This test method covers the determination of the properties of ﬂat sandwich constructions subjected to ﬂatwise ﬂexure in which the applied moments cause curvature of the sandwich facing planes.
These tests may be conducted to determine the sandwich ﬂexural stiffness, the core shear strength and shear modulus, or the facings compressive and tensile strengths. Tests to evaluate core shear strength may also be used to evaluate core-to-facing bonds.
These testing fixtures follow a standard method of obtaining the sandwich panel ﬂexural strengths and stiffness.
The sandwich stiffness and core shear modulus may be determined by calculations involving measured deﬂections of sandwich ﬂexure specimens. Tests can be conducted on short specimens and on long specimens or on one specimen loaded in two ways, and the ﬂexural stiffness and shear modulus can be determined by simultaneous solution of the complete deﬂection equations for each span or each loading. If the facing modulus values are known, a short span beam can be tested and the calculated bending deﬂection subtracted from the beam’s total deﬂection. This gives the shear deﬂection from which the core shear modulus can be determined.
|Test Standard||ASTM C393, D7249, D7250 and D546|
|Maximum Load||25 kN|
|Temperature Range||da -80 °C a 149 °C|
|Specimen Thickness||1-10 mm|
|Specimen Width||40 mm|
|Specimen Length||700 mm|
This test method it is also useful for flexural testing any other type of specimen, e.g., solid laminates per ASTM D 790, D 6272, and ASTM D 7264. . The standard Long Beam Flexure Fixture can also be customized. ASTM C 393 permits the use of either single loading, or two-point . These are usually termed three-point and four-point flexure, respectively. The fixture can be used in either configuration, one loading head being removed and the remaining one centered on the loading beam to perform three-point loading.
- ASTM Standard C 393-11 (2011), “Flexural Properties of Flat Sandwich Constructions,” American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1957);
- ASTM Standard D 790-10 (2010), “Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials,” American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1970);
- ASTM Standard D 6272-10 (2010), “Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending,” American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 1998).
- ASTM Standard D 7264-07 (2007), “Flexural Properties of Polymer Matrix Composite Materials,” American Society for Testing and Materials, West Conshohocken, Pennsylvania (first issued in 2006).
- ASTM C 273 Test Method for Shear Properties of Sandwich Core Materials;
- ASTM C 480 Test Method for Flexure Creep of Sandwich Constructions;
- ASTM E 4 Practices for Force Verification of Testing Machines.