Fatigue test of lightweight composite wing structure

Fatigue tests of hat-shape stringer stiffened panel are conducted, where this panel is a typical part of upper skin of lightweight composite wing using new production technology of stitching, co-bonding and RTM method. Impact damages are applied on skin/stringer co-bonded part and typical skin part of the test panel by drop-weight impact machine. There are two phases in the present test. The first phase is fatigue tests to verify durability of the structure with barely visible impact damages. The second phase is flaw growth tests for evaluation of visible impact damage growth to estimate inspection intervals. The Mini-TWIST (shortened version of The Transport WIng STandard load program) spectrum loading is used for both tests. Non-destructive inspection is carried out by pulsed thermography during the test to observe damage propagation. Finally, static load is applied up to design limit load to verify the residual strength after all the spectrum loading tests.