Designer Solid Shims for Assembly of Advanced Carbon Composite Pre-preg based Aircraft Structures

Abstract

A modern combat aircraft uses considerable amount of advanced composite material in structure build for better flight performance, stealth requirement and higher payload. Combat aircrafts made using composite structure require large numbers of custom shims of various thickness and shapes throughout interface surface, which are presently prepared by suit on assembly process to fill gaps measured between sub-structure parts and skin. The scope of study is four plus generation combat aircraft like Indian Light combat aircraft. These gaps arise due to composite raw material characteristics, mould tool and manufacturing process which results in geometry variation. This research has focussed the delta wing integral fuel tank composite structure. However, these research findings can be applied in other wing shapes made by composite part within the scope. The shims, whether liquid or solid, are necessary to eliminate gaps, maintain structural performance and minimize pull-down forces required to bring the aircraft into engineering nominal configuration for aerodynamic efficiency. Customized shims amount to significant delays in production with much of the time being spent in the critical path of the aircraft assembly. In this research work, we present an alternative strategy for the use of designer solid shim, based on redesign of lay-up moulding tool (female type) and shims manufacturing with change in existing manufacturing value stream. The experimented method has reduced the manufacturing cost of wing assembly, shorten the shimming process cycle and improve the assembly efficiency, product quality and performance.