Dynamic Axial Crushing Characteristics of Thermoplastic Composite Hierarchical Cylindrical Structure Consisting of Glass-Fiber Reinforced Polypropylene

Thermoplastic lightweight composite structures have attracted much attention in engineering owing to their high toughness, damage tolerance and recyclability. The security and reliability of such structures under pulsed or sustained loading conditions are crucial before engineering applications. In this work, structural responses and energy absorption capacity of thermoplastic composites (continuous woven glass-fiber reinforced polypropylene) formed hierarchical cylindrical structures under sustained dynamic crushing loading conditions were characterized. Results showed good crashworthiness and stabilized global collapse failure mode. Under the low axial crushing speed ([Formula: see text]10[Formula: see text]m/s), the fabricated cylindrical structures introducing hierarchical bending-dominated unit cells achieved lower initial crushing peak load and stabilized following load plateau. During the crushing period, a crushing force efficiency greater than 0.6 is achieved until densification, reaching 0.9 in the middle stage. Moreover, no fragmentations or debris ejections were observed, though severe fracture damage occurred. After being crushed, the residual structural components maintain a whole structure and can rebound to 90% of the initial structural height when unloaded. Theoretical analyses were carried out to estimate the mean crushing force of the hierarchical cylindrical structure. The predicted mean crushing forces for static and dynamic conditions, respectively, corresponding to the observed failure modes, agreed well with the experimental results. This research gives reference significance to the design of dynamic energy absorption of engineering thermoplastic composite structures.