1、l. t MILHDBK-793 (AR) MILITARY HANDBOOK 6 November 1989 NONDESTRUCTIVE TESTING TECHNIQUES FOR STRUCTURAL COMPOSITES I AMSC N/A AREA NOTI r. O DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without
2、 license from IHS-,-,-FOREWORD - I. This military handbook is approved for use by all Activities and Agencies of the Department of the Army and is available for use by all Departments and Agencies of the Department of Defense. 2. Beneficial comments (recommendations, additions, deletions) and any pe
3、rtinent data that may be of use in improving this document should be addressed to: Commander, US Army Armament Research, Development, and Engineering Center, Am: SMCAR-BAC- iii Page iv iv V 1-1 1-1 1-1 1-1 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-3 1-3 2-1 2-1 . 2-1 2-2 2-2 2-2 2-2 2-3 2-3 2-3 2-3 2-3 2-3 2-3
4、2-4 2-4 2-4 2-4 2-4 2-4 3-1 3-2 3-3 3-3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3-3.1.1 3-3.1.2 3-3.2 3-3.3 3-3.4 3-4 3-4 .I 3-4.1.1 3-4.1.2 3-4.1.3 3-4.1.4 3-4.1.5 3-4.2 3-5 . MIL-HDBK-793(AR) CONTENTS (contd) Control of Prepregs . Cure Moni
5、toring . SANDWICH CONSTRUCTION ADHESIVE BONDING NEW DEVELOPMENTS IN IN-PROCESS NDT . : END-ITEM NONDESTRUCTIVETESTING FINAL INSPECTION . Radiographic Inspection . Ultrasonic Inspection Acoustic Emission Inspection Mechanical Impedance Inspection . ; Thermal Inspection . IN-SERVICE NONDESTRUCTIVE TES
6、TING NEW DEVELOPMENTS IN END-ITEM NDT . REFERENCES BIBLIOGRAPHY APPENDIX A . APPENDIX B . GLOSSARY INDEX ? LIST OF IELUSTRATIONS Figure No . Tit le 1-1 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-1 I 3-12 3-13 3-14 3-15 3-1 6 Typical Sandwich Construction (Honeycomb) . Design Team Concept for Structu
7、re Reliability Various Configuration Set-ups of Gamma Backscatter Gages . Dual Traversing Frames With Color CRT Display for Gamma Backscatter Gages Composite Main Rotor Blade Inspection by Fluoroscopic Radiography Gamma Backscatter Gage Control Laboratory for Fluoroscopic Radiography Showing Real-Ti
8、me Inspection of Honeycomb Panel . Pulsed Echo Ultrasonic Inspection Water Squirter Used to Couple the Ultrasonic Signal to the Part in Through-Transmission Ultrasonics . Multiple Squirters for the Inspection of Large Parts BondaScope 2100 Standing Wave Ultrasonic Inspection Instrument Variety of Pa
9、rts Awaiting Fluoroscopic Radiographic Inspection Harmonic Bond Tester With the Vibrating Pin Probe-Left Front The NovaScope 2000 Ultrasonic Inspection Equipment . i . Acoustic Emission Testing of Aerial Lift Trucks Showing the Use of a Tie-Down to Stress the Boom . Acoustic Emission Testing of a Co
10、mposite Helicopter Rotor Blade . Acoustic Emission Sensors Located on the Boom of an Aerial Lift Truck During Test LIST OF TABLES Table No . Ede 3- 1 Consensus Specifications for Incoming Materials . 3-3 Final Inspection Techniques for Specific Defects . 3-2 Defects Detected by Various NDT Methods 3
11、-3 3-4 3-5 3-5 3-6 3-6 3-7 3-7 3-7 3-10 3-10 3-10 3-11 3-13 3-14 3-16 A- 1 B-1 G- 1 1-1 Page 1-3 3-1 3-4 3-4 3-5 3-7 3-8 3-8 3-9 3-9 3-10 3-10 3-11 3-11 3-12 3-13 3-13 Page 3-3 3-3 3-7 0 iv Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF .ABB
12、REVIATIONS AND ACRONYMS AE = acoustic emission AMS = Aerospace Materials Specifications CRT = cathode-ray tube DIN = Deutsches Institute for Normung e.u. IS0 International Organization for Standardiza- NASA National Aeronautics and Space Administra- ASTM = American Society for Testing and Materials
13、EDAX = energydispersive X ray tion tion NDE = nondestructive evaluation ND1 = nondestructive inspection; nondestructive in- NDT = nondestructive testing vestigation NTIAC = Nondestructive Testing Information Analysis Center PAN = polyacyrlonitrile PMR = polymerization of monomer reactants RP = reinf
14、orced plastics SAE = Society of Automotive Engineers and Process Engineering SAMPE = Society for the Advancement of Materials SEM = scanning electron microscope SMC sheet molding compounds SNDT = shearographic nondestructive testing SPI = Society of the Plastics Industry SQUINT = Surface Quality Uni
15、t for Inspection by Non- STEM = scanning transmission electron microscope destructive Testing V Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-773 ND m 7777770 0035777 O -3 - CHAPTER 1 INTRODUCTION The purpose and scope of this handbook are
16、 discussed. The term composife materials is defined, and the roles of components of these materials-reinforcements, glass fibers, graphite fibers, aramid fibers, and polymeric matrices-are discussed. Solid laminates and sandwich constructions are defined and discussed. 1-1 PURPOSE The purpose of thi
17、s handbook is to educate the reader as to the nature of nondestructive testing of fiber-reinforced polymeric materials. Metal-matrix com- posite materials are another subject and will not be addressed here. The intent is to advise the reader about the various techniques available for use during the
