1、r MIL-HDBK-733 ND m 7777770 0038600 7 “ ! a l e 2 F- 2 8- 3 0 MIL-HDBK-733 27 JUNE 1986 MILITARY STANDARDIZATION HANDBOOK NONDESTRUCTIVE TESTING METHODS OF COMPOSITE MATERIALS - RADIOGRAPHY NO DELIVERABLE DATA REQUIRED BY THIS DOCUMENT I . THIS DOCUMENT CONTAINS PAGES AMSC NIA Approved for public re
2、lease; distribution unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-DEPARTMENT OF DEFENSE WASHINGTON, D.C. 20301 NIL-HDBK-733 141LITARY HANDBOOK FOR NONDESTRUCTIVE TESTING METHODS OF COMPOSITE MATERIALS - RADIOGRAPHY 1. This standardizatio
3、n handbook was developed by the Department of Defense with the assistance of the Amy Materials Technology Laboratory, and Dr. Frank P. Alberti of the University of Lowell, Lowell, Massachusetts, in accordance with established-procedure. It is approved for use by all Department.and Agencies of the De
4、partment of Defense. 3 i 2. It is the intent to review this handbook periodically to insure its completeness and currency. Users of this document are encouraged to report any errors discovered and any recommendations for changes or inclusions to Army Materials Technology Laboratory, ATTN: SLCNT-MSR-
5、ES, Arsenal Street, Watertown, MA 02172-2719. ii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-_ MIL-HDBK-733 ND E 7777770 0038602 2 W MIL-HDBK-733 FOREWORD Radiography, A State-of-The-Art-Review Ultrasonics, A State-of-The-Art-Review Acoustic Emis
6、sion, A State-of-The-Art-Review Thermography, A State-of-The-Art-Review 2. Each chapter will be coordinated separately as the amount of materials to review at one time is large. After acceptance of the individual chapters as smaller handbooks, they will be incorporated into a single volume. 3. It is
7、 intended that this volume serve as a reference in which answers may be found to the more.genera1 questions concerning the technical aspects and applications of radiography to composites. iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TABLE OF C
8、ONTENTS (Continued) Scope General . Reference docuTnents . Government documents Other docuTnents . Definitions . Composite material investigations . Introduction Effect of scattered radiation on composites . Penetrmeters for composite materials Other penetrameter approaches . Types of defects Sampli
9、ng for an early study . Operating parameters Classification of composite defects . Type 1 defects Type 2 defects Type 3 defects.? Detection of discontinuities Detection of fiber fraction and orientation . Fiber failure of boron-epoxy laminates Technique . Identification of fiber breakage and matrix
10、cracking Examination of fiber damage . Performance of various classes of resin in carbon fiber Enhancement of small voids Examination of channel network pores Results . Conclusions . Microradiography General . Tech.que . Effects of low voltage radiation Effects of x-ray tube window Radiation attenua
11、tion below 20 KV . Measurement of fatigue damage in boron-epoxy composite laminates Type of analysis Operating parameters Relationship between damaged areas and intense heat . Development of damage . Analysis of effects of the stress state onefatigue behavior . Benefits of contact microradiography o
12、ver microphotography . Estimation of orientation of fibers to plane of the cut . composites . Page iii 1. 1 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 4 5 5 5 5 5 6 6 6. 6 6 6 6 7 7 7 8 8 9 10 10 10 10 10 10 iv Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Se
13、ction Page 4.11 Automatic computer-based radiographic image enhancement . 11 General 11 Electronic enhancement . 11 Electronic enhancement vs optical examination 11 Identification of artifacts 11 Value of video system 11 Further study in flaw detection 11 Improvement in interpretation and evaluation
14、 of data . 12 Signal processing techniques . 12 Method of automatic analysis . 12 Removal of unwanted features . 14 Thresholded image 14 Automatic analysis of film . 16 Enhanced images in carbon-fiber-reinforced epoxy Pressure vessel study 16 composite . 16 Ultrasonic C-Scan vs electronic image 16 A
15、dvantage of digital image analysis . 16 Another study - film image vs visual fluoroscopy 17 Conclusions of another study . 17 Results of study 17 Further study 17 Stereoradiography 17 Determination of depth of a defect . 17 Description of method - no depth perception . 17 Description of method - dep
16、th measurement 18 Results . 18 Opaque additives and image enhancement . 19 General 19 Difficulties of graphite examination . 19 Impregnation procedure . 19 Results 19 Graphite-epoxy composite investigation . 20 Experimental results . 20 Addition of TBE to slits in the specimen . 21 Study of the fail
17、ure mechanism . 22 Effect of TBE-enhanced inspection on fatigue life . 22 Effect of DIB on compression fatigue life 22 Comparisons of damage indications 22 Recommendations 22 Radiographic stereo-mode image. enhancement . 23 Technique 23 Results 23 Another image enhancement investigation 23 Use of bo
