On the State of Technology Regarding the Use of Mechanical Fasteners in Composite Material Structures.

摘要

It is generally agreed that composite materials today offer many advantages over the use of metallic structures in many applicatons because of (1) their superior strength to density ratios and stiffness to density ratios which result in weight savings ranging from 20 percent to 40 percent in most aerospece applications, to 50 percent and more in some automotive applications, and (2) far fewer structural components are required. Nevertheless, structural components of composite materials must be joined together in some manner, and the joining introduces problems of a particular and unique nature. First of all polymer matrix composite materials are limited to adhesive bonding and mechanical fastening because welding of all kinds, brazing, soldering etc. are not possible. Secondly, almost all engineers agree that philosophically adhesive bonding is superior to mechanical fastening, primarily because fibers are not cut. But for those components that must be removable for any purpose, adhesive bonding must be substituted for by discrete mechanical fasteners, and the problems that arise are uniquely complicated. In this case fibers are cut, causing local weakening, complicated by the response of each ply with its particular orientation, the possibility of delamination, uncertainty of the failure criterion, etc. This report attempts to present the state of the technology in July 1978, to show what is known and understood, what needs to be studied, and what is required to design a bolted joint in composite materials. (Author)