1、AEROSPACE INFORMATION REPORT AIR5367 Issued 2015-04 Machining of Composite Materials, Components and Structures RATIONALE Currently there is no standard document for machining composite materials. This document provides guidance for these operations. TABLE OF CONTENTS 1. SCOPE 3 1.1 Purpose . 3 2. R
2、EFERENCES 3 2.1 Applicable Documents 3 2.2 SAE Publications . 3 2.3 Other References 3 3. GENERAL . 3 4. PAINT FINISH REMOVAL 5 5. SANDING 7 5.1 Ply Sanding . 7 5.2 Taper Sanding . 7 5.3 Step Sanding . 8 6. DRILLING CARBON EPOXY, FIBERGLASS EPOXY AND CARBON/GLASS HYBRID AND ARAMID FIBER PANELS . 9 6
3、.1 Drill Guides 12 6.2 Cutter Speeds . 13 6.3 Drilling Carbon Epoxy, Glass Epoxy and Carbon/Glass Epoxy Hybrid Panels without Metal Structure Present 14 6.4 Drilling Carbon Epoxy, Glass Epoxy and Carbon/Glass Epoxy Hybrid Panels with Aluminum or Titanium Structure Present . 14 6.5 Drilling Aramid Ep
4、oxy Panels without Metal Structure Present 15 6.6 Drilling Aramid Epoxy Panels with Aluminum or Titanium Structure Present . 15 6.7 Countersinking 16 6.7.1 Countersinking Carbon Epoxy Panels 17 6.7.2 Countersinking Fiberglass and Aramid Epoxy Panels 17 6.8 Deburring Holes and Countersinks in metal .
5、 17 6.8.1 Deburring Carbon and Fiberglass Panels . 17 6.8.2 Deburring Aramid Panels 18 6.9 Hole, Countersink and Trimmed Edge Quality . 18 6.9.1 Holes and Countersinks 18 6.9.2 Trimmed Edges . 19 _ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the stat
6、e 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 therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five yea
7、rs 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 publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means,
8、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: +1 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE v
9、alues your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5367 SAE INTERNATIONAL AIR5367 Page 2 of 25 7. MACHINING AND DAMAGE REMOVAL 19 7.1 Rough Trimming 20 7.2 Band Sawing Carbon and Fiberglass Panels . 20 7.3 Band Sawing Aramid Panels 2
10、0 7.4 Circular Sawing Carbon and Glass Panels . 20 7.5 Circular Sawing Aramid Panels 20 7.6 Reciprocating Sawing Aramid and Glass Panels . 20 7.7 Hole Sawing 20 7.8 Final Trimming 20 7.9 Routing Carbon Panels . 21 7.10 Routing Aramid Panels . 21 7.11 Deburring Trimmed Edges 21 7.12 Hand Sanding . 21
11、 7.13 Disk Sanding . 22 8. MACHINING HONEYCOMB CORE AND METAL BONDED STRUCTURES . 22 8.1 Core Stabilization 24 8.1.1 General . 24 8.1.2 Curing Core into the Component 24 8.1.3 Double Backed Tape . 24 8.1.4 Vacuum Barrier . 24 8.2 Rough Shaping . 24 8.3 Final Contouring and Shaping 25 9. POST MACHINI
12、NG SEALING 25 10. NOTES 25 FIGURE 1 MASKING FOR SANDING OPERATIONS . 6 FIGURE 2 TYPICAL TAPER SANDING TAPER WILL DIFFER DEPENDING ON PLY LAYUP . 8 FIGURE 3 STEP SANDING . 9 FIGURE 4 TYPICAL HOLE DAMAGE (DELAMINATION AND FIBER BREAKOUT) 10 FIGURE 5 TYPICAL COMPOSITE DRILL BITS 10 FIGURE 6 TYPICAL COM
13、POSITE HOLE REAMING BIT . 11 FIGURE 7 TYPICAL COMPOSITE/METAL HYBRID MATERIALS DRILL DATA . 11 FIGURE 8 DRILL GUIDE DUST COLLECTION ATTACHMENT . 12 FIGURE 9 DRILL GUIDES AND BUSHINGS . 13 FIGURE 10 COUNTERSINK MICROSTOPS - CONVENTIONAL AND VACUUM ADAPTED VERSIONS 16 FIGURE 11 TYPICAL COUNTERSINK CUT
14、TER SPEEDS AND FEED RATES 17 FIGURE 12 3 FLUTE CARBIDE COUNTERSINK CUTTER 17 FIGURE 13 TYPICAL CONICAL ABRASIVE DEBURRING TOOL . 18 FIGURE 14 TYPICAL OEM HOLE QUALITY REQUIREMENTS 19 FIGURE 15 CUTTER PLACEMENT FOR ARAMID PANEL ROUTING 21 FIGURE 16 HAND DEBURRING . 22 FIGURE 17 VALVE STEM CUTTERS AND
15、 APPLICATIONS FOR USE 23 FIGURE 18 VALVE STEM CUTTER MACHINING FIXTURE 23 SAE INTERNATIONAL AIR5367 Page 3 of 25 1. SCOPE This SAE Aerospace Information Report (AIR) provides information related to machining of composite materials, components and structures. This document is intended to supplement t