18、ron marker fi bers 24 Assessing internal features 24 Radiographic studies . 24 Types of discontinuites found with radiography . 24 Testing composite plate with boron fiber additions . 23 V D 7777770 0038bOLi b . MIL-HDBK-733 TABLE OF CONTENTS (Continued) Provided by IHSNot for ResaleNo reproduction
19、or networking permitted without license from IHS-,-,-MIL-HDBK-733 TABLE OF CONTENTS (Continued) Section Page 4.13.10.3 Types of discontinuities not found with radiog.raphy 24 4.13.10.4 Radiography using new techniques . 24 4.13.10.5 Use of tracer filaments 25 4.13.10.6 Establishing fiber orientation
20、 . 25 5-0 Neutron radiography 25 5.1 General 25 5.2 Use of converter foils . 25 5.3 Sources of neutrons . 25 5.4 Use of neutron radiography . 26 504.1 Other uses . 26 504.2 Checking structural integrity 26 5.5 Use of image enhancement additives . 27 505.1 505.2 5.6 5.6.1 5.6.2 5-6-3 5.7 5.7.1 5.792
21、5-8 5.8.1 5.8.2 Method . Results Study of penetrating radiation techniques Samples Comparison between doped and undoped samples . Results Feasibility of measuring resin content . Samples Results Inspection of fiberglass composites Method . Results 27 27 28 28 28 28 28 28 28 29 29 29 6.0 Notes . 29 6
22、.1 Conversion factors . 29 6.2 Subject term (key word) listing 29 Vi 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-733 1.0 SCOPE 1.1 General This document is intended to provide information on radiographic techniques for examining discon
23、tinuities found in maw types of reinforced composites. The handbook contains varied information from the detection of discontinuities by enhancement methods to the various techniques used such as microradiography, stereoradiography and neutron radiography. The fundamentals of radiography are not inc
24、luded as this type of information is available in MIL-HDBK-728/5. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-733 ND I 7997970 0038607 II m . MIL-HDBK-733 2.0 REFERENCED DOCUMENTS 2.1 Government documents. 2.1.1 Specifications, standards
25、, and handbooks. Unless otherwise specified, the following specifications, standards, and handbooks of the issue listed in the issue of the Department of Defense Index of Specifications and Standards (DoDISS) specified in the solicitation form a part of this standard to the extent specified herein.
26、c Handbook MIL-HDBK-728 Nondestructive Testing 2.2 Other publications. The following documents form a part of this standard to the extent specified herein. The issues of the documents which are indicated as DoD adopted shall be the issue listed in the issue of the DoDISS specified in the solicitatio
27、n. The issues of documents which have not been adopted shall be those in effect on the date of the cited DoDISS. 2.2.1 Technical articles referenced in this handbook are listed at the end of this handbook. (Nongovernment standards are generally available for reference from libraries. They are also d
28、istributed among technical groups and using Federal agencies . ) 3.0 DEFINITIONS O None. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-733 4.0 COMPOSITE MATERIAL INVESTIGATIONS 4.1 Introduction. This handbook is the compilation of the expe
29、riences of many research persons. References included in the handbook are cited so that the individual can obtain more specific information on the particular subject of interest. The handbook will be updated as more users contribute their wo rks . 4.2 Effect of scattered radiation on composites. In
30、the radiography of composites, which are comprised of low and medium density materials, scattered radiation forms a high percentage of the total radiation reaching the film. radiograph these materials, which is inherently less penetrating and more subject to scatter. However, if higher, more penetra
31、ting voltages were used, excessive overall film density could occur, resulting in reduced contrast and a radiograph unreadabie in terms of flaw detection. Scatter is, therefore, a major problem when radiographing composites. In general this presents a paradox for the radiographer since low voltages
32、are desirable for improving subject contrast, but lead to fogging of the image due to scatter, which, in turn, reduces subject contrast. - This is due to the nature of the soft, low voltage radiation used to 4.3 Penetrameters for composite materials. Concerning the use of penetrameters to measure th
33、e sensitivity of a composite material radiographic investigation, the question, of what type of penetrameter design or material should be used is difficult to answer; at this time, specifications are non-existent for adequate penetrameter measurement requirements for composite materials. There are a
