1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2015 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5552AEROSPACEINFORMATION REPORTAIR5552Issued 2010-10 Reaffirmed 2015-11 Develo
5、pment and Qualification of Composite Landing Gears RATIONALE AIR5552 has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS 1.SCOPE 31.1Purpose . 31.2Application . 31.3Composite Design References . 31.4Further development of this AIR . 32.REFERENCES 42.1SAE Publication
6、s . 42.2FAA Publications . 42.3Other Publications . 43.APPROACH 44.REQUIREMENTS . 64.1Composite Landing Gear Requirements 64.2Environmental Considerations 75.DEVELOPMENT APPROACH 85.1Means of Compliance . 85.1.1Enhanced Safe Life Method 85.1.2Damage Tolerance Method 85.2Reliability . 86.DAMAGE TOLER
7、ANCE . 96.1Characterization of Damage . 96.2Inspections 107.THREAT ASSESSMENT 107.1Intrinsic Flaws . 117.1.1Delamination . 117.2Manufacturing Process Induced Damage . 117.3Service Damage 127.4Maintenance Induced Damage . 127.5Discrete Source Damage 128.MATERIAL AND PROCESS CHARACTERISATION . 128.1Ma
8、terial and Process Specification . 138.2Coupons 138.3Elements . 138.4Manufacturing Location . 139.COMPONENT DESIGN 139.1Analysis . 139.2Protection from Environments . 1310.HYBRID ASSEMBLY 1411.COMPONENT TESTING 1411.1Strength Evaluation . 1411.1.1Limit Load 1411.1.2Ultimate Load 1511.2Fatigue Evalua
9、tion 1511.2.1Fatigue Spectrum 1511.2.2Spectrum Truncation . 1511.3Endurance Evaluation . 1511.4Factors 1611.4.1Environment 1611.4.2Fatigue 1612.CONTINUING AIRWORTHINESS 1612.1Repairs 1612.2Overhaul 16SAE INTERNATIONAL AIR5552 2 OF 161. SCOPE This information report provides general guidance for the
10、design considerations, qualification in endurance, strength and fatigue of landing gear using composite components as principle structural elements. The information discussed herein includes the development and evaluation of design data considering: the potential for imbedded manufacturing defects,
11、manufacturing process variations, the component operating environment, potential damage threats in service, rework and overhaul, and inspection processes.This AIR mainly discusses the use of thick composites for landing gear structural components. Considerations and recommendations provided in this
12、AIR may therefore differ greatly from considerations and recommendations found in widely accepted composite design references such as CMH-17 and Advisory Circulars such as AC 20-107(B). 1.1 Purpose The purpose of this AIR is to provide general guidance in the qualification of composite components fo
13、r landing gears. Compliance with this report is not considered approval for installation on any category aircraft or helicopter. The Certifying Authority for the platform for which the equipment is intended should be consulted for concurrence with the approaches proposed herein as an acceptable qual
14、ification demonstration for composite landing gear components. 1.2 Application This AIR is applicable to the qualification of the composite landing gear structural elements in strength, fatigue and endurance. The current version of this document focuses on the use of Polymer Matrix Composites, but m
15、ight also be applicable for other composite materials such as Metal Matrix Composites although they are not explicitly discussed herein.Compliance with this information report by manufacturers, installers, and users may be used as a means of assuring that the equipment will have the minimum capabili
16、ty to satisfactorily perform its intended function(s). 1.3 Composite Design References In the development of this AIR, close interaction is sought with other composite guideline development such as within the CMH-17 and AC 20-107 committees.It should be noted that the majority of documentation on co
17、mposite materials concerns thin walled structures. The application in landing gear principle structural element primarily focuses on thick walled structures. 1.4 Further development of this AIR It is recognized that the guidance provided in this document on composite application to a landing gear pr
18、inciple structural element is general in nature and limited in scope. It is the intent that this document will be further developed over time where active feedback from industry and authority specialists is sought to expand the scope to other category aircraft and provide more specific guidance to c
19、omposite component development in landing gear principle structural elements. SAE INTERNATIONAL AIR5552 3 OF 162. REFERENCES The following publications form a part of this document specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be
20、 the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws or regulations unless a specific exemption has bee
21、n obtained.2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AIR1494 Verification of Landing Gear Design Strength ARP1311 Landing Gear Structures and Mechanism
22、s ARP5914 Landing Gear Fatigue Spectrum Development for Part 25 Aircraft ARP5644 Impact Testing of Aircraft Landing Gear 2.2 FAA Publications Available from Federal Aviation Administration, 800 Independence Avenue, SW, Washington, DC 20591, Tel: 866-835-5322, www.faa.gov.Title 14, Code of Federal Re
23、gulations (14 CFR) part 25 Airworthiness Standards: Transport Category Airplanes (25.301 through 307, 25.471 through 25.519, 25.571, and 25.723 through 25.729) Advisory Circular (AC) 20-107B, Composite Aircraft Structure Metallic Materials Properties Development and Standardization (MMPDS), Version
24、3, 2006 DOT/FAA/AR-03/19 Material Qualification and Equivalency for Polymer Matrix Composite Material Systems 2.3 Other Publications CMH-17-F Department of Defense Handbook, Composite Materials Handbook AC23-13A Fatigue, Fail Safe, and Damage tolerance evaluation of metallic structure for normal, ut
25、ility acrobatic and commuter category airplanes AC25-571-1B Damage tolerance and fatigue evaluation of structure AFS-120-73-2 Fatigue evaluation of wing and associated structure on small airplanes, May 1973. 3. APPROACH In order to define the strength and fatigue capabilities of composite components
26、, its properties must be determined by structural analysis and/or test. Typically, a pyramid or building block approach is employed where analyses are combined with tests at various levels of structural complexity. Going up this pyramid, the number of test specimens decreases, while the test complex
27、ity increases. During a program, these building block levels are linked with supporting technologies and design considerations. This is depicted in Figure 1. SAE INTERNATIONAL AIR5552 4 OF 16FIGURE 1 - BUILDING BLOCK APPROACH FROM CMH-17 Simple coupons or specimens are tested at the lowest level to
