Joint design: strength and fracture

Aspects of this subject are also dealt with in other articles, notably Acrylic adhesives. Durability - fundamentals. Joint design general. Joint design cylindrical joints. Joint design strength and fracture perspectives. In the article on Toughened acrylic adhesives, some properties are compared with those of Epoxide adhesives and anaerobic adhesives. 

Further consideration relating mechanics to joint design are given in Joint design strength and fracture perspectives, Durabiiity creep rupture. Durability subcritical debonding and Durability fatigue. 

For the best possible performance, joints should be specifically designed for adhesive bonding. In a few cases only can an adhesive be used on a joint not specifically designed for adhesives - mainly cylindrical joints. Bond stresses, materials, type of adhesive, surface preparation, methods of application and production requirements can then all be considered in relation to each other at the outset. The designer should consider especially the effect of shear, tension, cleavage and peel stresses upon the joint (Fig. 1) (see Joint design strength and fracture perspectives). 

Joint design strength and fracture perspectives D A DILLARD Two approaches to design of joints... 

The experimental work was performed to provide both material property Input to the design model and experimental verlflcatiori of model predictions. To this end small scale and scaled up joints were fabricated to determine their mechanical behavior. Experiments included measurements of elastic constants and of stress-strain curves as a function of temperature, tensile strength, shear strength, and fracture toughness. Some experiments were also performed on specimens fabricated entirely of the interlayer materials. 

Komatsu and others [64] found that the strength of double-lap joints was porpor-tional to the bond area for relatively short overlaps. However, for long overlaps, stress concentrations and fracture mechanics controlled the strength of the joint. The authors developed the following fracture-based design equation ... 

---