Compression Testing of Large Gage Length Composite Coupons

A compression testing procedure for composites is described. Using the procedure large gage length, variable thickness specimens were tested. Buckling and end brooming were prevented by the testing procedure, and either extensometers or strain gages were used to record strain. Specimens were gripped on one end and compressed against a bearing plate on the other, but they can be gripped on both ends. The practicality of the testing procedure is demonstrated using compression test results for two different laminates of a graphite/epoxy composite. Types of failure modes are reviewed. The effects of extensometer attachment are discussed and comparisons made between strain readings using extensometers and strain gages.