Abstract
This study aims at better understanding the damage tolerance of stiffened composite panels subjected to fatigue loads in the post-buckling regime. Ten single-stringer hat-stiffened specimens with an initial delamination between the skin and the stringer foot were manufactured, and then tested under quasi-static and fatigue loads in post-buckling conditions, with different load levels and load ratios. The tests were monitored with digital image correlation and an ultrasonic system, providing data on the displacements, strains, and extension of the delamination length. The quasi-static results showed that the delamination onset, when the initial delamination begins propagating, occurred at loads over twice the buckling load, while collapse occurred for values almost 20% higher than the delamination onset. During fatigue testing at load levels below the delamination onset, the specimens were able to sustain 150000 cycles and then, when tested statically after fatigue, the average load at collapse was reduced by less than 10% with respect to the quasi-static benchmark. When the maximum load during fatigue was increased to 5% over the delamination onset load, the specimens still withstood between 8000 and 16500 cycles before collapse, depending on the load ratio. It was also seen that for tests at the same load level, the specimens with high load ratio had a slower damage propagation.
Original language | English |
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Article number | 110606 |
Number of pages | 14 |
Journal | Composites Part B: Engineering |
Volume | 255 |
DOIs | |
Publication status | Published - 2023 |
Funding
This work was sponsored by the United States Office of Naval Research ( ONR ), under grant award number N62909-17-1-2129 . The views and conclusions contained herein are those of the authors only and should not be interpreted as representing those of ONR, the U.S. Navy or the U.S. Government.Keywords
- Composite structures
- Delamination
- Experimental tests
- Fatigue
- Load ratio
- Post-buckling