1、1. SCOPE:1.1 Form: This specification covers the material and process requirements forfabricating sandwich radomes having polyimide-resin-impregnated quartz clothshells and polyimide-resin syntactic foam cores.1.2 Application: Primarily as a radar-transparent structure for use as anelectromagnetic w
2、indow up to 315C (600F).2. APPLICABLE DOCUMENTS: The following publications form a part of thisspecification to the extent specified herein. The latest issue of AerospaceMaterial Specifications shall apply. The applicable issue of other documentsshall be as specified in AMS 2350.2.1 SAE Publications
3、: Available from SAE, 400 Commonwealth Drive, Warrendale,PA 15096.2.1.1 Aerospace Material Specifications:AMS 2350 - Standards and Test MethodsAMS 3138 - Coating Materials, Fluorocarbon ElastomericAMS 3684 - Resin, Polyimide, Sealing, High-Temperature Resistant,AMS 3686 - Adhesive, Polyimide Resin,
4、Film and Paste, High TemperatureResistant, 315C (600F)AMS 3619 - Resin, Polyimide, Laminating, High Temperature Resistant,315C (600F)315C (600F), UnfilledAMS 3709 - Syntactic Foam TilesAMS 3751 - Microspheres, Hollow GlassAMS 3803 - Wipes, Cotton, Loosely WovenAMS 3824 - Cloth, Glass, Finished for R
5、esin LaminatesAMS 3847 - Cloth, Quartz, “B“ Stage Polyimide Resin Impregnated,Style 581 Fabric, 315C (600F)AMS 4770 - Brazing Filler Metal, Silver, 50Ag - 18Cd - 16.5Zn - 15.5Cu,1160 - 1175F (625 - 635C) Solidus-Liquidus RangeAEROSPACE MATERIAL SPECIFICATIONAMS3912 REV. A Issued 1974-03Revised 1985-
6、07Reaffirmed 2014-08Superseding AMS3912Radomes, Foam SandwichPolyimide/Quartz Cloth ConstructionRATIONALEAMS3912A has been reaffirmed to comply with the SAE five year review policy._SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical a
7、nd engineering sciences. The use of this report is entirely 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
8、it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2014 SAE InternationalAll 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, mechani
9、cal, photocopying, recording, or otherwise, without the prior written permission of SAE.877-606-7323 (inside USA and Canada)TO PLACE A DOCUMENT ORDER: Tel: Tel: +1 724-776-4970 (outside USA)SAE WEB ADDRESS:Fax: 724-776-0790Email: CustomerServicesae.orghttp:/www.sae.orgSAE values your input. To provi
10、de feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/AMS3912A2.2 ASTM Publications: Available from American Society for Testing andMaterials, 1916 Race Street, Philadelphia, PA 19103.ASTM C273 - Shear Test in Flatwise Plane of Flat Sandwich Construction orSandwich C
11、oresASTM C297- Tension Test of Flat Sandwich Constructions in Flatwise PlaneASTM D790 - Flexural Properties of Unreinforced and Reinforced Plasticsand Electrical Insulating MaterialsASTM D792 - Specific Gravity and Density of Plastics by DisplacementASTM D2520 - Complex Permittivity (Dielectric Cons
12、tant) of Solid ElectricalInsulating Materials at Microwave Frequencies and Temperaturesto 165OCASTM D2584 - Ignition Loss of Cured Reinforced ResinsASTM D2734 - Void Content of Reinforced Plastics2.3 U.S. Government Publications: Available from Commanding Officer, NavalPublications and Forms Center,
13、 5801 Tabor Avenue, Philadelphia, PA 19120.2.3.1 Federal Specifications:2.3.2 Military Standards:O-A-51 - Acetone, Technical GradeTT-M-261 - Methyl Ethyl Ketone (MEK)CCC-C-440 - CheeseclothMIL-STD-794 - Parts and Equipment, Procedures for Packaging and Packing of3. TECHNICAL REQUIREMENTS:3.1 Materia
14、ls: The materials incorporated into the completed radome shall be asspecified herein. The several styles of glass cloth specified shall conformto the applicable requirements of AMS 3824.3.1.1 Polyimide Syntactic Foam Grout Formulation:Component Parts by WeightGlass Microspheres, AMS 3751, Class 1510
