Tempered glass, heat-treated to enhance strength and safety, is a reliable material in aviation for its durability and controlled breakage properties.

Background and Evolution

Tempered glass was developed in the early 20th century, with its toughening process refined by the 1930s for automotive and industrial use. Its aviation adoption began in the 1940s, appearing in aircraft like the Lockheed Constellation for interior fittings and gauges. By the jet age, it supported designs like the Boeing 727, evolving with stricter safety standards into modern aircraft such as the Airbus A320.

How Tempered Glass is Used

• Interior Partitions: Forms cabin dividers and decorative panels, resisting breakage and noise.
• Galley Equipment: Used in oven doors and serving trays, enduring thermal stress and impacts.
• Instrument Covers: Protects analog gauges and minor displays, maintaining clarity under vibration.
• Lighting Fixtures: Shields cabin and secondary exterior lights, handling heat and minor impacts.

Why Tempered Glass is Used

• Increased Strength: Thermal tempering boosts tensile strength to ~120–200 MPa, 4–5 times stronger than annealed glass.
• Safety Breakage: Shatters into small, blunt granules rather than sharp shards, reducing injury risk.

• Thermal Resistance: Tolerates temperature differences up to 250°C, suitable for galley and lighting uses.
• Cost-Effectiveness: Cheaper to produce than laminated or chemically strengthened glass, balancing performance and budget.
• Durability: Resists scratches and wear (6 Mohs), adequate for non-critical applications.

Technical Specifications

• Density: ~2.5 g/cm³, standard for soda-lime glass.
• Thickness: Typically 3–6 mm for aviation uses.
• Composition: Primarily soda-lime (70% SiO₂, 15% Na₂O, 10% CaO).
• Surface Stress: ~10,000–20,000 psi from tempering process.

Comparison to Alternative Materials

• Laminated Glass: Safer with interlayers but heavier and costlier, preferred for windshields.
• Chemically Strengthened Glass: Stronger and scratch-resistant, but more expensive and less thermally adept.
• Borosilicate Glass: Better heat resistance (~500°C), though less impact-strong.
• Acrylic: Lighter and shatter-resistant, but softer and heat-sensitive.

Tempered glass offers a practical mix of strength and affordability.

Role in Modern Aviation

In aircraft like the Boeing 737 and Airbus A320, tempered glass supports interior fittings, galley components, and minor instrument covers. It plays a secondary role to laminated glass in critical areas and chemically strengthened glass in displays, as seen in the Boeing 787 Dreamliner.

Environmental and Economic Considerations

• Production: Energy-intensive heat treatment raises costs slightly, offset by scalability and recyclability.
• Cost: Lower than advanced glasses, ideal for mass production.
• Recycling: Fully recyclable into new glass, supporting sustainability.

Future Trends

Thinner tempering processes or hybrid coatings could enhance its use in lightweight interiors. However, composites and advanced glasses may limit its growth in high-stress or high-tech applications.

Summary

Tempered glass’s strength, safe breakage, and affordability make it a staple for aviation’s interior and minor components. Since the 1940s, it has provided reliable durability, complementing more specialized materials in modern designs.