ASTM E1556-20

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1556 − 12 E1556 − 20
Standard Specification for
Epoxy Resin System for Composite Skin, Honeycomb
Sandwich Panel Repair
This standard is issued under the fixed designation E1556; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This specification covers the requirements for an epoxy resin system intended for the repair of sandwich panels for durable,
rigidwall, relocatable structures. It must be usable in a field environment and shall not require the use of special equipment such
as autoclaves or presses. The epoxy system covered by this specification shall be usable for simultaneous impregnation of a
wet-layup composite skin and bonding of that skin to a substrate honeycomb core. The material shall withstand exposure to
temperatures from −54−54 °C to 93°C (−6593 °C (−65 °F to 199°F)199 °F) and high relative humidity, and also the combination
of stress, temperature, and relative humidity that are expected to be encountered in service.
1.2 The values stated in SI units are to be regarded as standard where only SI units are given or where SI units are given first
followed by inch-pound units; where inch-pound units are given first followed by SI units, the inch-pound units are to be regarded
as the standard.
1.3 The following safety hazards caveat refers only to the test methods described in this specification. This standard does not
purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to
establish appropriate safety safety, health, and healthenvironmental practices and determine the applicability of regulatory
limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C297/C297M Test Method for Flatwise Tensile Strength of Sandwich Constructions
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D2344/D2344M Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
D2734 Test Methods for Void Content of Reinforced Plastics
D3165 Test Method for Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated
Assemblies
This specification is under the jurisdiction of ASTM Committee E06 on Performance of Buildings and is the direct responsibility of Subcommittee E06.53 on Materials
and Processes for Durable Rigidwall Relocatable Structures.
Current edition approved Nov. 1, 2012Sept. 1, 2020. Published December 2012October 2020. Originally approved in 1993. Last previous edition approved in 20082012
as E1556 – 08.E1556 – 12. DOI: 10.1520/E1556-12.10.1520/E1556-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E631 Terminology of Building Constructions
E1091 Specification for Nonmetallic Honeycomb Core for Use in Shelter Panels
E1749 Terminology Relating to Rigid Wall Relocatable Shelters
2.2 Military Specifications:Specification:
MIL-I-24768 Insulation, Plastic, Laminated, Thermosetting, Glass-Cloth, Epoxy-Resin
2.3 Military Standards:
MIL-STD-129 Military Marking for Shipping and Storage
MIL-STD-1916 DOD Preferred Methods for Acceptance of Product
2.4 Commercial Standards:Standard:
SAE-AMS-C-9084 Cloth, Glass, Finished for Epoxy Resin Laminates
3. Terminology
3.1 Definitions—See Terminologies —For definitions of general terms related to building construction used in this specification,
refer to Terminology E631, and E1749 for definitions of general terms used in this specification.for general terms related to rigid
wall relocatable shelters, refer to Terminology E1749.
4. Physical Requirements
4.1 Working Characteristics:
4.1.1 Application—The components of the epoxy resin shall be readily hand-mixed to a smooth consistency suitable for
application. It shall be uniform and free of lumps. The resin components, once mixed, shall not settle out. The epoxy material shall
be suitable for the wet-layup impregnation of SAE-AMS-C-9084 glass cloth and for application to core materials over the
temperature range of 1616 °C to 38°C (6038 °C (60 °F to 100°F)100 °F) and at relative humidities of 30 to 75 %.
4.1.2 Application Life—The application life of a 200-g 200 g kit of the mixed epoxy system shall be at least 60 min when tested
in accordance with 4.1.5. The epoxy shall be considered to have reached the end of its application life when the viscosity of this
200-g 200 g quantity of mixed adhesive exceeds 20 000 centipoise.
