1、AEROSPACE RECOMMENDED PRACTICEARP5144Issued 2000-03Heat Application for Thermosetting Resin CuringTABLE OF CONTENTS1. SCOPE .41.1 Purpose .42. APPLICABLE DOCUMENTS42.1 SAE Publications .42.2 ASTM Publications 52.3 Other Publications .52.4 Applicable References.53. GENERAL REQUIREMENTS.54. CURING CYC
2、LE.64.1 Definition64.2 Curing Profile .74.2.1 Heating Phase .74.2.2 Curing Phase .84.2.3 Cooling Phase .84.3 Examples of Curing Cycles84.3.1 Single Step Curing Cycle.84.3.2 Multiple Step Curing Cycle.94.4 Repair Actions Following Equipment Failure .105. HEAT (THERMAL) TRANSFER .115.1 Conduction. 115
3、.2 Convection.12Reaffirmed 2011-11RATIONALEThis document has been reaffirmed to comply with the SAE 5-year Review policy. 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
4、voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, 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. SA
5、E invites your written comments and suggestions.Copyright 2011 SAE International All rights reserved. No part of this publication 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 pr
6、ior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit h
7、ttp:/www.sae.org/technical/standards/ARP5144Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 2 -TABLE OF CONTENTS (Continued)5.3 Radiation135.4 Heat Diffusion 136. TEMPERATURE MEASUREMEN
8、T WITH THERMOCOUPLES 146.1 Definition 146.2 Temperature Measurement146.2.1 Direct Methods.146.2.2 Potentiometer Methods156.2.3 Digital Voltmeters .156.2.4 Temperature Indicators 166.3 Standard Thermocouples.166.4 Manufacturing of Thermocouples 176.4.1 Thermocouple With Welded Joint 176.4.2 Thermocou
9、ple Manually Twisted Before Welding186.4.3 Thermocouple With Plate Connection .186.4.4 Extension Cables .196.5 Verification of Thermocouples196.6 Installation of Thermocouples 206.6.1 Installation of Thermocouples for Skin Repair .216.6.2 Installation of Thermocouples for Core Bonding226.6.3 Install
10、ation of Thermocouples for Co-curing of Skin/Core Assemblies 247. HEATING DEVICES .247.1 Heat Blankets.247.1.1 Verification of Heat Blankets With Infra Red (IR) Sensor: Method 1.257.1.2 Verification of Heat Blankets by Thermal Imaging: Method 2 .267.1.3 Verification of Heat Blankets by Resistance Me
11、asurement: Method 3287.1.4 Requirements for Repaired Heat Blankets.287.1.5 Installation of Heat Blankets 287.1.6 Caution for Application.307.2 Radiant Heaters .307.2.1 Calibration of Radiant Heaters.307.2.2 Installation of Radiant Heaters.327.2.3 Caution for Application.327.3 Hot Air Blower 327.3.1
12、Hot Air Blower Installation327.3.2 Caution for Application.337.4 Ovens.337.5 Autoclaves .347.6 Caution for Application - Ovens and Autoclaves357.7 Typical Steps in Oven and Autoclave Curing .367.8 Hot Bond Console (Curing Console)387.8.1 Caution for Application.38Copyright SAE International Provided
13、 by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 3 -TABLE OF CONTENTS (Continued)8. REPAIR CURING398.1 Process Control .398.2 Cure Records.39Copyright SAE International Provided by IHS under license with SAENot for ResaleN
14、o reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 4 -1. SCOPE:This SAE Aerospace Recommended Practice (ARP) describes standard methods of heat application to cure thermosetting resins for commercial aircraft composite repairs.The methods described in this document sha
15、ll only be used when specified in an approved repair document or with the agreement of the Original Equipment Manufacturer (OEM) or regulatory authority.1.1 Purpose:The purpose of this document is to provide a number of standard heat application methods that may be referenced in repair documents pro
16、duced by airlines or airframe and engine manufacturers.This document is one of several in support of other procedures required to perform composite repairs, intended for use throughout the commercial aircraft industry. These include AIR4844, AIR4938, AIR5278, ARP4916, ARP4991 and others incorporated
17、 herein.2. APPLICABLE DOCUMENTS:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflic
18、t 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 and regulations unless a specific exemption has been obtained.2.1 SAE Publications:Available from SAE, 400 Commonwealth Drive, Wa
19、rrendale, PA 15096-0001.AIR4844 Composite and Metal Bonding GlossaryAIR4938 Composite and Bonded Structure Technician/Specialist: Training DocumentAIR5278 Composite and Bonded Structure Engineers: Training DocumentAIR5431 Tooling for Composite RepairsARP4916 Masking and Cleaning of Epoxy and Polyest