15、0Polyimide Resin, AMS 3619140Fine Aluminum Powder, See 8.215l/4-In. (6-mm) Chopped Glass, See 8.37.2Acetone, 0-A-5140N-Methylpyrrolidone (NMP)55SAE INTERNATIONAL AMS3912A Page 2 of 143.1.2 Polyimide Surface Filler Formulation:Component Parts by WeightFine Inorganic Filler, See 8.4 25N-Methylpyrrolid
16、one (NMP) 25Polyimide Resin, AMS 3684 1003.2 Procedure:3.2.1 Mandrel Preparation: The mandrel on which the shell is to be built upshall be cleaned with acetone or with TT-M-261 methyl ethyl ketone (MEK)and coated with an appropriate release agent.3.2.2.1 The mandrel shall be centered in the grinder
17、with a maximum deviation of0.0007 in. (0.018 mm) total indicator reading (TIR) at the nose and0.0010 in. (0.025 mm) TIR at the base.Using the gaging system on the appropriate grinder, bare mandrelreadings relative to the master cam shall be measured to the nearest0.0010 in.(0.025 mm) at the appropri
18、ate stations.3.2.3 General Fabrication Procedures: Fabrication of the radome shell shall beaccomplished in the following sequence:(1) layup and cure the inner skinand solid laminate buildups, (2)bond, grout,and grind precured foamcore,(3)layup and cure the outer skin, and (4)postcure, final grind,tr
19、im, and assemble finished radome (e.g., nose plug, lightning diverters,erosion coating).3.2.3.1 Skin Layup: The warp direction of the resin-impregnated fabric shall beparallel to the radome centerline 10 degrees. Lap joints shall not besuperimposed. Lap joints shall be 0.50 in. 0.25 (12.5 mm 6.2 wid
20、e.The layup temperature shall not exceed 70C(160F)prior to thecuringoperations.3.2.3.2 Layup Debulk: The uncured layup shall be debulked, after each ply orseries of plies is laid up , as required to eliminate wrinkles in thecured skin. Debulking may be accomplished by vacuum bag, wrapping withcord u
21、nder tension,or by use of shrink tape.Temperatures duringdebulking operations shall not exceed 70C (160F).3.2.3.3 Layup Devolatilization: Prior to autoclave cure of the layup, theuncured layup shall be devolatilized to a level which results inlaminates with less than 5% void content after cure and p
22、ostcure in accordancewith this specification.The proper volatiles level willvary with the mass and thermal conductivity of the mold and curedmaterial under the uncured layup. Devolatilization may be accomplished3.2.2Bare Mandrel Calibration:3.2.2.2 SAE INTERNATIONAL AMS3912A Page 3 of 14(Continued):
23、using a vacuum bag or with the layup exposed. The temperature of theuncured layup shall not exceed 70C(160F) during devolatilization,measured by a thermocouple located within the layup no more than one plyfrom the hot surface.3.2.3.4All autoclave cures shall be carried out in a vacuum bag. Thereshal
24、l be at least one thermocouple buried within the layup to be cured,no more than one ply from the mandrel side of the uncured layup, andlocated in the base overtrim. As the coolest thermocouple duringheatup, this shall be the controlling thermocouple. Not less than fourthermocouples shall be taped to
25、 the outer surface of the vacuum bag,located at the base trim, at the nose,and at two intermediate locationsbetween these.These thermocouples shall be insulated from the air withpads of glass insulation. Where vacuum is specified, the vacuumpressure shall be no less than 24 in. (600 mm) of mercury (
26、Hg). Thereshall be three vacuum lines, one at the nose and two at the radome base180 deg apart.3.2.4 Inner Skin Fabrication:3.2.4.1 Layup: Four plies of AMS 3847 resin-impregnated quartz cloth shall belaid up on the mandrel in accordance with 3.2.3.1.3.2.4.2 Preparation for Cure: After debulking in
27、accordance with 3.2.3.2 anddevolatilization in accordance with 3.2.3.3, one ply of unfinished glasscloth,Style 128 or 7628, one ply of release fabric, and one ply ofglass cloth, Style 1584, 184, or 1884, shall be applied in sequence andthe parts shall be vacuum bagged in accordance with 3.2.3.4.3.2.
