What Are Structural Adhesives and How Are They Used in Aerospace Manufacturing

Rivets, bolts, and other mechanical fasteners have long served as the primary means for helping aircraft assemblies and structures withstand great stress during flight. However, engineers are increasingly relying on structural adhesives, these high-strength bonding materials being designed to hold components together permanently and uniformly distribute stress in a more lightweight manner. This blog will cover how adhesives are strategically applied in aerospace manufacturing, as well as dive into some of the most common types employed.

The Use of Structural Adhesives

Capable of joining metals, composites, and hybrid structures alike, structural adhesives are used extensively in the following areas:

• Wing-to-Body Joints: In conjunction with mechanical fasteners, adhesives often join composite wing covers and center box sections to the fuselage structure. These bonded joints are useful for providing continuous load transfer over larger surface areas, improving fatigue performance and stiffness.
• Honeycomb Sandwich Panels: Structural film adhesives are critical for bonding thin face sheets to the honeycomb cores found in components like floor panels, wing flaps, ailerons, and door assemblies, presenting high stiffness-to-weight ratios that allow panels to remain rigid under aerodynamic and pressurization loads.
• Composite Fuselage Sections: Structural adhesives are sometimes used to bond large composite fuselage panels and skin sections to stringers and frames in order to lessen overall rivet count, part weight, and potential stress concentrations. The result is a smoother aerodynamic surface and improved structural efficiency across the fuselage barrel.
• Interior Assemblies: Lightweight structural and semi-structural adhesives are widely employed in the installation of interior assemblies, including floor panels, insulation linings, fairings, and sidewall panels. In addition to simplifying installation, they contribute to noise and vibration reduction by providing continuous, flexible bonding lines that dampen mechanical transmission.

In addition to all the aforementioned advantages, structural adhesives also facilitate the broader use of advanced lightweight materials like carbon fiber-reinforced polymers (CFRP) and titanium, which can be difficult to join with conventional mechanical fasteners. These materials can be sensitive to localized drilling or mechanical deformation, so adhesive bonding provides an effective alternative that minimizes stress concentrations. 

Common Types of Aerospace Structural Adhesives 

A few different types of structural adhesives are available to suit different operating environments and materials, with the most widely utilized formulations including:

• Epoxy Adhesives: Epoxy formulations are characterized by high shear and tensile strength, strong chemical resistance, and reliable adhesion to metals and advanced composites. Certain aerospace-grade epoxies retain mechanical properties at elevated temperatures and under cyclic loading, so they are often the main choice for primary structural bonds.
• Acrylic Adhesives: Acrylic adhesives are valued for their rapid curing times and strong impact resistance across a moderate temperature range, their versatility and ease of application making them well suited for high-throughput production environments. As a result, they are often employed in the assembly of interior components, access panels, and secondary structures.
• Urethane Adhesives: Urethane adhesives provide excellent flexibility, their elasticity helping to prevent cracking or delamination in areas subject to dynamic loads, vibration, or thermal expansion differences. These characteristics make them particularly effective for bonding dissimilar materials, such as composites to metals. 

Beyond formulation, structural adhesives can come in different consistencies, including film, paste, and liquid forms. Film adhesives are typically pre-cast sheets that provide uniform bond-line thickness and consistent mechanical properties across large surface areas. On the other hand, paste adhesives resist flow under static conditions but spread easily under pressure, which is ideal for filling gaps or bonding localized joints with a controlled application and minimal sagging. Meanwhile, liquid adhesives, by contrast, are lower in viscosity for use in smaller connections.

Gain Dependable Access to Quality Adhesives with ASAP Semiconductor

In summary, though they do not entirely replace fasteners, adhesive materials present exceptional benefits in bonding performance and design flexibility for aircraft and spacecraft structures. If you are interested in finding adhesive kits that are made for aircraft use, turn to ASAP Semiconductor. Through this comprehensive distribution platform, customers can peruse countless options for aviation materials that are sourced exclusively from reputable manufacturers who adhere to the highest quality and compliance standards. With additional commitments to competitive and curated fulfillment options, get in touch with our team to see how ASAP Semiconductor can serve as your go-to procurement partner.