1485. Weight Control Program for a Graphite/Epoxy Aircraft

Paper

Abstract

Reduction of aircraft weight through use of graphite/epoxy composites is becoming increasingly attractive due to high fuel costs and increasing performance demands. The physical properties of composites render themselves incompatible with some of the techniques generally used for weight calculations and weight control
Weight is always an important area in an aircraft program, but since weight savings is the main reason for using composites, weight control, estimating, and reporting become items of greatly increased interest.
The basic challenge to be weight engineer of a composites program is to identify techniques that are incompatible with composite materials and to adjust or develop new techniques better suited to the material. This must be done while he carries on business as usual, plus many additional reports and studies that crop up due to the increased interest in weights.
Resin content can fluctuate considerably, thus affecting the accuracy of calculated weights. Integral design capability with this material saves both weight and money. However, because of its newness, this capability is sometimes overlooked. Blueprints take on quite a different look for laminates. Reliable structural weight estimation formulas are not readily available. Cost evaluation is a problem. General industry design standards have not been established. Different material thicknesses are available, and can save weight, but can be costly due to material qualification programs. These items require adjustment in approaches and techniques used by the weight engineers.
This paper identifies challenges that occur in a weight control program for a graphite/epoxy aircraft and outlines methods used at Lear Fan Limited to meet these challenges.