Composite Blind Rivets for FRP & Composite Panels

For fiberglass or FRP panels, large flange blind rivets or expansion-type structural blind rivets are the best choice. These rivets provide a larger bearing surface after installation, distributing loads more evenly across the composite surface and thereby reducing localised stress concentrations. As FRP is a laminated composite material with relatively low tensile strength, using rivets with smaller flanges may lead to material tearing or localised damage. The larger flange or bulbous structure effectively mitigates this risk while reducing interlaminar shear stresses within the composite, thereby lowering the likelihood of delamination.

In engineering practice, it is recommended that the diameter of the rivet flange be at least 1.5–2 times the diameter of the rivet shank. This further enhances connection stability and reduces the risk of damage to the FRP material.

If rivets are incorrectly selected or installed, blind rivets may indeed cause cracking or damage to composite materials.

For instance, if the rivet flange is too small, resulting in insufficient load-bearing area, localised stress concentration may occur on the FRP surface; excessive tension during installation may also cause compression damage to the laminate structure. Furthermore, overly tight drill hole dimensions, rough hole walls, or inherently thin composite material thicknesses may all increase the risk of material cracking.

To mitigate these issues, engineering practice typically employs large flange rivets or composite rivets specifically designed for composite materials, which provide a larger bearing surface area. Concurrently, the installation load must be controlled during fitting to avoid excessive clamping forces, while ensuring drill edges are smooth and hole dimensions are appropriate. Provided these fundamental principles are followed in selection and installation, blind rivets represent a stable and reliable solution for joining composite structures.

In the joint structures of FRP (fibre-reinforced polymer) panels, delamination is a relatively common form of damage. It is typically caused by excessive localised loading or stress concentration.

To mitigate this risk, several straightforward yet effective engineering measures are commonly employed. Firstly, the use of wide-flange rivets can create a larger bearing surface at the blind end, distributing loads more evenly and thereby reducing localised stress on the composite laminate. For thinner FRP panels, many engineers also incorporate backing washers or backing plates on the reverse side to minimise the risk of material tearing or delamination.

Furthermore, careful control of installation load during fitting is essential to prevent excessive clamping forces from causing compression damage to the composite material. Drill hole dimensions are also critical; it is recommended that the hole diameter be approximately 0.1–0.2 mm larger than the rivet diameter. This ensures smooth installation while minimising stress concentration within the material.

Rivets are more suitable for thin-walled structures, such as composite panels or lightweight structural components, as riveting can reduce localised stress concentrations in the material while maintaining connection strength. Furthermore, riveted joints resist loosening, offering excellent stability in vibratory environments. In contrast, bolts are better suited for structural connections subjected to higher loads, particularly where greater clamping force or a detachable connection is required.

Moreover, blind rivets offer distinct advantages through their capability for single-sided installation (blind installation). Within enclosed structures or assembly environments accessible only from one side—such as composite boxes or internal connections within sandwich structures—blind rivets significantly enhance installation efficiency and simplify the assembly process.

In marine environments, it is recommended to use stainless steel rivets or sealed rivets within composite structures. This is due to the high salinity of marine environments, which presents a significant risk of corrosion.

Should conventional aluminium rivets be employed, galvanic corrosion may occur between them and other metallic materials, thereby compromising the structure’s long-term reliability.

In engineering practice, common choices include A2 or A4 stainless steel rivets, alongside sealed stainless blind rivets, to enhance the stability and durability of marine composite structures during prolonged service.

When installing rivets in composite materials (such as FRP, GFRP or carbon fibre laminates), hole diameter control is critical. Compared to metallic materials, composites are more sensitive to localised stresses. It is recommended that the hole diameter equals the rivet diameter plus 0.1–0.2 mm.

It is recommended to use in conjunction with large flange blind rivets or peel rivets to increase the load-bearing surface area and provide further protection for the composite structure.

If the appropriate rivet type is selected, additional washers are unnecessary. Structures like large flange blind rivets or bulb tite rivets inherently provide a larger bearing surface, distributing loads more evenly across the composite surface. Therefore, in most composite panel applications, using the correct rivet type typically achieves a stable and reliable connection without requiring additional washers.