4.1.3 Curing—The epoxy system shall be capable of curing at 2323 °C 6 2°C (732 °C (73 °F 6 4°F)4 °F) in 7 days, or for no
longer than 3 h at a temperature of 6060 °C to 66°C (14066 °C (140 °F to 151°F),151 °F), with a curing pressure not to exceed
14 psig. In a 23°6 3°C 23 °C 6 3 °C cure, the curing pressure is not required to be maintained after the first 24 h. In a 2323 °C
6 2°C2 °C cure, the epoxy material shall develop the property levels listed in Table 1 within the first 24 h 24 h of cure (see 8.3.5).
In order to meet the requirements of this specification, the property levels listed in Tables 2-4 must be achieved with the 7-day
cure at 2323 °C 6 2°C (732 °C (73 °F 6 4°F).4 °F).
4.1.4 Storage Life—The storage life period of the two parts of the epoxy resin system, when stored in airtight containers at 23°C
(73°F),23 °C (73 °F), shall be at least 12 months from the date of shipment when tested in accordance with 8.3.5.
TABLE 1 Property Requirements for 24-h, 23°C Cure
A
Number of Average Must Exceed Minimum Must Exceed,
Property Test Condition
Specimens MPa (psi) MPa (psi)
Tensile Lap Shear Strength in accordance 23°C (73°F), dry 5 6.9 (1000) 5.85 (850)
with 8.2.1, 8.3.1
Apparent Horizontal Shear Strength in 23°C (73°F), dry 5 15.5 (2250) 13.15 (1910)
accordance with 8.2.2, 8.3.2
TABLE 1 Property Requirements for 24 h, 23 °C Cure
A
Number of Average Must Exceed Minimum Must Exceed,
Property Test Condition
Specimens MPa (psi) MPa (psi)
Tensile Lap Shear Strength in accordance 23 °C (73 °F), dry 5 6.9 (1000) 5.85 (850)
with 8.2.1, 8.3.1
Apparent Horizontal Shear Strength in 23 °C (73 °F), dry 5 15.5 (2250) 13.15 (1910)
accordance with 8.2.2, 8.3.2
A
All specimens tested must exceed these minimum values.
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, DLA Document Services, Building 4/D, 700 Robbins Ave., Philadelphia, PA
19111-5098, http://www.dodssp.daps.mil.19111, http://quicksearch.dla.mil.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
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TABLE 2 Tensile Lap Shear Strength Requirements (See 8.3.1)
A
Number of Average Must Exceed Minimum Must Exceed,
Test Condition
Specimens
MPa (psi) MPa (psi)
−40°C (−40°F), dry 5 13.8 (2000) 11.7 (1700)
23°C (73°F), dry 5 13.8 (2000) 11.7 (1700)
B
93°C (200°F), wet 5 6.9 (1000) 5.9 (850)
TABLE 2 Tensile Lap Shear Strength Requirements (See 8.3.1)
A
Number of Average Must Exceed Minimum Must Exceed,
Test Condition
Specimens MPa (psi) MPa (psi)
−40 °C (−40 °F), dry 5 13.8 (2000) 11.7 (1700)
23 °C (73 °F), dry 5 13.8 (2000) 11.7 (1700)
B
93 °C (200 °F), wet 5 6.9 (1000) 5.9 (850)
A
All specimens tested must exceed these minimum values.
B
Wet = tested immediately after 30 days’ exposure to 60°C (140°F)60 °C (140 °F) and 95 to 100 % R.H.
TABLE 3 Apparent Horizontal Shear Strength Requirements
A
Average Must Exceed Minimum Must Exceed,
Number of
Test Condition
Specimens MPa (psi) MPa (psi)
23°C (73°F), dry 5 31.0 (4500) 26.3 (3820)
B
93°C (200°F), wet 5 13.8 (2000) 11.7 (1700)
TABLE 3 Apparent Horizontal Shear Strength Requirements
A
Number of Average Must Exceed Minimum Must Exceed,
Test Condition
Specimens MPa (psi) MPa (psi)
23 °C (73 °F), dry 5 31.0 (4500) 26.3 (3820)
B
93 °C (200 °F), wet 5 13.8 (2000) 11.7 (1700)
A
All specimens tested must exceed these minimum values.