20、er Matrix Thermosetting Composite MaterialsARP4977 Drying of Thermosetting Composite MaterialsARP4991 Core Restoration of Thermosetting Composite MaterialsARP5143 Vacuum Bagging of Thermosetting Composite RepairsAMS 2750 PyrometryCopyright SAE International Provided by IHS under license with SAENot
21、for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 5 -2.2 ASTM Publications:Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM D 2471 Gel Time and Peak Exothermic Temperature of Reacting Thermosetting ResinsASTM E 220 Calibrati
22、on of Thermocouples by Comparison TechniquesASTM E 230 Temperature - Electromotive Force (EMF) Tables for Standardized ThermocouplesASTM Manual Series: MNL12-Manual on The Use of Thermocouples in Temperature Measurement2.3 Other Publications:Available from BSI, 389 Chiswick High Rd., London W4 4AL,U
23、K.AECMA PREN 6043 Aerospace Series Thermosetting Resin Systems Test Method Determination of Gel Time and ViscosityIEC 584-1 Thermocouples Parts 1-8: Reference Tables Second Edition2.4 Applicable References:Original Equipment Manufacturers (OEM) Manuals3. GENERAL:a. Heat application to thermosetting
24、resins accelerates the curing process and has to be applied in accordance with the manufacturers instructions and the repair design.b. Several heating devices such as heat blankets, hot air generators, heating lamps, ovens and autoclaves are available for repairs.c. The choice of heating devices for
25、 the curing of a repair depends on the equipment available, the geometry of the component, the restrictions of the repair environment, and the required cure accuracy.d. Composite repairs requiring elevated temperature curing need to be controlled, in accordance with the repair schedule. Refer to 8.1
26、 and 8.2 for requirements on recording of cure data.e. Throughout this document rounding up or down has been made when converting units of measurement. In instances where it would not be appropriate to do this, then a precise conversion is applied.Copyright SAE International Provided by IHS under li
27、cense with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 6 -3. (Continued):Set out below are some examples:100 C (212 F) i.e., exact conversion used120 C (250 F) rounded up from 248 F180 C (350 F) rounded down from 356 F300 mm (12 in) rounded up
28、from 11.8 in4. CURING CYCLE:4.1 Definition:Curing of thermosetting resins is by chemical reaction. For some resin systems the curing may take place at 15 to 20 C (60 to 70 F) over a time span of between 8 h to 7 days depending on the resin. The curing process for these room temperature curing system
29、s can be accelerated by the application of heat, typically 40 to 80 C (100 to 180 F). This reduces the curing time which has obvious commercial advantages and improves mechanical and chemical properties. The actual temperature used will be governed by the specific resin chosen. Curing for these syst
30、ems should not be attempted below 15 C (60 F) because of the risk of undercure. It should be noted that once mixed, resins will continue to cure even below 15 C.Other resin systems will not cure satisfactorily at room temperature but require elevated temperature, typically 93 C (200 F), 120 C (250 F
31、), or 180 C (350 F) to achieve full cure.During the curing process, compaction is necessary, in order to reduce the porosity level and facilitate vertical bleeding when required. Refer to ARP5143.The major process parameters which define a repair cure cycle are:a. Temperatureb. Pressurec. TimeThese
32、process parameters, particularly time/temperature cycles, are defined during resin qualification. They shall be applied within stated tolerances.Depending on the resin and/or the repair instructions, stepped curing may be necessary. In this procedure curing takes place in a series of steps where the
33、 temperature is held at a defined value for a specified time and then raised to a higher value for a further period of time, until the final cure temperature is achieved.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without li
34、cense from IHS-,-,-SAE ARP5144 - 7 -4.2 Curing Profile:Typical curing cycles involve three major phases:a. Heating Phase: Heat-up at the defined rate to the required curing temperature.b. Curing Phase (Hold Phase): Stabilized temperature period for minimum time to achieve the required cure.c. Coolin
