5.1 Adhesive Joint Design

5.1.1 Assemblies and Joint Stress Distribution

Alternative joining techniques, such as welding or riveting, have specific benefits in certain situations, such as extreme temperatures and harsh chemical environments, where adhesives may not be suitable. However, in nearly all other circumstances, adhesives can provide an exceptionally robust and reliable solution if the assembly is designed correctly. Adhesive assemblies excel with the uniform distribution of stress, and a well-designed assembly will often be stronger than many alternative joining methods such as riveting or bolting.

As shown in Figure 104, the stress distribution of adhesive bond lines is significantly more uniform than bolting or even welding. The even stress distribution exhibited by a correctly designed bond line has several advantages. It will primarily help prevent substrate fatigue and create a stronger, more impact-resistant assembly.

Figure 104 Different types of joints and their stress distributions. Referring to the previous classification, periodic is bolting, welding is linear and adhesives is area

Adhesives can be used successfully in a wide range of processes and can be integrated into nearly any manufacturing environment. As shown in Table 16, adhesives can offer various benefits that many alternative joining methods do not, such as invisible application or increased aesthetics, better stress distribution, uniform strength across the assembly, no surface/substrate damage, no corrosion and decreased parts inventory. While commonly used to bond similar substrates, adhesives are often the only choice for bonding dissimilar substrates.

Table 16 Comparison of traditional joining methods vs using adhesives technologies

CONTAINMENT	ADHESIVES	BLIND RIVET	WELDING	SCREW	NUT, BOLT & WASHER	TUBULAR AND SEMI-TUBULAR RIVET	SOLID RIVET
Invisible in application
Stress distribution
High tensile & shear strength
Different materials
Can join different materials
High and low temperature resisitance
No hole required
Vibration resistant
Uniform strength
All work done from one side
Eliminates heat distortion
Clean appearance/aesthetics
Fastens in one operation
Joins without bulky equipment
Pressure-tight (without seal)
Tools readily available
Can be installed without power
Small capital investment
Minimum equipment needed
Tamper resistant
Holds plastic
Easy alignment of work surfaces
Prevents surface damage
Minimum back-up space
Flush finish
Wide grip range
Low parts inventory
Eliminates equipment adjustment
Requires minimal set-up time