English

Abstract

Airframe applications of composite material structures have been investigated for a number of years. With the availability of advanced fibrous reinforcements of high specific strengths and moduli, airframe weight reductions of about 40 percent were frequently predicted. However, as actual development programs were completed it became apparent that weight savings from increased strength and stiffness could be easily offset by weight losses resulting from inefficient joining of these materials. Eliminating structural joints and cutouts (which are special joint cases if stressed covers are used) is impractical in present-day aircraft because of the requirements for manufacturing breaks, assembly and equipment access, and replacement of damaged structures. Optimum joint proportions have evolved from essentially invariant relationships between tension, shear, and bearing strengths (and moduli) of structural metals. Because of the fundamental differences in properties caused by the anisotropy and inhomogeneity of composites, design policies that were evolved for metal joints cannot be applied directly to composites. The basic strength and modulus relationships on which metal joint technology is based are variables in the composite structural design process. Thus, the design of optimum joints in reinforced composites must start in the selection and arrangement of the basic material constituents. The objective of this project is to create a 3D spacer fabric composite by simple hand layup technique and conduct mechanical tests on them by joining them in different methods. Thus, to find the joint that gives the highest strength. Also, to evaluate the failure modes of the specimens and predict the best joint configuration for the material under consideration. Three methods are followed for achieving viz. Mathematical method, Analytical Method and Experimental Method.