3333. The Development of Composite Landing Gear Components for Aerospace Applications

Paper

Abstract

Composites are being used increasingly for structural components for aircraft and space applications because of their superior specific strength and stiffness properties in comparison to aluminum and steel. The weight savings that were realized by applying composites used to be one of the main drivers to apply these materials. However, nowadays a reduction in fabrication cost is becoming important as well. The objective, therefore, is to combine new cost effective fabrication methods with lightweight structural concepts in order bring the exploitation of composite materials to a higher level.
Up to now, the autoclave process is the standard fabrication technique to produce composite components for the aerospace industry. Recent developments show the evolution of new cost efficient fabrication techniques and of composite materials for these new techniques. One of these (for the aerospace) new fabrication methods is Resin Transfer Moulding (RTM). The RTM fabrication concept is based on the injection of resin into a mould cavity containing dry fibers (preform). During the injection process, air in the mould is being replaced by resin and the fibers are impregnated. Although RTM tooling can be complex and expensive, RTM has several advantages compared to autoclave processing. One of these advantages is that thick complex shaped components can be made that would be very cumbersome or even impossible to make by autoclave processing. This means that designers now can design composite components as replacements for components made with metal forging.
In the framework of several technology programs the Structures Technology Department as part of the Aerospace Vehicles division of NLR developed several composite landing gear components for a large military helicopter and a fighter aircraft. These programs were carried out in close collaboration with the landing gear manufacturer, SP aerospace and vehicle systems. The targets of the programs were to achieve not only weight reductions of 20% but also to reduce the manufacturing costs by 15% and to achieve a reduction in lead-time.
Several different landing gear components were fabricated successfully by RTM and tested. All tested landing gear components failed beyond their required failure load levels. All program targets were met.
This paper will present an overview of the design concepts of these composite landing gear components. The RTM tooling concepts and the RTM manufacturing set-ups will be described and a brief overview of the test results will be given.
Based on the results achieved, composite landing gear components are now considered to be feasible for application in next generation civil and military aircraft.