Crashworthiness, Mechanism and Optimization of Novel Trefoil-like Thin-walled Structures

In recent years, as a key component of lightweight impact-protection devices, thin-walled structure (TWS) with marvelous specific energy absorption (SEA) has attracted wide attention. Inspired by the leaf morphologies of trefoil, this study proposes a kind of novel multi-cell TWS. Its crashworthiness, mechanism and optimization are investigated by combining theoretical analysis, finite element simulation and experiment. The results show that oval-shaped cell exhibits the best crashworthiness compared to sector-shaped and heart-shaped cells. Theoretical analysis indicates that the angular elements related to bifurcation number are the dominant energy-absorbing components. As a result, multi-ribbed trefoil-like TWS demonstrates remarkable crashworthiness, achieving a 106.1% SEA improvement and exceptional crushing force efficiency (CFE) up to 89.2%. Further, increasing the bifurcation number or decreasing the minor axis length of ribbed trefoil-like TWS can reduce transverse spacing between adjacent folds, thereby enhancing crashworthiness by improving load-bearing capacity. After multi-objective optimization, the trefoil-like TWS exhibits a favorable balance between SEA enhancement and peak crushing force (PCF) suppression, while maintaining superior CFE through both vertical and transverse interactions of folds. It outperforms traditional circular and triangular TWSs by 288.1% and 393.9% in SEA, respectively, which provides effective references for the design of high-performing energy-absorbing structures.