B
Wet = tested immediately after 30 days exposure to 60°C (140°F)60 °C (140 °F) and 95 to 100 % R.H.
TABLE 4 Flatwise Tensile Strength Requirements
A
Number of Average Must Exceed Minimum Must Exceed,
Test Condition
Specimens MPa (psi) MPa (psi)
−40°C (−40°F), dry 5 2.8 (406) 2.4 (345)
23°C (73°F), dry 5 2.8 (406) 2.4 (345)
B
80°C (176°F), wet 5 1.38 (200) 1.17 (170)
TABLE 4 Flatwise Tensile Strength Requirements
A
Number of Average Must Exceed Minimum Must Exceed,
Test Condition
Specimens MPa (psi) MPa (psi)
−40 °C (−40 °F), dry 5 2.8 (406) 2.4 (345)
23 °C (73 °F), dry 5 2.8 (406) 2.4 (345)
B
80 °C (176 °F), wet 5 1.38 (200) 1.17 (170)
A
All specimens tested must exceed these minimum values.
B
Wet = tested immediately after 30 days exposure to 60°C (140°F)60 °C (140 °F) and 95 to 100 % R.H.
4.1.5 Viscosity—The viscosity of a 200-g 200 g kit of the mixed resin system shall be determined at 2323 °C 6 2°C (732 °C (73 °F
6 4°F)4 °F) using a Brookfield viscometer with a No. 3 spindle at 20 rpm. 20 rpm. A viscosity curve shall be determined by taking
a reading immediately after mixing, and every 5 min thereafter until the viscosity exceeds 20 000 centipoise. The viscosity
immediately after mixing shall not exceed 14 000 centipoise.
4.2 Mechanical Properties—Mechanical properties of test specimens prepared and tested as specified in Section 8 shall meet the
respective requirements listed in Tables 2-4.
4.3 Instruction Sheet—The manufacturer shall provide a dated, coded, and titled instruction sheet outlining instructions for use of
the epoxy system in impregnating and bonding SAE-AMS-C-9084 glass composite skins to honeycomb cores (Specification
E1091, Types I or II). These instructions shall be supplied by the manufacturer with the test report when requesting qualification
(see 7.3) and also with each shipment of epoxy material (see 10.2). The following information shall be included:
4.3.1 All of the information listed in 6.3.1 – 6.3.11.
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4.3.2 The application life of the mixed epoxy system at 2323 °C 6 2°C (732 °C (73 °F 6 4°F)4 °F) and 3838 °C 6 2°C (1002 °C
(100 °F 6 4°F).4 °F).
4.3.3 Mixing instructions shall be stated in detail for the epoxy resin system in the particular container supplied.
4.3.4 Application, impregnating, and curing instructions, including the spreading method, thickness range, and temperature/
relative humidity working limitations.
4.3.5 Material Safety Data Sheets and necessary safety precautions to be observed throughout all operations.
4.3.6 Any other pertinent information relative to the use and storage of the two-part system (resin and curing agent) package (see
10.2).
5. Significance and Use
5.1 Epoxy resin systems used in the repair of composite skin sandwich panels for durable, rigidwall, relocatable shelters must have
a combination of mechanical property levels and environmental resistance that will assure long-term durability of the skins and
the skin-to-core adhesive bonds when exposed to severe climatic exposures. In addition, these epoxy materials must have
processability characteristics that permit their use in a variety of repair scenarios and environments.
5.2 Intended Use—Epoxy systems conforming to this specification are intended for use in the repair of honeycomb panels at the
maintenance field level. The material is intended for use with SAE-AMS-C-9084 glass cloth.
5.2.1 This is a procurement control document for the procurement of the epoxy system and designers shall be aware that the test
values specified herein are based upon tests performed with specific glass-resin composite adherends and shall not be used for
design data.
