The Dynamic Response Of Stringer-stiffened Curved Composite Panels Under The Hail Ice Impact

The structure of the aircraft, which made by carbon fiber composites, are always underattacked by hail ice storm during the flying. It would damage the aircraft and threat to the safetyof passengers. And this behavior could be seen as a typical impact behavior.The dynamic mechanical property of three principal directions of the carbon fibercomposites have been tested by using14mm steel SHPB. By contrast the static and dynamicstress-strain relationship, it could be found that the failure mode of it is brittle fracture when itunder a thickness direction compression. The compressive strength goes up when strain raterising, but the dynamic compressive strain smaller than the static one. The compressive strengthon the in-plane direction is smaller than that on thickness direction. And the relationship betweendynamic compressive strength and strain rateon in-plane direction follows the same rule withthat on thickness direction, but the static compressive strength higher than the dynamic one.From the damage situation, it could be observed that when the composites under dynamiccompressive loading from the in-plane direction, the specimen is damaged by delamination. Onthe other hand, when under static compressive loading from that direction, the specimen isdamaged by the mixture of delamination and shearing failure. And there are three zones existwhen it under static compressing, which have different failure mode.Meanwhile, the dynamic mechanical property of ice has been tested by using37mmaluminum SHPB. The result shows that ice is a strain rates sensitive material as the carbon fibercomposites when it under compressive loading. The slope of the strength vs. strain rises up whenthe strain rate increasing. The failure mode of ice is crush. Furthermore, the function of the pulseshaper has been discussed. And the relationship between the shaping ability and diameter of thepulse shaper and the velocity of the striker bar has been illustrated by theoretical andexperimental analysis.On this basis, experimental and numerical investigation of hail ice impact onstringer-stiffened curved composite panels has been conducted. There are two types of theimpact, which differentiated by the impact location have been researched. When under impact onthe skin at the middle of the bay, the delamination starts at the interface between skin and flangeof the string near by the shear ties due to the constraint of shear ties. Then the delaminationhappens at the interface near the impact location due to the stiffness change on the flange.Otherwise, when under impact on the skin at the middle of flange, the delamination on theinterface starts at a critical velocity at the impact location because the deformation uncoordinatedat the interface caused by the thickness change of the flange.