28、statistically determine the material strength and stiffness allowables. Once the simple coupon values are determined, more complex multi-directional coupon properties are developed by test until ultimately the component level properties are defined. The building block approach should include the cri
29、tical service environmental conditions in deriving the material properties and allowables. The number of tests should be sufficient to ensure statistically significant results. Because of the complex, anisotropic mechanical response of composite materials, modifying factors as traditionally used in
30、metal components, like stress concentration factors found in handbooks, cannot be used. Instead the properties of critical details are substantiated by using structural element or sub-component tests representing local composite architecture and design details. Also scaling of structural elements as
31、 seen in metal design solutions is generally not possible in composite designs. Instead, extensive testing and analyzing is required. Although the building block approach is widely acknowledged, details are far from universal and may be program and component specific. Figures 2 and 3 depict a typica
32、l building block strategy for aircraft defined in CMH-17-F.For more information on the Building Block approach, please refer to CMH-17. FIGURE 2 - TYPICAL BUILDING BLOCK APPROACH FOR AIRCRAFT (FROM CMH-17) SAE INTERNATIONAL AIR5552 5 OF 16FIGURE 3 - BUILDING BLOCK APPROACH FOR AIRCRAFT LANDING GEAR
33、(ADAPTED FROM CMH-17) 4. REQUIREMENTS 4.1 Composite Landing Gear Requirements The regulatory requirements applicable to the landing gears of commercial transport aircraft are the same as for metal landing gears and are defined by CFR 14 Part 25. For instance, the load cases for landing gears on Part
34、 25 aircraft are defined in sections 471 through 519, and 723 through 729. Besides these mandatory requirements, program specific requirements may be imposed by the customer. The following items form the basic requirements for composite structural landing gear components: a. Components likely contai
35、ning damage or defects smaller than or equal to the acceptable limits per specification during manufacturing inspections and service inspections must withstand the ultimate load after cyclic loading to an appropriate detection interval and not impair operation of the landing gear component for its d
36、esign life using an appropriate factor b. Components containing damage that is detectable during maintenance inspections must withstand limit load, which may be applied following repeated service loads occurring during an inspection interval using an appropriate factor c. All damage that lowers comp
37、onent strength below ultimate load must be repaired when found d. Components damaged from an in-flight, discrete source that is evident to the crew must withstand loads that are consistent with continued safe flight and landing e. Any component with damage that is repaired must withstand ultimate lo
38、ad f. If cyclic loading is shown to degrade the load carrying capability of the component, static tests up to ultimate load should be performed on specimens and/or elements and/or components that have accumulated prior cyclic loading g. If environmental exposure is shown to degrade the load carrying
39、 capability of the component, static tests should be performed on specimens and/or elements and/or components that have accumulated prior environmental exposure SAE INTERNATIONAL AIR5552 6 OF 16Based on these basic requirements, it follows that a large portion of the Proof of Structure testing demon
40、strations must be done using both damaged, service and imbedded, repaired specimens and specimens that have accumulated prior environmental exposure and that the supporting analyses must use substantiated degraded strengths. 4.2 Environmental Considerations The critical environmental limits should b
41、e established early in the program, as they may affect results at all building block levels. Environments to consider for landing gear components include, but are not limited to: x Ultra Violet Rays x Humidity x Temperature x Sand and Dust Abrasion x Salt Fog x Fungus x Fluids Temperature and humidi
42、ty play a key role in the certification of composite components, because many composites are sensitive to temperature and moisture. These parameters can vary substantially during the life of a composite component, so hydro-thermal cycling needs to be considered.High temperatures due to high energy b
43、raking needs to be considered for components in close proximity to the wheel brakes. Fluids generally to be considered for landing gear components are: x Hydraulic fluids such as MIL-PRF-83282, MIL-H-5606, SKYDROL, etc. x Lubricants x Disinfectants x Fuels x Solvents and cleaners (water, water and s
44、oap, alkaline cleaners, MIBK, MEK, Toluene etc.) x Electronic equipment coolant such as polyalphaolefin x Fire extinguishing materials such as bromotrifloromethane x De-icing fluids such as propylene glycol and isopropyl alcohol x Runway de-icers For strength and fatigue substantiation of thick wall
45、ed landing gear components, it may take a relatively long time to establish saturation levels that are representative for in service, or equal to the maximum attainable level for coupons. Thick wall composite structures may be less susceptible to the humid environments than thin structures, since it
46、 will take longer for saturation levels to become high throughout the thicker composite structure. For this reason, knock down factors defined using a specimen with lesser thickness might be too conservative for knock down factors for thick composites (see section 11.4). The level of saturation at e
47、ach level of test for thick walled composites should be reviewed in detail and substantiated with a rationale based on test data and experience. For hybrid assemblies (see section 10), the effects of these environments on the interaction of the sub-assemblies in strength, endurance and fatigue need
48、to be demonstrated, considering effects like corrosion and thermal expansion. SAE INTERNATIONAL AIR5552 7 OF 165. DEVELOPMENT APPROACH 5.1 Means of Compliance It is the nature of composite structural components that a combination of safe life and damage tolerant philosophies be employed. The crack initiation and growth properties observed in metals during the service loading life of the gear are not typical in composite components. However, the composite must be shown to be capable of retaining its load carrying capability through
