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ASTM D7249/D7249M-20
Standard Test Method for Facesheet Properties of Sandwich Constructions by Long Beam Flexure
NORMA vydaná dňa 1.2.2020
Informácie o norme:
Označenie normy: ASTM D7249/D7249M-20
Dátum vydania normy: 1.2.2020
Kód tovaru: NS-983986
Počet strán: 10
Približná hmotnosť: 30 g (0.07 libier)
Krajina: Americká technická norma
Kategória: Technické normy ASTM
Kategórie - podobné normy:
Anotácia textu normy ASTM D7249/D7249M-20 :
Keywords:
bending stress, facesheet modulus, facesheet strength, facesheet stress, flexural stiffness, sandwich construction, sandwich deflection,, ICS Number Code 79.060.01 (Wood-based panels in general)
Doplňujúce informácie
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5.1 Flexure tests on flat sandwich construction may be conducted to determine the sandwich flexural stiffness, the core shear strength, and shear modulus, or the facesheets’ compressive and tensile strengths. Tests to evaluate core shear strength may also be used to evaluate core-to-facesheet bonds. 5.2 This test method is limited to obtaining the strength and stiffness of the sandwich panel facesheets, and to obtaining load-deflection data for use in calculating sandwich beam flexural and shear stiffness using Practice D7250/D7250M. 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 Core shear strength and shear modulus are best determined in accordance with Test Method C273/C273M provided bare core material is available. Test Method C393/C393M may also be used to determine core shear strength. Practice D7250/D7250M may be used to calculate the flexural and shear stiffness of sandwich beams. 5.4 This test method can be used to produce facesheet strength data for structural design allowables, material specifications, and research and development applications; it may also be used as a quality control test for bonded sandwich panels. 5.5 Factors that influence the facesheet strength and shall therefore be reported include the following: facesheet material, core material, adhesive material, methods of material fabrication, facesheet stacking sequence and overall thickness, core geometry (cell size), core density, adhesive thickness, specimen geometry, specimen preparation, specimen conditioning, environment of testing, specimen alignment, loading procedure, speed of testing, facesheet void content, adhesive void content, and facesheet volume percent reinforcement. Further, facesheet strength may be different between precured/bonded and co-cured facesheets of the same material. 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 pressure 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 (1.1 This test method covers determination
of facesheet properties of flat sandwich constructions subjected to
flexure in such a manner that the applied moments produce curvature
of the sandwich facesheet planes and result in compressive and
tensile forces in the facesheets. Permissible core material forms
include those with continuous bonding surfaces (such as balsa wood
and foams) as well as those with discontinuous bonding surfaces
(such as honeycomb).
1.2 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. 1.2.1 Within the text, the inch-pound units are shown in brackets. 1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Note 1: Alternate procedures for determining the compressive
strength of unidirectional polymer matrix composites materials in a
sandwich beam configuration may be found in Test Method
D5467/D5467M.
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. |
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