Enhancing composite interior part manufacture

From floor panels to overhead bins, from seats to lavatories to inflight entertainment, aircraft interior parts form the foundation of high quality passenger experiences. Modern aircraft cabins comprise thousands of interior parts, made from thousands of pounds of advanced composite materials including honeycomb cores, thermoset prepregs and more. Designing composite interior parts means balancing FST (Fire, Smoke and Toxicity) requirements with low weight and high durability, all while optimizing production efficiency and maintaining commercial viability.

Effective void filling is key to striking this balance. Many composite interior parts, such as honeycomb core sandwich panels in floors, ceilings, walls, lavatories and cargo hold liners, have complex, contoured forms. This results in voids, gaps and edges in need of filling or sealing. Unfortunately, many common void filling compounds feature suboptimal shop handling properties – hand measuring and mixing, short work times, freezer storage and more – that cause excess product waste while driving up production costs and cycle times.

Aircraft manufacturers and tier suppliers have collaborated with aviation and materials science experts at 3M to solve void filling challenges and dramatically enhance production efficiency. Engineers at Diehl Aviation, an international first tier supplier of avionics and cabin integration, have cited important preparation and shop handling problems presented by existing fillers. Short work life and hand mixing requirements limit preparation to roughly 1 kg of compound at a time, while freezer storage requirements mean that precise quantities of each component must be measured and thawed 24 hours before mixing.

Diehl identified 3M™ Scotch-Weld™ Structural Void Filling Compound 3550 B/A FST as the optimal solution to reduce prep time and accelerate the void filling process. Scotch-Weld 3550 B/A FST is a low-density epoxy compound suitable for honeycomb core sandwich constructions and other composite interior parts. It is extrudable and pumpable with excellent flow and non-sag properties and a work life of up to 120 minutes.

Like Diehl, engineers at Embraer selected Scotch-Weld 3550 B/A FST for its automated mixing capabilities and enhanced pumpability over existing fillers. However, several issues were identified during visual inspection and weight/volume inspection:  

• Incomplete curing
• Density increases of up to 55%
• Nonlinear flow rates

Further testing at the 3M Aerospace Lab traced the issues back to a pumping and dosing system that:

• Compressed filler components, producing incorrect ratios of base and catalyst that inhibited curing
• Damaged the hollow glass microspheres used to reduce filler density
• Applied excess shear force, causing unexpected changes in viscosity

Working bench to bench with 3M enabled Embraer to identify a pumping and dosing system to solve these issues and meet their precise void filling needs.

Ensure products meet all applicable specifications, standards, and maintenance manual requirements for the platform being worked on and validate all aircraft approvals against current technical documentation.

Diehl Aviation is a division of Diehl Stiftung & Co. KG and combines all aviation activities of Diehl Group under one roof. In the aviation industry, Diehl Aviation - including Diehl Aerospace (a joint venture with Thales) - is a leading system supplier of aircraft system and cabin solutions. Diehl Aviation currently has more than 4,000 employees. Its clients include leading aircraft manufacturers Airbus, Boeing, Bombardier, Embraer, military partners, manufacturers of eVTOL aircraft as well as airlines and operators of commercial and business aircraft worldwide.

A global aerospace company headquartered in Brazil, Embraer has businesses in Commercial and Executive aviation, Defense & Security and Agricultural Aviation. The company designs, develops, manufactures, markets aircraft and systems, providing Services & Support to customers after-sales.

Since it was founded in 1969, Embraer has delivered more than 8,000 aircraft. On average, about every 10 seconds an aircraft manufactured by Embraer takes off somewhere in the world, transporting over 145 million passengers a year.

Embraer is the leading manufacturer of commercial jets up to 150 seats and the main exporter of high value-added goods in Brazil. The company maintains industrial units, offices, service and parts distribution centers, among other activities, across the Americas, Africa, Asia and Europe.

Contact a 3M Aerospace expert