material weight. In structural (FRP) fiberglass beams, utilizing pultrusion process, glass fiber content can exceed 60% of the material weight.
Fig. C Unidirectional + Chopped: Optimum properties
Approx. 50% reinforcing content (by wt.)
What is the effect of reinforcement alignment for FRP Building Panels?
Strength and Stiffness are dependent on quantity of reinforcements. Amount of glass fiber reinforcing is dependent on the reinforcing alignment.
Continuous aligned fibers offer significantly higher glass content and structural properties than chopped strand or woven reinforcing. 50 times stronger than resin, glass fiber content and alignment controls strength and stiffness.
Fig. D
Deflection under load is dependent on quantity and alignment of reinforcements. The data shown in Fig. E indicates deflection for the continuous glass reinforced panel is 30% less than the woven panel and over than half less than the chopped strand pane.
Fig. E
Can corrosion resistance differ in new FRP materials with similar appearance?
YES. Type of resin is the primary control factor for corrosion resistance and temperature suitability. Polyester resins are predominantly used for construction applications due to cost and balance of properties including mechanical, chemical, and ease of processing. This discussion offers recommendations for isophthalic (iso-polyester), orthophthalic (ortho-polyester), and vinyl ester resins.
Can UV Protection differ in new FRP materials with similar appearance?
YES. For effective UV protection, UV stabilizers must be incorporated into the resin mix. UV stabilizers can be Ultraviolet Light Absorbers (UVA) or Hindered Amine Light Stabilizers (HALS), used individually or as blends. The additives are necessary to protect against UV breakdown or fiber blooming at the surface of fiberglass corrugated panels. In addition, a protective surface coating will provide extended color retention for opaque FRP materials and retention of light transmitting properties for translucent roofing panels and siding.
What requirements should be included in project specifications to help ensure higher quality FRP plus fair competition?
Product compliance will prevent excessive deflection that can lead to panel buffeting, fastener pullover, or damaged panels.
Please note: The recommended, minimum deflection limit of L/60 for FRP roofing and siding is the same as the requirement for metal panels as listed in ICC IBC-2021, 1604.3a. The allowable limits in the dated ASTM standard for Glass-Fiber-Reinforced Plastic Panels are not recommended due to the excessive deflection limits listed of L/20 for fiberglass siding and L/40 for fiberglass roofing panels. This ASTM criteria was developed over 30 years ago primarily by manufacturers of low performing, chopped strand, fiberglass panels. Most manufacturers, today, offer higher performing continuous glass reinforced panels, which are suitable for more conservative and appropriate deflection limits (L/60 min) that should be specified.
For additional information and assistance, please contact Enduro Composites, Inc. Our technical staff will be pleased to help with identifying appropriate materials and specifications for your project.