5.2.2 Epoxy systems covered by this specification are not intended for use in production bonding of sandwich construction.
6. Material and Ordering Information
6.1 General Description—The material shall be a two-part thermosetting epoxy system containing no asbestos, which shall not
have a deleterious effect on the components being impregnated and bonded. It shall have physical characteristics that meet the
requirements of Sections 4 and 7.
6.1.1 Formulation Changes—The epoxy material shall be approved only for the formulation that has passed the qualification tests
and shall be used by the fabricator as approved. Any changes by the manufacturer, such as the adding or changing of pigments,
hardeners, or fillers, or changes in the type or method of manufacture, changes in formulation of the basic resin, or any other
changes, shall be cause for designating the adhesive as a new product that shall not be considered approved. The changed epoxy
resin system shall be given a new code number and shall be resubmitted for approval under this specification. A new instruction
sheet for this reformulated material shall be submitted by the manufacturer to the qualifying activity for approval (see 4.3 and
11.2.2.3).
6.1.2 Identification of Product—The manufacturer shall identify each epoxy resin system submitted under this specification
according to the type of container furnished for it (see Section 10). In addition, the manufacturer shall designate each epoxy system
by a trade name and code number that shall be used to identify it.
6.2 Qualification—In the case of epoxy systems for which the purchaser requires qualification, comprehensive testing in
accordance with Section 8 shall be performed and documented in a test report.
6.3 Procurement Documents—Procurement documents shall specify the following:
6.3.1 Title, number, and date of this specification,
6.3.2 Epoxy resin system type and manufacturer’s trade name,
6.3.3 Date of manufacture,
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6.3.4 Manufacturer’s name and address,
6.3.5 Manufacturer’s batch/lot designation,
6.3.6 Contract number,
6.3.7 Date of shipment,
6.3.8 Expiration dates when stored at 2323 °C 6 2°C (732 °C (73 °F 6 4°F),4 °F),
6.3.9 Manufacturer’sManufacturer’s recommended storage temperature,
6.3.10 Quantity required, and
6.3.11 Manufacturer’s certification that the batch and lot meet the requirements of this specification.
7. Quality Assurance Provisions
7.1 Responsibility for Inspection—Unless otherwise specified in the contract or purchase order, the supplier is responsible for the
performance of all inspection requirements as specified herein. Except as otherwise specified in the contract or purchase order, the
supplier is permitted to use any facility suitable for the performance of the inspection requirements specified herein, unless
disapproved by purchaser. The purchaser reserves the right to perform any of the inspections set forth in the specification where
such inspections are required to ensure that supplies and services conform to prescribed requirements.
7.2 Classification of Tests—The inspection and testing of the epoxy system shall be classified as qualification tests (see 7.3) and
quality conformance tests (see 7.4).
7.3 Qualification Tests:
7.3.1 Sampling Instruction:
7.3.1.1 Epoxy Resin System Samples—The manufacturer shall submit two 1-qt 1 qt samples of the base epoxy resin, along with
the necessary curing agent, from a single-numbered production batch of material being presented for qualification. The
manufacturer shall submit two additional 200-g 200 g kits of the two-part system (resin and curing agent) from the same production
batch for storage life tests (8.3.4). These four 200-g 200 g kit epoxy resin samples shall each be from a batch of most recent
production-scale manufacture, and are not required to be from the same batch as that used in preparing the duplicate panels
specified in 7.3.1.3. All samples shall be identified as to:
(1) Name and address of manufacturer,
(2) Manufacturer’s designation (trade name and code number),
(3) Type of epoxy resin,
(4) Batch number,
(5) Date of manufacture,
(6) Date of submittal,
(7) Expiration date, and
(8) Identification of agency submitting the samples.
