A compression after impact (CAI) test is used to measure the residual strength of composite laminates after being damaged by an impact. Such damage can be caused by dropping tools on a laminate or by flying debris. Even if the impact does not result in visible damage, the compressive strength of the composite can be compromised.
The CAI test method and the associated test fixture are outlined in Boeing® Specification BSS 7260. This post-impact compression test is targeted for carbon and aramid fiber reinforced plastic (CFRP) composite laminates. It is widely used to assess the relative performance of composite laminates with different fiber matrix combinations.
Before testing the compressive strength of the composite, we simulated impact damage by applying a specific energy with an instrumented impact tester; alternatively, you could use the manual drop weight approach.
Next, we used a floor model electromechanical universal tester equipped with our Boeing CAI Test Fixture and Bluehill® 2 Software to apply the compressive force. The post-impact test fixture incorporates adjustable side plates to accommodate for both variations in thickness and overall dimension. It is designed to prevent specimen buckling while the specimen is end-loaded to failure.