Overview
Conventional racks for avionics were made from metal. Most of the avionics fielded today offer a monolithic architecture in form of a closed box packed with electronics and lots of connectors at the front or the back with corresponding heavy cable harness. More recent developments go for modular avionics, packing electronics with standard dimensions and connectors that assure physical interchangeability.
The proper housing protects the electronics against the environment, ensures EMC and supports the thermal management. In order to reach higher power density and lower costs the optimisation of the housing is a must.
The amount of electronically controlled tasks in modern aircraft is increasing steadily and also the contribution of racks for avionics to the overall weight of an aircraft has reached a magnitude that requires an analysis to obtain mass reduction.
Modern structures built in composite technology are able to provide important mass savings with respect to conventional designs. The advantages of high-performance composites are many, including lighter weight, the ability to tailor lay-ups for optimum strength and stiffness, improved fatigue life, corrosion resistance and, with good design practice, reduced assembly costs due to fewer detail parts and fasteners.
Composite enclosures can be made significantly lighter than machined aluminium enclosures and may be produced at an affordable cost provided a modular approach is followed while possessing equal or better mechanical and thermal performance.
The objective of the present work was the development of a lightweight “open box” ARINC housing (ARINC standards) which withstands vibration levels C/C1 according to RTCO-DO160.
A lightweight and modular composite solution was proposed. Using advanced fibre-reinforced composite materials, a 40 % of weight reduction in the housing was estimated.
Funding
Results
Executive Summary:
Conventional racks for avionics are made from metal. Most of the avionics fielded today offer a monolithic architecture in form of a closed box packed with electronics and lots of connectors at the front or the back with corresponding heavy cable harness. More recent developments go for modular avionics, packing electronics with standard dimensions and connectors that assure physical interchangeability.
The amount of electronically controlled tasks in modern aircraft is increasing steadily and also the contribution of racks for avionics to the overall weight of an aircraft has reached a magnitude that requires an analysis to obtain mass reduction.
The proper housing protects the electronics against the environment, ensures EMC and supports the thermal management. In order to reach higher power density and lower costs, the optimisation of the housing is a must.
Modern structures built in composite technology are able to provide important mass savings with respect to conventional designs. The advantages of high performance composites are many, including lighter weight, the ability to tailor lay-ups for optimum strength and stiffness, improved fatigue life, corrosion resistance and, with good design practice, reduced assembly costs due to fewer detail parts and fasteners.
Composite enclosures can be made significantly lighter than machined aluminium enclosures and may be produced at an affordable cost provided a modular approach is followed while possessing equal or better mechanical and thermal performance.
The objective of the present work is the development of a composite “open box” ARINC housing (ARINC standards) which withstands vibration levels C/C1 according to RTCO-DO160.
ARINC 600 housing has been re-engineered applying the composite approach. Specifications have been drawn and architectures, manufacturing processes and materials have been envisaged, evaluated and a traded-off.
The potential problems in the composite design have been anticipated and alternative countermeasures have been evaluated. A design concept integrating as much as possible of the housing parts has been finally selected, having infusion as manufacturing process in order to keep manufacturing costs as low as possible. Regarding the materials, standard high strength carbon fibres together with aero grade infusion epoxy resin have been selected as main materials for the production of the enclosure parts.
Trials at sample level have been performed in order to explore the different material solutions identified. A mechanical characterisation supporting the FEA of the prototype has been also performed.
Detailed analyses indicate the composite housing is able to withstand the dynamic environment. The selected laminate fulfils both lightness and stiffness requirements. Thermal results obtained are in line with the aluminium counterpart. No problems due to CTE mismatch are foreseen.
The manufactured composite structure successfully passed the vibration testing required by ARINC standards for the present application. Thermal and EMI testing was successfully passed, while some improvements would be necessary for the electrical bonding approach (some of the measurements were slightly over the required threshold).
Compared to the current aluminium approach, significant weight reductions have been obtained: 34 % reduction with respect to the aluminium enclosure; 44 % of reduction if only the modified components are considered – not the commercial parts as hook, handle, etc.