Integral Micro-Mechanical Interlock (IMMI) Joints for Polymer-Matrix Composite Structures

Abstract

A relatively new concept for producing joints in structures made from polymers with potential for polymer-matrix composites is presented, described, positioned, and organized. Named here integral micro-mechanical interlocking or IMMI (pronounced "eye-my") joints, the concept is derived from several different traditional integral attachment approaches, but on a finer scale. As such, IMMIs offer the freedom from fasteners and fastening tools and the ease of assembly sought in design for assembly (DFA) philosophy, with expected improvements in strength compared to joints in polymer-matrix composites made by conventional mechanical fastening or adhesive bonding. The position of IMMIs within an overall hierarchy ofjoining methods is shown, and three fundamental approaches are identified, described, and illustrated, depending on whether the interlock is accomplished in a rigid, elastic, or plastic fashion. An IMMI design matrix is also presented that shows general performance expectations in shear, tension, and overall load-carrying capability and utility. The overall intent of the paper is education, organization, and stimulation of thinking.