Applications of Structural Blind Fasteners in Automotive

Applications of Structural Blind Fasteners in Automotive

A practical engineering guide to enabling multi-material vehicles, safer EV battery systems, and maintenance-free structural joints

Introduction: Why Fasteners Suddenly Matter More Than Ever

For decades, fastening was a background topic in automotive engineering. If something had to be joined, you welded it, bolted it, or popped a rivet and moved on. That logic no longer works.

Modern vehicles are no longer made of one metal. They are multi-material structures—aluminum extrusions bolted to ultra-high-strength steel, carbon-fiber composites bonded to magnesium castings, and battery enclosures that must remain watertight for a decade.

This is where structural blind fasteners (SBFs) have become one of the most critical technologies in automotive manufacturing.

Unlike ordinary pop rivets, these are not alignment aids. They are load-bearing structural components used in chassis rails, crash zones, EV battery trays, and even OEM-approved collision repairs.

What Makes a Fastener “Structural”?

A non-structural rivet behaves like a hollow straw squeezed between two sheets. It holds position but collapses under real load.

A structural blind fastener is engineered so that the mandrel is permanently locked inside the shear plane after installation. This retained mandrel becomes a secondary load path that dramatically increases both shear and tensile capacity compared to standard blind rivets. Industry sources confirm that mandrel retention systems deliver the highest shear and tensile strength values available among blind fastener designs.

The Mechanics of Mandrel Retention

Why Structural Fasteners Outperform Pop Rivets

During installation, a pneudraulic or battery tool pulls the mandrel until:

• The blind side expands fully behind the joint stack

• A locking collar mechanically swages into place

• The mandrel fractures above the locking groove and remains inside the rivet body

This creates a solid, 360-degree mechanical lock through the joint thickness. The mandrel effectively becomes an internal steel core, dramatically improving:

• Shear load transfer

• Pull-through resistance in thin aluminum sheets

• Fatigue life under transverse vibration

• Resistance to self-loosening under repeated cyclic loading

The mandrel retention design delivers among the highest shear and tensile values available in the blind fastener industry, with no re-torquing requirements over the fastener’s service life.

Joining the Future: Enabling Multi-Material Architectures

Resistance spot welding works when you join steel to steel. It fails when you try to weld:

• Aluminum to UHSS (ultra-high-strength steel)

• Aluminum to magnesium

• Composites to metals

Why? Because heat destroys the microstructure and forms brittle intermetallic compounds at the interface. Metallurgical research confirms that when aluminum is fused with steel, compounds such as Fe₂Al₅ and FeAl₃ form in the heat-affected zone, severely reducing ductility and mechanical properties.

Structural blind fasteners solve this through cold-joining. No melting. No metallurgical damage.

Rivet-Bonding: The Hybrid Advantage

The real breakthrough is rivet-bonding, a hybrid joining process where:

• Structural adhesive is applied between the materials

• The blind fastener clamps the joint and acts as a “cleco” while the adhesive cures

• The cured adhesive forms a dielectric barrier that electrically isolates aluminum from steel

This prevents galvanic corrosion, distributes peel loads over a wider area, and increases joint stiffness compared to rivets alone. The combination of mechanical clamping and adhesive bonding creates joints that resist both shear and peel loading—a performance advantage unavailable with rivets or adhesive alone.

Rivet-bonding has been successfully implemented in automotive applications including aluminum body repairs and multi-material assemblies, with proven field performance in premium vehicle platforms.

Safety-Critical EV Applications

Battery Enclosures, Sealing, and Thermal Systems

In EVs, the battery pack is the structural heart of the vehicle. Any moisture ingress can cause catastrophic short circuits.

Closed-end structural blind fasteners are engineered to seal during setting, enabling OEMs to achieve fluid-tight joints meeting international waterproof standards. Typical applications include:

Structural Blind Fasteners vs Welding

Performance, Safety, and Cost Comparison

• Re-torquing schedules

• NVH warranty claims

• Thermal distortion rework

• Post-weld inspection steps

OEM Strategic Implementation

Ford F-150 & Tesla Model 3

Both Ford and Tesla utilize structural blind rivets in their aluminum repair procedures.

The Ford F-150 includes structural blind rivets in approved body-in-white repair procedures to restore original structural performance in damaged areas. Service documentation specifies blind rivet applications for floor pan, cowl, and body repair scenarios where OEM performance standards must be maintained.

Tesla Model 3 service documentation specifies fastening procedures for battery tray and floorpan repairs, with careful attention to heat input management. Welding procedures in these areas are restricted due to battery safety requirements and thermal considerations that could compromise battery pack integrity. The combination of fastening and adhesive bonding preserves the designed thermal and structural properties of the battery enclosure.

Collision centers and service facilities that follow OEM repair procedures maintain certification standards and preserve vehicle crashworthiness after repairs.

Tooling & Installation Systems

Visual inspection rule:
If the mandrel head is not seated flush inside the rivet body, the joint is rejected.

Failure modes to monitor:

• Substrate tear-out

• Mandrel head shear

• Grip mismatch

Heavy-Duty Commercial Applications

Truck chassis, suspension mounts, trailer frames—these live in vibration hell.

Threaded bolts loosen. Structural blind fasteners do not.

They create joints that remain rigid after hundreds of thousands of kilometers without squeak-and-rattle or retightening—a game-changer for fleet uptime. Unlike threaded fasteners requiring periodic maintenance and re-torquing, structural blind fasteners maintain their clamping force indefinitely due to the mechanical lock created by mandrel retention.

Smart Fasteners & IoT

Predictive Maintenance Becomes Reality

The next evolution is sensor-embedded structural fasteners that transmit:

• Load

• Vibration

• Temperature

These feed vehicle ECUs and factory MES platforms, enabling real-time structural health monitoring—a foundational capability for autonomous fleets and smart factories.

FAQs

Q1: Why are SBFs better than welding for multi-material vehicle (MMV) platforms?
A: They avoid heat-induced microstructural damage and intermetallic compound formation at dissimilar material interfaces. Cold-joining preserves the mechanical properties of lightweight alloys.

Q2: How do closed-end designs achieve waterproof sealing?
A: Closed-end structural blind fasteners plastically deform during setting to form a fluid-tight barrier, enabling sealed joints without supplemental sealants.

Q3: Are they required for aluminum collision repair?
A: Yes—OEM manuals specify fastening procedures to restore crashworthiness and maintain vehicle safety integrity after damage repair.

Q4: What advantages do they provide over threaded bolts?
A: Mandrel retention eliminates self-loosening from vibration, eliminates re-torquing schedules, and provides superior performance under transverse and fatigue loading conditions.

Conclusion

Structural blind fasteners are not just hardware. They are the silent enablers of:

• EV safety

• Multi-material architectures

• Maintenance-free fleets

• Smart factory ecosystems

They are the reason modern vehicles can be lighter, safer, and more durable—without a single weld bead in sight.