34、 number of possible approaches to this problem. material representative of the particular composite specimen. However, at best this would yield only a rough measurement, because of the complex composition of most composite materials. In addition, the design of an adequate penetrameter is very diffic
35、ult because of the many types of imperfections associated with composite specimens (fiber misalignment, fiber breaks, resin content irregularities, fiber matrix unbonds, damage considerations, moisture effects, etc. ). Penetrameters similar in design to those presently used could be made from a 4.4
36、Other penetrameter approaches. Another approach might be to incorporate simulated defects into the penetrameter. For example, in the inspection of a fiber-reinforced composite, a single ply of defective composite could be used as a comparative quality standard when radiographed together with the spe
37、cimen. In any case, the selection of a penetrameter range for which a radiograph may be properly read is also specified.in reference to penetrameters. One penetrameter can be used for each area of the specimen where the density of the radiographic image does not vary more than + 30% or - 15% from th
38、e density of the image of the penetrameter. To cover an entire radiograph of widely divergent density, two penetrameters must be used, one placed at the highest density region and the other at the lowest. This requirement was included in the specifications in order to control the density of radiogra
39、phs, since density plays such an important part in sensitivity, contrast and defect detection ability. 4.5 Types of defects. By far the most widely used radiographic technique for the inspection of composite materials is the straightforward radiographic method. It has been shown that the density on
40、a radiograph depends upon the relative absorption of radiation by the material or defects in its path. In composite material investigations, the radiographer has had to deal with a vast spectrum of reinforcement and matrix material systems, together with a 3 1- Provided by IHSNot for ResaleNo reprod
41、uction or networking permitted without license from IHS-,-,-L MIL-HDBK-733 ND m 7777770 0038607 5 m 1 MIL-HDBK-733 number of associated types of defects. In particular, some of the defect considerations investigated with radiography include: bond evaluations, curing effects, damage considerations, f
42、law content and growth, voids, failure mechanisms, fatigue behavior, fiber characteristics and fiber breaks, fracture characteristics, moisture effects, physical properties; resin content, and thermal effects. The need for detection of these types of defects and the general nature of composite syste
43、ms has brought about a number of advancements in the traditional, straightforward radiographic technique, and has spurred the development of some new and promising techniques. 4.6 Sampling for an early study. In an early composite investigation, Owston and Connorl rePorted the initial results of an
44、extended research program to determine the defects which initiate mechanical failure in carbon fiber-reinforced plastics, and to find nondestructive evaluation (NDE) methods of locating these defects. Approximately 40 specimens, some short rectangular bars, others cylindrical rings, were investigate
45、d. The rectangular bars were 1.5 in. x 0.75 in. x 0.08 in. thick, unidirectional with fibers running lengthwise, and were made by stacking carbon fiber-epoxy prepreg tapes. The cylindrical rings were 4.25-in. inside diameter by 0.1-in. wall thickness, and were an attempt to produce a tensile stress
46、in unidirectional material without the complication of grips. 4.6.1 Operating parameters. Good quality radiographs were obtained at 12 kV using a beryllium window x-ray tube, Kodak Microtex-double-sided industrial film, and a source-to-film distance of 24 inches. Black industrial polyethylene was us
47、ed as a film cassette in some cases, while other exposures were made without a cassette but with all the equipment enclosed in a dark room. Similar results were achieved in both cases. For the ring specimen, a strip of film backed with a thick strip of lead was fitted inside the ring, and the entire
48、 assembly was rotated in front of a collimated beam from the x-ray generator. The resulting radiographs revealed porosity in the specimens, but could not resolve the fibers, their orientation, or denstty. 4.6.2 Classification of composite defects. Composite defects are classified into three groups,
49、Type 1, Type 2 and Type 3. 4.6.2.1 Type 1 defects. Type 1 defects: Those of large proportions affecting wide areas or even the whole of a component, e.g., omission of a layer of prepreg in the layup of a component, faulty resin curing, incorrect compaction due to failure to close the mold correctly. 4.6.2.2 Type 2 defects. Type 2 defects: Smaller scale defects which are still the result of m
