Analysing impact characteristics of composite helical springs with multi-braided layers based on virtual fiber model

Heavy-duty springs can be made lightweight by replacing metallic materials with polymer composite materials. Most existing studies mainly concentrate on the static performance of composite helical springs (CHSs), understanding the dynamic impact of CHSs is limited. In this study, the impact response of CHSs with multi-braided layers (MBLs-CHS) is investigated using drop-weight impact tests. Experimental results indicate a sequential improvement in the impact performance of CHSs with single, double, and triple braided layers (SCHS, DCHS, and TCHS). Specifically, TCHS demonstrates enhancements of up to 5.1 %, 78.3 %, and 34.1 % in deformation resistance, F_max, and E_e, respectively, compared to SCHS. Subsequently, a virtual fiber model (VFM) elucidates the internal mechanism behind this improvement. The force-bearing contribution of the corresponding braided layers in SCHS, DCHS, and TCHS is similar, emphasising that the impact response difference is primarily attributed to the additional braided layer. Additionally, stress and motion responses of VFM revealed non-linear characteristics in stress, displacement, and velocity waves transitioning of MBLs-CHS. Finally, the impact mitigation ability of MBLs-CHS can be calculated based on velocity responses of VFM, highlighting that of TCHS improves by 111.6 % and 42.0 % compared to SCHS and DCHS, respectively. This research establishes a robust foundation for dynamic studies and offers valuable guidelines for the engineering design of CHSs.