Crown-Tulip Trigger Mechanisms to Improve Crashworthiness Design of Composite Tubular Structures

Background: This article presents the design development of a new crown-tulip trigger mechanism to initiate progressive failure and reduce initial collapse load in comparison with the existing trigger designs of bevel and tulip in tubular composite structures. Objectives: Through experimental impact testing, comparisons are drawn to the existing designs, such as the 45° bevel and 4T90° tulip trigger mechanism. Methods: This experimental testing design phase demonstrated a significant improvement in the crush force efficiency of crown-tulip trigger mechanisms compared to the previously established Tulip trigger design (4T90°). The experimental results were utilised to develop equivalent numerical models in LS-DYNA. Results: The validated models were employed for further design development, studying the influence of increased bevel angles (30°, 45°, and 60°), tulip angles (90°, 100°, 120°, 140°, and 160°), crown notch depth, crown notch angle, and number of tulip tips/crown notches on the crashworthiness and force response. Conclusions: This culminated in the numerical design development of the 4T160°-40°-2 mm crown-tulip trigger, which achieved 20% higher specific energy absorption, a 22% increase in crush force efficiency, and a 36% higher mean force compared with the 4T90° Tulip-triggered specimen. The outcomes of this research will be implemented in automotive, aerospace, and defence sub-structures.