7.3.1.2 A statement indicating that the products have not been rebranded shall accompany the samples. If rebranded, the names
of the original manufacturers and original designations of the products shall be indicated. All information submitted will be treated
as confidential.
7.3.1.3 Duplicate Panels—The manufacturer shall submit, along with the epoxy material samples called for in 7.3.1.1, a set of
three panels, prepared in accordance with the procedures described in 8.2.1 – 8.2.3, respectively. These three panels shall be
duplicates of those used in the generation of data for the test report (7.3.2). These panels shall be prepared with epoxy resin samples
from the same numbered batch, and shall be code marked the same as the panels from which the data in the test report (7.3.2) were
obtained.
7.3.2 Test Report—A dated and numbered report, certified by notarized affidavit, shall be furnished, giving the results of all
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applicable tests listed in Tables 2-4. The individual specimen and average values for each test shall be reported (see 11.2.2). Each
value reported shall be shown as being for a uniquely numbered specimen, the numbering of which shall be coded in the report
in such a manner as to clearly establish the particular panel from which the specimen was cut and the particular batch of epoxy
resin with which said panel was prepared and the date of preparation. Coded identification of the epoxy resin batch shall include
the respective dates of manufacture and sizes of batch. Dates on which the different tests were performed shall be shown in the
test report. The test report shall also cover all the requirements of 7.3 – 7.3.4. The actual pressure, temperature, and time of curing
used in the preparation of the test panels shall be reported in the test report.
7.3.3 Instruction Sheet—The manufacturer shall submit an instruction sheet attached to the test report in accordance with 4.3.
7.3.4 Tests—The qualification tests shall consist of all the tests of this specification (Section 8) and shall include approval of the
manufacturer instruction sheet. These tests shall be conducted by an organization approved by the procuring agency. Any changes
shall be subject to the approval of that procuring activity.
7.4 Quality Conformance Tests:
7.4.1 Sampling—Two 200-g 200 g kits of epoxy material (see 10.1), taken at random from the production batch submitted for
qualification, shall be tested. One kit shall be used for acceptance tests and the other shall be retained for retest if necessary. The
storage conditions for the retained sample shall not exceed 2323 °C 6 2°C (732 °C (73 °F 6 4°F)4 °F) and samples shall not be
retained beyond the storage life.
7.4.2 Tests—Samples of each submitted lot of epoxy material delivered on contract or purchase order shall be subjected to the
application life test described in 4.1.2. Lots shall be rejected if one or more of the specimens fail to comply with the requirements.
Test reports, in duplicate, shall be furnished for all quality conformance tests and shall be signed by an authorized representative
of the laboratory performing the test and by a designated representative of the procuring agency.
7.5 Periodic Reevaluation—Unless otherwise specified by the purchaser (see 7.1), epoxy material that has not passed the
qualification tests, or that has previously passed the tests but has subsequently been modified in any manner, must be tested against
this specification and shown to meet its requirements.
8. Test Methods
8.1 Test Conditions—Unless otherwise specified in the detailed test method, all specimens shall be conditioned at 2323 °C 6 2°C
(732 °C (73 °F 6 4°F)4 °F) and 50 6 5 % relative humidity for a period of at least 7 days.
8.2 Preparation of Test Panels:
8.2.1 Preparation of Test Panels for Tensile Lap Shear (Table 2)—A total of two panels shall be prepared as follows (see Fig. 1):
8.2.1.1 Place a flat base plate, (labelled B in Fig. 1) 38.138.1 cm by 35.6 cm (15(15 in. by 14 in.) minimum, upon a film of bagging
material that is approximately 10 cm (4 in.) larger than the base plate in each direction (labelled LBF in Fig. 2).
8.2.1.2 Cover the base plate with a sheet of film to act as a release (labelled RF in Fig. 1).
8.2.1.3 Prepare a 27.927.9 cm by 25.4 cm (11(11 in. by 10 in.) piece of 0.317 cm ( ⁄8 in.) thick MIL-I-2476
...