Significance and Use
5.1 This test method is designed to produce composite stiffener cross-section local buckling and crippling data for research and development, and for structural design and analysis. The standard generic configurations for this procedure provide data for two types of cross-section segments: one-edge-free and no-edge-free. This type of data is used in classical stiffener analysis methods. Compressive loading of composite column type specimens may exhibit one of four modes: (1) a compression material strength failure, (2) an overall column flexural, torsional, and or flexural-torsional instability, (3) a local instability followed by a continued post-buckled force carrying capability which eventually results in a material strength failure, or (4) a combination of local and overall instability followed by post-buckling failure. The first two modes are outside the scope of this test method. The latter two modes are categorized as crippling failure and is the purpose of this test method.
5.1.1 The desired failure mode is characterized by an initial linear elastic structural deformation. Continued loading eventually renders one of the cross-sectional segments unstable. Additional loading beyond this point of initial buckling exhibits a pattern of local lateral deflections or buckles. These deflections will grow, and possibly change modes, until catastrophic column failure occurs. This failure is considered the ultimate crippling stress for the buckled segments.
5.2 General factors that influence the mechanical response of composite laminates and should therefore be reported include the following: material, methods of material preparation and lay-up, specimen stacking sequence, specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, speed of testing, time held at test temperature, void content, and volume percent reinforcement.
Scope
1.1 This test method covers the local buckling and crippling stresses for one-edge-free and no-edge-free cross section configurations using solid laminate composite material construction. Design of test specimens is covered in Guide D8511/D8511M. A number of test parameters may be varied within the scope of the standard, provided that the parameters are fully documented in the test report. The composite material forms are limited to continuous-fiber or discontinuous-fiber (tape, fabric, braids or hybrids of these forms) reinforced composites.
1.2 This test method requires careful specimen design, instrumentation, data measurement and data analysis. The use of this test method requires close coordination between the test requestor and the test lab personnel. Test requestors need to be familiar with Guide D8511/D8511M and CMH-17 Volume 3 Chapter 92 (1).
1.3 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.
1.3.1 Within the text the inch-pound units are shown in brackets.
1.4 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.
1.5 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.
