Laminated Test Specimen for Thin Metallic Materials - A Novel Approach to Determine Compression Strength

Mechanical property testing is needed to support material procurement and engineering design.  The existing industry standard for static testing of metallic materials in compression is ASTM E9.

Compression testing of thin metallic materials using the standard rectangular (flat) specimen per ASTM E9 is challenging.  Inconsistent test results are possible due to operator variables.  If the specimen buckles prematurely due to inadequate lateral support from the test fixture, test results may be too low; with overly conservative results potentially adding unnecessary structural weight.  On the other hand, if the fixture provides too much lateral restraint due to over-tightening, test results may be too high, with non-conservative results creating potential safety concerns.  The goal in any testing is to eliminate the variability in test data due to the testing itself.

A new specimen configuration is proposed for testing static compression strength of thin gage metallic materials, such as sheet or extrusion.  The laminated test specimen configuration was developed in 1998 by Alcan Aluminum (now Constellium) in France for their internal use.  Alcan gave Boeing permission to perform further investigation into the new test specimen configuration.  To date, Boeing has conducted initial screening tests to evaluate the new specimen configuration, using aluminum and titanium sheet, but additional testing is required to fully validate the concept.

Use of the new configuration may produce more accurate and consistent test results compared to the current method, which could translate into increased design values and lower structural weight.  Once fully characterized, this new configuration could be incorporated into ASTM E9 as the preferred alternative for testing thin materials.