Why use FTI products in composites?
FTI product systems provide simple installations, design flexibility, and improved performance. They eliminate the risk and time associated with sealants, satellite holes, and other types of interference fit products. Each product is radially expanded from an initial clearance fit to lock it into the structure and provide uniform contact with the hole surface resulting in the following advantages over other assembly methods:
• Improved open hole compression strength.
• Faster product installation and joint assembly.
• Hole protection in areas where bare holes can wear or wallow.
• Reduced arcing and laminate damage caused by lightning strike.
• Improved electrical conductivity through fastened joints to grounding locations.
• Simplified repair.
• Better open-hole fatigue life.
• Higher installation reliability and repeatability.
FTI expanded products achieve excellent bonding and grounding or earthing performance because each product is radially expanded from a clearance fit starting hole to produce a final interference fit in the structure or component. Our highly repeatable process produces uniform contact with the hole surface without gaps or insulating sealant.
GromEx panel liners are used to protect composite panels from lightning strike damage and hole wear. They are suitable for use with any class of fit fastener and can be used to facilitate the installation of net fit fasteners in load transfer applications. GromEx is available in common fastener configurations including “T-shape and 100° countersunk configurations.
GromEx Panel Inserts Improve Lightning Strike Performance Over Glued-In or Swaged-In Grommets/Liners
See our GromEx product page for more information.
FTI’s proven ForceMate bushing installation process works well in composites providing a fast, consistent installation with superior performance to bonded and shrink fit bushings. The process uses a standard FTI puller unit with a different mandrel and nose cap, which are optimized for the unique properties of composite laminates.
Composite to Metal Fastening
The ForceMate bushing installation system facilitates one-up assembly of metal/composite hybrid structures, thereby reducing cycle times and labor costs.
• Installs bushings in the metal and composite at the same time with tailored relative expansion levels.
• Improves the fatigue life of the metal structure.
• Enables structures to be line-reamed without disassembly.
• Eliminates the need to de-burr titanium structure during assembly.
• Provides for simple rework if hole is drilled oversize or off position.
• Supports alignment tolerance.
• Accommodates thermal mis-match of materials.
See our product page on ForceMate for more information.
ForceTec rivetless nut plates for use in composites are available in stainless steel and titanium in a variety of sizes and configurations including open style, domed, high float, and panel fastener configurations. The nut plates are dry film lubed for a mandrel only installation using a standard FTI puller unit with a mandrel, nose cap, and chuck assembly optimized for the special characteristics of composites.
Although FTI’s installation system for ForceTec in composites uses a much lower expansion level than metals, the resulting torque out values are comparable, as the sample data below indicate. ForceTec is suitable for use in grip lengths as low as 0.06 inch (1.52 mm).
ForceTec retainers can be used to compensate for tolerance stackup in structural assembly and provide the hole filling strength advantages of a net or interference fit fastener without the access constraints or bolt removal challenges. The test data below are examples of how ForceTec performs in static compression and fatigue versus both open and filled holes.
ForceTec Product Specification
FTI has recently released a product specification for our ForceTec Rivetless Nut Plate in Composite. You may register or login to your account to download this specification. Go to Login page >>
See our product page on ForceTec for more information.
FTI manufactures expanded nut systems for almost any application including honeycomb core panels and blind nut installations. Please call us for guidance with your design.
FTI spent many years researching and developing installation process parameters for its expanded products in a variety of composites to ensure a safe, highly-repeatable process. Bushings and nut plate retainers were installed in a large number of materials and thicknesses to study the effect of applied expansion on laminate integrity.
To ensure that expanded product installation process parameters for composites meet current acceptable manufacturing standards, FTI performed extensive laminate characterization studies using standard NDI methods and micrographs. All FTI expanded product installations at the recommended process parameters showed no indications of damage when evaluated with standard NDI methods such as automated pulse-echo ultrasonic, automatic through-transmission ultrasonic, x-ray, and manual pulse-echo ultrasonic.
FTI also sectioned and microscopically examined the installed products and discovered some isolated microcracks in some holes (see photomicrographs below). However, the cracks did not extend around the hole and the surface ply cracks were much smaller than the drilling allowable. FTI found no detrimental impact during static and fatigue testing.
Mechanical testing was performed to determine the effect of increasing the diameter of a hole and installing an expanded product. Testing showed that expanded products increased the open hole fatigue strength and open hole compression strength. Tension and bearing results were commensurate with the larger hole diameter and reduced net section.