16、he machining processes and guidelines provided in OEM repair manuals and structural repair manuals. It is not intended to supersede the approved data provided in OEM repair documents. 1.1 Purpose This AIR provides background information intended to promote a basic understanding of standard machining
17、 methods that may be referenced in repair documents produced by airlines, airframe manufacturers and engine manufacturers. This AIR is one of a number of AIRs and Aerospace Recommended Practices (ARPs) that cover various aspects of composite repair techniques. 2. REFERENCES 2.1 Applicable Documents
18、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 conflict between the text of this docum
19、ent 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. 2.2 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 1509
20、6-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AIR4844 Composites and Metal Bonding Glossary ARP4916 Masking and Cleaning of Epoxy and Polyester Matrix Thermosetting Composite Materials ARP4977 Drying of Thermosetting Composite Materials ARP4991 Core Re
21、storation of Thermosetting Composite Components ARP5256 Mixing Resins, Adhesives and Potting Compounds ARP5319 Impregnation of Dry Fabric and Ply Lay-Up AIR5431 Repair Tooling 2.3 Other References Original Equipment Manufacturers (OEM) structural repair manuals, standard practices manuals, overhaul
22、manuals, component maintenance manuals, airplane maintenance manuals and other approved repair documents. 3. GENERAL This document provides information for machining of fiber reinforced epoxy airplane structural components during repair. Techniques and required equipment are covered. The basic repai
23、r-related machining steps include: a. Paint finish removal b. Sanding SAE INTERNATIONAL AIR5367 Page 4 of 25 c. Drilling and countersinking d. Trimming e. Damage removal f. Machining of honeycomb core g. Post-machining sealing Use of proper machining techniques and equipment during repair of composi
24、te structures is critical for ensuring that the completed repair has the required structural capability and durability. If these operations are not performed correctly, the repair may not be structurally acceptable. Typical composite panel fiber reinforcements are: carbon, aramid (e.g., Kevlar), and
25、 glass (commonly referred to as fiberglass). The machining techniques for these typical composite materials are similar, but minor differences exist, such the style of cutting tool or drill bit. Machining of composites differs from machining of typical metals. High-speed steel drill bits and other c
26、utting tools are normally used to machine aluminum and mild steel alloys. However, composite materials are abrasive and can cause higher drill and cutter wear than is experienced in machining of metals. Therefore, the required bits and cutting tools for machining of composites are different than tho
27、se typically used for machining of metals. Further, it is important to change drill bits and cutters before they become dull. Using worn drill bits and cutters is a common cause of damage when drilling and machining composites. The cost of changing a drill bit or cutter is small compared to the cost
28、 of re-work that may be required due to a damaged hole or other machined surface. Components containing carbon fibers are machined similar to those containing glass fibers except that carbide or diamond abrasive coated cutting tools are preferred for components containing carbon. Carbide tipped and
29、diamond abrasive coated tools stay sharp through many cutting operations. Components containing aramid fibers (including hybrid panels contain aramid and carbon fibers) are difficult to machine using conventional drill bits and cutting tools. Use of conventional tools can produce a fuzzy appearance
30、on the machined surface. This results from what is essentially a tearing of the fiber as it is machined. Specialized cutting tools will reduce or eliminate fiber fuzzing, fiber breakout and interply delamination. These special tools are designed to grab the fibers and stretch them prior to cutting.
