A comparative study on thin-walled structures with functionally graded thickness (FGT) and tapered tubes withstanding oblique impact loading

• Obtained an analytical relationship of geometric parameters FGT, SUT, TUT tubes under the same weight.
• Numerical simulations of FGT, SUT and TUT tubes under oblique impact loading.
• Compare the crashworthiness of FGT, SUT and TUT tubes under different loading angles.
• Investigate the critical load angle withstanding the global buckling for the FGT tubes.
• Reveal the crashworthiness of FGT tube is superior to the SUT and TUT tubes under oblique impact.

As a relatively new component with a higher efficiency of material utilization, functionally graded thickness (FGT) structure with probably varying wall thickness becomes fairly promising. This paper compares the energy absorption capabilities of FGT, tapered uniform thickness (TUT) and widely-utilized straight uniform thickness (SUT) tubes subjected to oblique impact loading. The analytical formula is derived for the geometric relationships of these three different configurations (FGT, SUT and TUT) with the same weight. Based on the validated finite element (FE) models, a series of crushing analyses are performed to quantify the specific energy absorption (SEA) of different tubes under axial (0°) and oblique impact loading by varying the loading angles (10°, 20°, 30°). The FGT tubes demonstrate to be more preferable to the others as an energy absorber attributable to their higher capacity of withstanding the oblique loads. Then, crushing analyses of FGT tubes with different gradient exponents are performed to quantify specific energy absorption (SEA) and maximum crashing force. The critical loading angle at which the global buckling occurs is identified for the FGT tubes, and it is found that the energy absorption capacity of FGT tubes, especially with gradient exponent 2.0, was well maintained as the impacting angle increases. The results obtained from this study provide some insights into the design of FGT tube as a potential energy absorber where oblique impact loading is inevitable.