35、g Phase: Cool down at the defined rate.Each phase of the curing cycle must stay within defined temperature and time tolerances to obtain uniform curing.The resin cure cycle is stated in the repair instructions.4.2.1 Heating Phase: The heat-up rate is generally defined in degrees/minute with maximum
36、and minimum values. A fast heat-up rate is desirable to reduce processing times which from a repair standpoint is a benefit if rapid turn around times are needed. But it shall be slow enough so that gross temperature differences do not cause uneven curing and related part warpage.Typical heat-up rat
37、es for epoxy curing are 2.5 to 4.5 C (4.5 to 8 F) per minute for small parts and 1.5 to 2.5 C (2.5 to 4.5 F) per minute for large parts.The resin behavior will determine the maximum heat-up rate, to take into consideration the following points:a. Exothermic Reaction: An exothermic chemical reaction
38、is one in which heat is generated during the reaction. The heat can be considerable and must be contained within acceptable limits.b. Resin Viscosity Changes: In the early stages of cure the resin reaches a low viscosity. During this period it can wet the surfaces to be bonded, will fully wet out th
39、e fibers, and flow into crevices or surface variations. As the curing process takes place, cross linking of the resin will occur. At the gel point, the resin changes from a fluid to a solid state. On completion of curing, the material is a hard solid.c. Volatile Extraction: This is an important phas
40、e in the cure cycle. It is essential to vent/extract volatiles, which are a by-product of the chemical reaction, or an unacceptable porous structure could result.d. Gelation: This is an important stage in the cure of the resin. It is the point in a resin cure when the viscosity has increased to a po
41、int such that it barely moves when probed with a sharp instrument. At this stage, the cure is well advanced.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 8 -4.2.1 (Continued):The mini
42、mum heating rate is defined to avoid excess bleeding before gelation.To avoid over heating the repair, close monitoring is necessary. Consideration should be given to reducing the heat-up rate as the temperature of the part nears the cure (hold) temperature. This will assist in preventing overshoot
43、of the cure temperature.Equipment capability and heat sinks are factors that can affect the heat-up rate, resulting in thermal gradients across the repair. To determine whether thermal gradients may occur, a heat survey should be conducted prior to curing the repair. Refer to 5.4.4.2.2 Curing Phase
44、(Hold Phase): Measurement of cure time (cure phase or hold phase) commences when all repair thermocouples are within the required temperature band. During the cure phase all thermocouples shall remain within this temperature band. It is important to adjust the heat input to bring the temperature wit
45、hin this band as quickly as is practical. Consideration may have to be given to scrapping the repair if this cannot be achieved within a reasonable and practicable time. An alternative repair route may then have to be considered.The cure time (hold time) is stated in the repair instruction.4.2.3 Coo
46、ling Phase: Cooling may start when the stabilized period (curing or hold phase) is complete. The cooling rate is stated in the repair instruction.High cooling rates should be avoided because they increase the thermal gradient and may induce transverse micro-cracking in the repair.Typical maximum coo
47、ling rates are 4.5 C (8 F) per minute for small parts and 2 C (4 F) per minute for large parts.4.3 Examples of Curing Cycles:4.3.1 Single Step Curing Cycle (Figure 1): In this example heat and vacuum are applied simultaneously.Copyright SAE International Provided by IHS under license with SAENot for
48、 ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP5144 - 9 -FIGURE 1 - Single Step Curing Cycle4.3.2 Multiple Step Curing Cycle (Figure 2):Steps 1, 2, 3 - Heat-up phase.Step 4 - Curing phase (hold phase).Step 5 - Cool-down phase.An intermediate step (step 2) may be required to prevent excess resin flow during heating up phase. The duration of the step is timed to allow resin gelation to occur.Vacuum is applied simultaneously with heating.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted w
