Joining mechanisms Fasteners, mechanical

Fastener connection—A mechanical joint held together by fasteners that are additional to the components being joined. The fastener may be used directly in the transfer of load between the components to be joined (e.g. as in a bolted, riveted or screwed connection) or indirectly (e.g. as in a friction gripped, clamped or strapped connection). 

Hart-Smith, L.J., Joining of Composites, Douglas Paper 7820, published as Joints. In C.A. Dostal (Ed.), Engineered Materials Handbook, Vol. I, Composites, ASM International, Metals Park, OH. November 1987, pp. 479-495. AKso published as Joining, mechanical fastening. In S.M. Lee (Ed.), International Encyclopedia of Composites, Vol. 2. VCH, New York, 1990, pp. 438-460. Second revised edition published in 2001. 

Polymers are characteri2ed as thermosetting and thermoplastic with respect to the methods by which they are joined. Thermosetting polymers are permanently hard and do not soften upon the apphcation of heat they are joined by mechanical fasteners and adhesives. Several methods have been devised to join thermoplastic polymers, as weU as thermoplastic composite materials, which soften upon heating. 

Simply bonding a stiffener to a panel with adhesive is certainly a very feasible and natural procedure with typical composite structure construction. We have not discussed any procedure for joining parts except co-curing. Alternatively, to use film adhesive for bonding parts together, we simply cut a sheet or film of adhesive to the proper size, place it between the two parts that we wish to bond together, and then go through a cure cycle that causes the adhesive to adhere to both the stiffener and to the panel itself. We can also mechanically fasten any stiffener we like to a panel. 

A variety of techniques is available for joining plastics to themselves or to other materials—mechanical fastening, welding, and bonding with adhesives—and all are used extensively. Each method has both advantages and drawbacks for plastics, bonding might be said to be preferable when they are to be joined with dissimilar materials. 

Sometimes conventional welding or a mechanical joining process is just not possible. Substrate materials may be incompatible for metallurgical welding due to their thermal expansion coefficients, chemistry, or heat resistance. The end product may not be able to accept the bulk or shape required by mechanical fasteners. 

In the electrical and electronic equipment market, adhesives compete with other joining methods such as mechanical fasteners, brazing, welding, soldering, and thermocompression bonding. Major uses of adhesives in the electrical and electronic equipment market are shown in Table 1.5. Adhesives are generally the preferred method of joining whenever... 

Mechanical Fastening, Joining, and Assembly, James A. Speck... 

Joining refers to mechanical methods of fastening parts to each other. Joining techniques usually do not require adhesives and can be accomplished by designs similar to those applied to attach metals. This topic is covered in great detail in Ref. 27. 

Interference Fit - A mechanical fastening method used to join two parts, such as a hub and a shaft, in which the external diameter of the shaft is larger than the internal diameter of the hub. This interference produces high stress in the material and must be determined carefully to avoid exceeding the allowable stress for the material. Stress relaxation can occur in interference fits, causing the joint to loosen overtime. Also called press fit. 

U.S. annual welding expenditures, because mechanical fastening is the joining method of choice. However, the bulk of FSW development dollars has been spent by these sectors. As a result, the broader automotive, marine, heavy manufacturing, light manufacturing, and construction markets for FSW implementation have been neglected. 

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