ASTM D8285/D8285M-19
(Practice)Standard Practice for Compressive Properties of Tapered and Stepped Joints of Polymer Matrix Composite Laminates by Sandwich Construction Long Beam Flexure
Standard Practice for Compressive Properties of Tapered and Stepped Joints of Polymer Matrix Composite Laminates by Sandwich Construction Long Beam Flexure
SIGNIFICANCE AND USE
5.1 Flexure tests on flat sandwich panel construction may be conducted to determine facesheet scarf or step joint compressive strength.
5.2 This practice is limited to obtaining the compressive strength of the sandwich panel scarf and step joint facesheets. Due to the curvature of the flexural test specimen when loaded, facesheet compression strength from this test may not be equivalent to the facesheet compression strength of sandwich structures subjected to pure edgewise (in-plane) compression.
5.3 Factors that influence the compressive response and should therefore be reported include the following: materials (laminate facesheet, core, and adhesive); methods of material fabrication; methods of material preparation, including surface preparation prior to bonding, lay-up, specimen facesheet stacking sequence, and overall thickness; core geometry (cell size); core density; adhesive thickness; joint taper ratio or step length; ply overlap length; relative thickness and stiffness of parent and repair laminates; adhesive bond stiffness; specimen preparation; specimen conditioning; environment of testing; specimen alignment; speed of testing; time at temperature; void content; and volume percent reinforcement. Properties, in the test direction, which may be obtained from this practice, include the following:
5.3.1 Ultimate compressive strength (based on the nominal repair material thickness), (Frcu).
5.3.2 Ultimate running load per ply, (Nj).
Note 2: Concentrated forces on beams with thin facesheets and low density cores can produce results that are difficult to interpret, especially close to the failure point. Wider loading blocks and rubber pads may assist in distributing the forces.
Note 3: To ensure that simple sandwich beam theory is valid, a good rule of thumb for the four-point bending test is the support span length divided by the sandwich thickness should be greater than 20 (S/d > 20) with the ratio of repair material facesheet thickness to core...
SCOPE
1.1 This practice covers the procedure for determination of the compressive strength of a tapered or stepped bonded joint of polymer matrix composite materials. It is applicable to secondary bonded or co-bonded laminates with either unidirectional plies or woven fabric reinforcements. The materials to be bonded may be different systems. In the bondline, a separate adhesive material may or may not be used (example: adhesives may be used with a prepreg system or may not be used with a wet lay-up repair system). The range of acceptable test laminates and thicknesses are described in 8.2.7. The standard repair types are the same as for the tensile loading in Practice D8131/D8131M. While external patch repairs are not explicitly covered in this practice, these repairs could be tested as a non-standard specimen using this practice.
1.2 This practice supplements Test Method D7249/D7249M for compressive loading of facesheet sandwich constructions by long beam flexure. Several important test specimen parameters (for example, joint length, ply overlaps, step depth, and taper ratio) are not mandated by this practice; however, these parameters are required to be specified and reported to support repeatable results.
1.3 Unidirectional (0° ply orientation) composites as well as multi-directional composite laminates and fabric composites, can be tested.
1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.4.1 Within the text, the inch-pound units are shown in brackets.
1.5 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 esta...
General Information
Relations
Standards Content (Sample)
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.
Designation: D8285/D8285M − 19
Standard Practice for
Compressive Properties of Tapered and Stepped Joints of
Polymer Matrix Composite Laminates by Sandwich
1
Construction Long Beam Flexure
This standard is issued under the fixed designation D8285/D8285M; 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.
1. Scope 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This practice covers the procedure for determination of
responsibility of the user of this standard to establish appro-
the compressive strength of a tapered or stepped bonded joint
priate safety, health, and environmental practices and deter-
of polymer matrix composite materials. It is applicable to
mine the applicability of regulatory limitations prior to use.
secondary bonded or co-bonded laminates with either unidi-
1.6 This international standard was developed in accor-
rectional plies or woven fabric reinforcements. The materials
dance with internationally recognized principles on standard-
to be bonded may be different systems. In the bondline, a
ization established in the Decision on Principles for the
separate adhesive material may or may not be used (example:
Development of International Standards, Guides and Recom-
adhesives may be used with a prepreg system or may not be
mendations issued by the World Trade Organization Technical
used with a wet lay-up repair system). The range of acceptable
Barriers to Trade (TBT) Committee.
test laminates and thicknesses are described in 8.2.7. The
standard repair types are the same as for the tensile loading in
2. Referenced Documents
Practice D8131/D8131M. While external patch repairs are not
2
2.1 ASTM Standards:
explicitly covered in this practice, these repairs could be tested
D792 Test Methods for Density and Specific Gravity (Rela-
as a non-standard specimen using this practice.
tive Density) of Plastics by Displacement
1.2 This practice supplementsTest Method D7249/D7249M
D883 Terminology Relating to Plastics
for compressive loading of facesheet sandwich constructions
D3171 Test Methods for Constituent Content of Composite
by long beam flexure. Several important test specimen param-
Materials
eters (for example, joint length, ply overlaps, step depth, and
D3878 Terminology for Composite Materials
taper ratio) are not mandated by this practice; however, these
D5229/D5229M TestMethodforMoistureAbsorptionProp-
parameters are required to be specified and reported to support
erties and Equilibrium Conditioning of Polymer Matrix
repeatable results.
Composite Materials
D7249/D7249M Test Method for Facesheet Properties of
1.3 Unidirectional (0° ply orientation) composites as well as
Sandwich Constructions by Long Beam Flexure
multi-directional composite laminates and fabric composites,
D8131/D8131M Practice for Tensile Properties of Tapered
can be tested.
and Stepped Joints of Polymer Matrix Composite Lami-
1.4 Units—The values stated in either SI units or inch-
nates
pound units are to be regarded separately as standard. The
E4 Practices for Force Verification of Testing Machines
values stated in each system are not necessarily exact equiva-
E6 Terminology Relating to Methods of Mechanical Testing
lents; therefore, to ensure conformance with the standard, each
E122 Practice for Calculating Sample Size to Estimate,With
system shall be used independently of the other, and values
Specified Precision, the Average for a Characteristic of a
from the two systems shall not be combined.
Lot or Process
1.4.1 Within the text, the inch-pound units are shown in
E177 Practice for Use of the Terms Precision and Bias in
brackets.
ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
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This practice is under the jurisdiction ofASTM Committee D30 on Composite
2
Materials and is the direct responsibility of Subcommittee D30.09 on Sandwich For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Construction. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Sept. 1, 2019. Published October 2019. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D8285_D8285M-19. the ASTM website.
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