On defining core properties for composite sandwich panels
In the interests of performance, fuel economy, as well as other factors, weight reduction in transportation vehicles is receiving considerable attention. It is well know that sandwich construction can provide a structural component that has both high stiffness and high strength per unit weight. In a sandwich structure a low density, low stiffness, low strength core is bonded between two high stiffness, high strength facesheets producing a structure that is particularly efficient in resisting bending loads. A key element in a sandwich construction is the core. Its` properties, particularly its` shear modulus and yield/failure stress, must be accurately known for proper structural design. Two ASTM standards exist for determining these properties; ASTM C273-88 and ASTM C393-94. The ASTM C273-88 is a simple shear test on the core material alone, while the ASTM C393-94 obtains core properties through bending data on sandwich beams. It is well known, particularly for the lower cost cores, e.g. foams, that differences in properties, sometimes appreciable, exist for these two tests. One of the main purposes of the present paper is to show that specimen geometry can have a first order effect on the material properties, i.e. only for ratios of sandwich beam length to thickness in the ASTM C393-94 test greater than 20 do the results of the two ASTM tests approach each other. A second objective of the paper is to determine the effect of the shear test plate thickness in the ASTM C273-88 test. Steel plates of thickness {1/4} inches, 5/8 inches, and 1 inch were used, i.e. bonded to the core specimens and then tested in simple shear. Only for the stiffest cores tested were any statistically different results obtained and then only minor differences for the {1/4} inches plates. Some typical test results through to core yield/failure are shown to demonstrate the different post yield behaviors.
- OSTI ID:
- 577579
- Report Number(s):
- CONF-970431-; TRN: 98:000974-0015
- Resource Relation:
- Conference: United new generation vehicle conference and exposition, Detroit, MI (United States), 7-10 Apr 1997; Other Information: PBD: 1997; Related Information: Is Part Of Advanced composites - proceedings; PB: 639 p.
- Country of Publication:
- United States
- Language:
- English
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