28、4.3 Cure: After properly placing the part in the autoclave, the part shallbe cured as follows: with the part under a vacuum of not less than24 in. (600 mm) of Hg, the autoclave air temperature shall be raised to120C, -0,+8 (250F,-0,+15) at a rate of 2 - 3 C (4 -5 F) deg permin.,and the autoclave hel
29、d at that temperature until the coolest-partthermocouple reaches 80C (175F). The autoclave air temperature shallbe raised to 15OC8 (330F 15)at a rate of 2- 3 C (4 - 5 F) degper min.; when the coolest-part thermocouple reaches 93C (200F),pressure of not less than 100 psig (690 kPag) shall be applied
30、with allvacuum lines vented to the atmosphere as pressure is applied. When thecoolest-part thermocouple reaches 110C (230F), the autoclave airtemperature shall be raised to 185C, -15, +0 (365F,-25,+0) at a rateof 1 C (2 F) deg per min. and held within that range. When thecoolest-part thermocouple re
31、aches 170C (340F),the part shall be curedfor not less than 2 hr at 170C, -0,+15 (340F, -0, +25). After the2-hr cure, the part shall be cooled under full pressure until thehottest-part thermocouple is below 110C (230F).3.2.3.3Cures:SAE INTERNATIONAL AMS3912A Page 4 of 14SAE INTERNATIONAL AMS3912A Pag
32、e 5 of 143.2.5 Solid Laminate Layup:3.2.5.1 The unfinished glass cloth, Style 128 or 7628, peel ply, shall bestripped from the part in the buildup areas. The stripped areas shallbe brush coated with AMS 3619 polyimide resin and dried at 105C 3(220F 5) for 30 - 60 min., prior to layup.3.2.5.1 Suffici
33、ent plies of Style 7781 glass cloth impregnated with AMS 3619resin shall be laid up over the aft section of the inner skin to obtainthe cured thickness specified on the drawing, plus not less than twoexcess plies. Patterns may be bias-cut relative to the radome axis.The nose area buildup and the aft
34、 buildup tabs shall be cut and laid upas shown on the drawing, using AMS 3847 resin-impregnated cloth.3.2.5.3 The solid builduplayupsshall be debulked in accordance with 3.2.3.2,devolatilized in accordance with 3.2.3.3, vacuum bagged in accordancewith 3.2.3.4, and autoclave cured in accordance with
35、3.2.4.3.The foam tiles shall be fabricated in accordance with AMS 3709 to therequirements of the applicable drawing.The bonding surface of the tiles shall be sanded with No. 400 -600(38 -29 m) grit sandpaper and the dust removed by vacuum.The bondingsurface shall be coated with a thin layer of AMS 3
36、686 polyimide pasteadhesive, and oven dried for45 min. 5 at 105C 3 (220F 5). Onelayer of AMS 3686 polyimide film adhesive, shall be applied to eachbonding surface and oven dried for 45 min. 5 at 105C 3 (220F 5).The prepared tiles shall be stored in moisture-proof bags until they areto be bonded.3.2.
