Effects of Nesting Configuration and Foam Fillers on the Axial Crushing of Carbon Fiber Epoxy Composite Tubes

ABSTRACT This study investigates the axial crushing behavior and energy absorption characteristics of nested carbon fiber reinforced polymer (CFRP) tubes, both empty and filled with expanded polypropylene (EPP) foam, under quasi‐static compression loading. The research explores how variations in tube geometry, specifically diameter, length, and nesting configuration affect crashworthiness parameters such as specific energy absorption (SEA), crush force efficiency (CFE), and absorbed energy (AE). Three different nesting arrangements were tested: equal‐length tubes, short‐to‐long, and long‐to‐short configurations. Results showed that equal‐length CFRP tubes exhibited the highest peak force (~76 kN) and absorbed energy (~3683 J), indicating superior load‐carrying capacity and crashworthiness. With the EPP foam added, the energy absorption performance significantly improved, with the highest energy increase (37%) observed in the equal‐length configuration. Foam‐filled structures also showed a more stable deformation pattern, preventing abrupt force drops typically observed in empty tubes. However, although AE values improved, the gains in SEA were more modest, and in some configurations, SEA even slightly decreased, indicating that higher energy absorption does not necessarily translate to greater efficiency. The short‐to‐long arrangement exhibited abrupt force increases due to sequential tube engagement, while the long‐to‐short design showed smoother force transitions but lower overall energy absorption. These findings underscore the influence of geometric arrangement and foam reinforcement on the progressive failure mechanisms and energy absorption potential of CFRP tubes.