Effect of Geometric Parameters on the Failure Index of Composite Deployable Booms

This study investigates how geometric parameters (particularly the length) influence the failure index of thin-walled composite deployable booms. The analysis is performed using a 1D refined finite-element model based on the Finite Element Method (FEM) and the Carrera Unified Formulation (CUF). In this model, the 3D displacement field is expanded across the cross-section with quadratic Lagrange polynomials (L9) and along the boom axis with cubic (B4) finite elements. Hashin’s failure criteria are used at each equilibrium state to compute Failure Index (FI), assuming a pristine linear elastic material. Numerical results show that longer booms achieve larger tip rotations before activating FI, and that the first failure mode is consistently matrix compression (MC). The findings confirm that increasing boom length significantly alters the moment–rotation response, maximum achievable rotation, and damage initiation pattern, underlining the critical role of geometry. A progressive damage model is recommended for future work to capture post-initiation behavior.