37、7.1 The remaining 128 or 7628 glass peel ply shall be removed from the inner skin.A thin coat of AMS 3686polyimide paste adhesive shall be appliedto the peeled area.The adhesive shall be dried at 105C 5(220F 9) for not less than 60 minutes.3.2.7.2 The prepared tiles from 3.2.6 shall be positioned on
38、 the inner skin inaccordance with the applicable drawing so that there is a gap of0.150 in. 0.030 (3.75 mm 0.75) around each tile.3.2.7.3 One layer of glass bleeder fabric shall be laid over the entireradome/tiles surface,the part shall be vacuum bagged, and a vacuum ofnot less than 24 in. (600 mm)
39、Hg shall be applied.3.2.6 Preparation of Foam Core Tiles:3.2.6.13.2.6.23.2.7 Bonding of Tiles to Inner Skin:SAE INTERNATIONAL AMS3912A Page 6 of 143.2.7.4 The part shall be placed in an autoclave and cured as follows:simultaneously raise the autoclave air temperature to 185 C 3(365F5) at a rate of 1
40、.5 - 2.0 C (2.5 - 3.5 F) deg per min. andraisethepressure to not less than 50 psig (345 kPag). When thecoolest-part thermocouple reaches170C(340F), the part shall bemaintained at 180C 8 (355F 15) for not less than 90 minutes. Thepart shall becooled to 105C(220F)or below under vacuum and at least50 p
41、sig (345 kPag) pressure before debagging.3.2.8 Core Joint Grouting:3.2.8.13.2.8.23.2.8.33.2.8.43.2.8.53.2.8.63.2.8.7Open all joints to 0.19 in.0.06 (4.8 mm 1.5) at the base and taperthe sides to approximately 10deg angle from normal to the radomesurface.Apply a thin coat of AMS 3686 polyimide paste
42、adhesive to all jointsurfaces.Prepare grout mix in accordance with 3.1.1.Pack grout mix into all foam tile joints.Raise radome temperature to 65C3 (150F 5) and hold for60 min.5. Cool to room temperature.One ply of glass release/bleeder fabric shall be placed over all filledjoints. Vacuum bag the par
43、t and apply a vacuum of not less than 24 in.(600 mm) Hg.Heat the radome to 115C5 (240F9) and hold for not less than45 min.; raise radome temperature to 175C 5 (350F 9) and hold fornot less than 90 minutes. Cool the radome under full vacuum to below65C (150F)before debagging.Pregrind: The part shall
44、be centered in the grinder with a maximumdeviation of 0.0007 in. (0.18 mm) TIR at the nose and a maximum of0.0010 in. (0.025 mm) TIR at the base. The foam core window areas shallbe ground to the total wall thickness shown on the drawing, -0.082 in.(-2.05 mm), +O. The solid laminate base area shall b
45、e ground to the totalthickness shown on the applicable drawing. -0.072 in. (-1.80 mm),+0.After grinding, the radome surface shall be vacuumed clean.A thin coat of AMS 3686 polyimide paste adhesive shall be applied toall exterior surfaces of the radome.At least two plies more than the six required fo
46、r the final outer skinshall be laid over that entire surface of the radome using AMS 3847resin-impregnated cloth.3.2.93.2.10.13.2.10.23.2.10.1 Outer Skin Layup:SAE INTERNATIONAL AMS3912A Page 7 of 143.2.10.3 The outer skin layupshall be debulked in accordance with 3.2.3.2,devolatilized in accordance
47、 with 3.2.3.3, and autoclave cured inaccordance with 3.2.4.3.Postcure: The radome shall be fitted with not less than fourthermocouples taped to the outer surface and located at the base, at thenose, and at two intermediate locations between. The thermocouples shallbe insulated from the surrounding m
48、edium to reflect the radometemperature. The radome shall be postcured in accordance with thefollowing schedule, as recorded on the coolest thermocouple. Exposuretimes are minimums and temperatures are 8C (15F):16 hr at 175C (350F), plus24 hr at 205C (400F), plus24 hr at230C (450F), plus24 hr at260C
49、(500F), plus24 hr at 290C(550F), plus8 hr at 315C (600F)3.2.12Final Grind: The radome window area shall be ground to the electricaldesign configuration, determined with a one-horn interferometer. Baseattach area and nose area shall be ground to the dimensional requirementsof the applicable drawing.Coating and Asse