18、inspection of the raw materials and incoming compo- nent materials, for inspection during fabrication, and for final inspection and in-service monitoring to detect damaged and/ or degraded structures. 1-2 SCOPE Nondestructive testing is the testing of materials or structures without causing failure
19、of the item being tested. There are three acronyms that are in general usage: nondestructive testing (NDT), nondestructive evaluation (NDE), and nondestructive inspection (NDI) (or nondestructive investigation (NDI). These terms are used by various authors to describe the same basic types of testing
20、. NDT is the more general term, ND1 (inspection) is preferred by the quality control engineer, and NDE and ND1 (investigation) are preferred by the research scientist. This handbook briefly describes the materials of in- terest, namely, the organic or polymeric matrix-fiber- reinforced composites. T
21、he various nondestructive techniques available are described in a manner that otlines the techniques. However, this handbook is not intended for use as an operators manual for the tech- niques discussed. This handbook covers the testing that can and should be carried out on (1) incoming materials, s
22、uch as pre- pregs, resins, and fibers, to help build quality assurance into the subsequent parts, (2) the types of tests that can be used during fabrication and on the final product, and (3) in-service use of NDT. In-service use of NDT covers the problems related to in-service testing in evaluating
23、such properties as reliability, durability, and life expectancy of a fiber-reinforced composite by nonde- structive means. Further, an attempt will be made to alert the reader to new and promising techniques that are being de- veloped. 1-3 DEFINITIONS 1-3.1 COMPOSITE MATERIAL Composites are defined
24、as material systems consisting of two or more constituents, each of which is distinguish- able at a macroscopic level. The constituents retain their individual identities in the composite and are separated by a detectable interface. Generally, one of the constituents acts as a reinforcing agent, and
25、 the. other serves as the matrix or binder. The properties of the composite material are derived from the combina- tion of the properties contributed by the constituents but modified by their synergistic effects. The composite materials of interest in this handbook will be limited to polymeric matri
26、x materials with “ad- vanced” high-modulus or high-performance reinforce- ments. The reinforcements will include fiberglass, graph- ite, and aramid fibers in continuous or discontinuous forms. Boron filament, due to its limited use, will not be discussed. The type of composite structures con- sidere
27、d will include solid laminates and sandwich con- structions. A solid laminate is a product made by bonding together two or more layers of material. The layers may be oriented in various configurations with respect to the orientation of the fibers in order to obtain the most desirable properties. Thi
28、s will be discussed in further detail in par. 1-3.2. l. A sandwich structure is made up of two outer skins of composite laminate or other material, such as metal or wood. These skins are bonded to an internal struc- tural material, such as honeycomb, foam, or, more recently, other configurations suc
29、h as waveformed com- posites (Ref. 1) or tubular structures bonded together in a form similar to honeycomb. Sandwich structures will be discussed in more detail in par. 1-3.2.2. 1-1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1-3.1,l Reinforcemen
30、ts 1-3.1.1.1 Glass Fibers In the United States fiberglass generally implies either E-glass (a lime-alumina-borosilicate glass) or S-glass (a silica-alumina-magnesia glass) fiber and is produced as a continuous monofilament bundle by drawing molten glass through 8 multihole bushing. The size of the h
31、oles wili determine the diameter of the fiber. The mono- filament bundles can then be prepared in different forms such as rovings, multifilament strands, and woven and nonwoven fabrics, A detailed discussion of these materials is given in Ref. 2, and there are numerous reports in the literature on f
32、iberglass. Specific sources are the annual conferences of the Society of the Plastics Industry (SPI), the Society for the Advancement of Materials and Process Engineering (SAMPE), as well as Refs. 3 and 4. 13.1,1.2 Graphite Fibers Most military and aerospace applications requiring high-performance g
33、raphite fibers use fibers produced by the pyrolysis of polyacrylonitrile (PAN) fibers under tension at temperatures of 1760-2760 C (3200-5000F) in a controlled atmosphere. The properties of the fibers are a function of both the tension and the temperature used during pyrolysis. Graphite fibers are u
34、sed in a wide range of applications, some of which include aircraft structural components, satellites, missiles and armament components, X-ray equipment, various auto- motive applications, and sports and recreational equip- ment. More information on graphite fiber can be found in Refs. 2 and 5. 1-3.