31、When drilling or machining hybrid panels that contain aramid and carbon fiber, an aramid fiber cutter is to be used. However, the tool life should be monitored closely because the carbon fibers will dull the cutter quickly. The typical cutters that are preferred for machining carbon fiber materials
32、are not effective for preventing fuzzing in aramid components. Additional factors that affect a composite laminate at the edge of the cut are feed rate and tool rotation speed, especially during final drilling and cutting operations. Maximizing cutting tool life is also dependent upon choosing the a
33、ppropriate feed rate and tool rotation for the material being machined. Since the quality of the cut degrades as the tool wears the finish characteristics of each hole or cut should be continuously monitored during machining. Cutting tools should be changed before an unacceptable cut surface is prod
34、uced. For hand held operations the number of cuts or holes that can be made before changing the tool can vary significantly. Using carbide and diamond abrasive tools to machine carbon and glass fiber materials significantly improves the number of cuts or holes that can be produced before the cutter
35、needs to be changed. The epoxy resin component of the composite laminate has a low thermal conductivity and using worn cutters or too high of a feed rate can result in localized overheating or burning that can damage the laminate. Worn cutters can also result in backside fiber breakout and delaminat
36、ion. The OEM repair manuals contain guidelines for tool type, material feed rates, lubricant use and tool rotation speeds that are known to produce satisfactory results for specific applications. To prevent damage, it is recommended to practice unfamiliar machining procedures on scrap pieces of comp
37、osite material before using them on the component being repaired. This can prevent having to perform unnecessary repairs caused by improper machining techniques. SAE INTERNATIONAL AIR5367 Page 5 of 25 WARNING: During machining operations personal protective equipment including eye protection should
38、be worn by all personnel in the immediate area to prevent breathing dust created during the machining process. Health and safety procedures should be followed at all times. CAUTION: Carbon dust can become electrically conductive. All electrical equipment and connectors in the local area should be co
39、vered to prevent carbon dust from settling in those areas. Both carbon and fiberglass dust are highly abrasive. Care should be taken to keep dust from settling on mechanisms, actuators or other moving parts. CAUTION: Many paint materials are epoxy based and are similar in composition to the epoxy re
40、sins that make up the component surface or laminate. During paint removal operations, use extreme care to remove only the paint, and not damage the underlying laminate. In some instances, high performance finishing materials may be tougher to sand than the underlying surface of the component. Use ex
41、treme care to avoid exposing the fibers in the component surface. If the fibers are damaged, it may be necessary to expand the size of the repair as a result of fiber damage created during paint removal. CAUTION: Chemical paint strippers can damage the resin matrix of the composite material. Exposur
42、e to chemical strippers that soften epoxy paints can cause similar damage to the epoxy resin in the composite component. Chemical stripping materials should NOT be applied to composite components except where OEM approval and processes are provided. 4. PAINT FINISH REMOVAL Sanding procedures used to
43、 remove paint and prepare the surfaces of composite materials for bonding are common between the different fiber reinforcements. Paint removal consists of removing any exterior paint or other materials from the surface where a bonded composite repair will be installed. Clean the area where the paint
44、 will be removed in accordance with the repair document or ARP4916, Composite Cleaning Method 4 or 5. Apply masking or protective tape around the area to protect the existing paint that will not be removed. Refer to the repair document to determine the size of the area to be sanded, which will be ba
45、sed on damage size, required number of repair plies, ply overlap width, etc. Also refer to the repair document or ARP4916, Masking Method 5 for masking procedures using a protective tape. Place the tape around the perimeter of the area where the paint will be removed to protect the surrounding finis
46、h. It is important to remove enough paint to ensure all repair materials are placed directly on the abraded composite material. Overlapping the repair materials onto incompletely removed exterior finishes and paints will produce a structurally unsatisfactory repair. An example of protective masking
47、detailing the areas requiring paint removal and taper sanding is provided in Figure 1. SAE INTERNATIONAL AIR5367 Page 6 of 25 FIGURE 1 - MASKING FOR SANDING OPERATIONS Using an air powered sander, or equivalent, remove the paint in the masked off area using the OEM specified procedure. If no procedu
48、re is specified by the OEM, a medium or fine abrasive pad or paper is typically used. An abrasive pad is preferred when removing exterior finishes as there is less risk for fiber damage using an abrasive pad. Paint removal operations are intended to remove all topcoat paint, primer and surfacing mat
49、erials from areas where adhesive bonds will be located. Ease of finish removal is affected by the overall smoothness of the component surface. A composite component normally has two different types of surfaces that are referred to as the tool side and bag side surfaces. The tool side surface is generally smoother than the bag side because it was cured against a
