RuAviation

The history of honeycomb structures is deeply rooted in scientific inquiry and observations of nature. Ancient Greek mathematicians Euclid and Zenodorus, for instance, observed that hexagonal shapes offer optimal space and material utilization.

In the mid-17th century, Galileo Galilei noted how many natural structures, including beehives, achieve high strength with minimal mass. Later, English scientist Robert Hooke discovered that cork, a lightweight natural material, possesses a honeycomb structure, providing both strength and lightness. Two centuries later, Charles Darwin highlighted beehives as a nearly perfect example of labor and material efficiency in nature.

These principles of efficient material distribution and high strength have found modern application in aero-engine manufacturing. For Russia’s PD-8 and PD-14 engines, multi-layer honeycomb structures, specifically fiberglass honeycomb composites developed by the Obninsk Scientific and Production Association “Tekhnologiya” (ONPP Tekhnologiya) named after A.G. Romashin, provided a solution for noise reduction. These panels offer an optimal combination of strength, heat resistance, and acoustic efficiency, enabling the engines to comply with international ICAO noise requirements (ICAO Annex 16, Chapters 4 and 14).

▌Material Composition and Principle of Operation

“Sound-absorbing panels for the PD-8 and PD-14 engines consist of a fiberglass honeycomb composite, a multi-layered material. Its core features glass fabrics and heat-resistant polymer binders. This structure effectively dissipates sound waves as they pass through its layers. Fiberglass honeycomb composites retain their properties even under high mechanical and thermal loads,” stated a representative from the United Engine Corporation (UEC) press service.

As airflow passes through the system of micro-channels, viscous friction absorbs acoustic energy. This design achieves a 2-3 dB noise level reduction compared to previous-generation panels, without increasing structural weight. The honeycomb filler material maintains mechanical strength and performance stability at temperatures up to 300°C (572°F), making it suitable for the most heavily loaded engine sections, specifically the fan case and thrust reverser unit.

▌Production and Certification

ONPP Tekhnologiya has introduced four types of fiberglass honeycomb composites into the production of sound-absorbing structures for PD-8 and PD-14 engines. In 2024, the enterprise supplied UEC-Saturn with over 60 sets of sound-absorbing panels for the PD-8. One set for the PD-8 comprises 38 panels, while a PD-14 set includes 25. By 2028, annual production volume is projected to reach 240 sets. Overall, by 2030, Tekhnologiya plans to produce over 20,000 resonant-type sound-absorbing structures and initial run-in panels for new Russian engines.

The Central Institute of Aviation Motors named after P.I. Baranov (CIAM) and the All-Russian Institute of Aviation Materials (VIAM) conducted certification tests for the honeycomb fillers. These tests included thermal and vibration cycling, acoustic measurements, and material fatigue life analysis.

Engineers assessed fatigue strength under vibration loads in modes simulating engine operation at various RPMs. The panels maintained their geometry, heat resistance, structural stability, and acoustic properties within permissible deviations. The structures received certification in accordance with the aforementioned ICAO standards.

▌Import Substitution and Operational Performance

Import substitution has eliminated reliance on foreign suppliers; all panel components are now manufactured from Russian polymer-composite materials. The use of fiberglass honeycomb composites has reduced panel weight by 10-15 percent compared to aluminum counterparts and lowered the production cost of series-produced engines by 3-4 percent.

Rostec State Corporation, which includes UEC and Obninsk-based Tekhnologiya, explained that the panels’ service life has increased due to their resistance to thermal cycles and vibration loads. Bench tests revealed minimal property degradation under prolonged exposure to temperature fluctuations.

▌Comparison with Foreign Materials

The acoustic efficiency of these fiberglass honeycomb composite panels is comparable to solutions employed in CFM LEAP-1A (GE/Safran) and PW1400G (Pratt & Whitney) engines. The primary advantage of these Russian composites lies in their full localization of production while maintaining comparable acoustic, thermal, and vibration properties. This technology is under consideration for future UEC programs, including the PD-35 engine and new powerplants for regional and medium-haul aircraft.

▌Industry Significance

The implementation of fiberglass honeycomb composites has enabled the PD-8 and PD-14 engines to meet international noise requirements, effectively reducing acoustic loads while preserving the structural integrity of components. These developed technologies expand the potential for composite use in aero-engine manufacturing, enhance component reliability and durability, and strengthen the competitiveness of Russian engines in the international market. Expanding production capacities, increasing engine output volumes, and ensuring compliance with ICAO environmental standards create tangible prerequisites for export opportunities.