35、1.1.3 Aramid Fibers Aramid is a generic term denoting a class of paly- amide materials. The aramid fibers are produced by conventional textile spinning methods. Kevlar aramid fiber and Nomex aramid paper are two materials in this class. Kevlar 49 is the principal aramid fiber currently used in compo
36、site applications. However, recent develop- ments in armor applications are finding a place for Kevlar 29 fibers in composites as well. Aramid fibers are used in composite applications because of their outstanding combination of low density, high strength, and high stiffness. The versatility and dur
37、ability of these fibers, combined with their desirable properties, have design engineers turning to aramid fiber com- posites in many applications requiring light weight, high strength, and durability. The designer should be careful, however, not to use these composites in applica- tions that will e
38、xperience high or sustained compressive loads. Many papers have been published on the use of aramid fibers in composites; specific sources are the conferences and journals of SAMPE and Refs. 6, 7, and 8. 1-3.1.2 Matrix Materials The principal matrix materials used in composites are epoxy, polyester,
39、 and vinyl ester resins. These are fol- lowed by phenolics, polyimides, and silicone resins, which are generally used in specialty applications. -Thermoplastic resin systems, such as polysulfone and polyarylsulfone (Ref. 9), have been used to fabricate high-performance composites. More recently, sys
40、tems such as the bis-maleimides (Ref. IO), phenyladimides, polymerization of monomer reactants (PMR), poly- imides (Refs. 11, 12, and 13), and polyphenyl sulfides (Ref. 14) have been evaluated for fabricating composites with special mechanical and thermal properties. Many other papers have been publ
41、ished on the evaluation of matrix materials for organic composites; specific sources are the conferences and journals of SAMPE and Ref. 2. The polymeric matrix material used in composites has, as its principal role, the responsibility of absorbing and transmitting loads to the reinforcement fiber. H
42、ow- ever, secondarily, the matrix material also controls many other properties, such as the viscoelastic behavior, creep, stress relaxation, and in-plane and interlaminar shear. The chemical, thermal, electrical, and environ- mental aging characteristics (Ref. 15) of the composite are also propertie
43、s that are controlled by the matrix material. The matrix material and the fiber material used to fabricate a composite do not generally play a large part in the selection of the nondestructive testing technique used to inspect the final part. However, the orientation or structural shape may influenc
44、e the interpretation of the results obtained. 1-3.2 CONSTRUCTION 1-3.2.1 Solid Laminates Composite materials are generally used in the form of solid laminates, which may be fabricated in either sheet or molded form and are made by bonding together two or more layers of material. In structural compos
45、ites the materials bonded together to form the composite consist of fibers of reinforcement, as described in par. 1-3.1 .l. These fibers may be oriented in various configurations and may vary in size and shape. Among the various forms of fibers used to fabricate solid laminates are rovings or strand
46、s, chopped fibers, reinforced mats, and woven and nonwoven fabrics. The various forms are explained in detail in Ref, 2. Laminates ar generally formed by use of wet lay-ups or prepregs. The wet lay- up method involves the application of the matrix material to the dry reinforcement at the time of the
47、 buildup of the part to be fabricated. Care must be taken to insure that the reinforcement material is thoroughly wetted out by the matrix material and that no air is entrapped in the composite because this will result in 1 -2 Provided by IHSNot for ResaleNo reproduction or networking permitted with
48、out license from IHS-,-,-voids. Prepregs are preimpregnated combinations of the reinforcement and the matrix materials in a condition ready for fabrication; they are available as woven or nonwoven fabrics, unidirectional tapes, mats, and rovings coated with the various matrix materials. All of the i
49、mportant reinforcing materials, including fiberglass, graphite, and the aramids, can be prepreged. The de- tection of defects in composites by NDT may be affected by the form and makeup of the laminate. 1-3.2.2 Sandwich Construction Sandwich construction consists of two or more lami- nates of different (dissimilar) materials bonded together with an adhesive, as shown in Fig. 1-1. The outermost skins (laminations), made up of solid laminate, furnish the stren
