Understanding the static performance of composite helical springs with braided nested structures

Application of composite helical springs (CHSs) is constrained by their poor static compression performance. In this study, a novel composite helical spring with a braided nested structure (BNCHS) is proposed. The fiber volume fraction (V-f) of BNCHS with braided angle of 15 degrees and 30 degrees (BNCHS15 degrees and BNCHS30 degrees) only increases by 0.9% and 1.8% respectively comparing with that of unidirectional composite helical spring with V-f of 55% (UCHS55%). The compression experimental results show that the spring constant of BNCHS15 degrees and BNCHS30 degrees can reach 105.4% and 171.4% higher than that of UCHS55% respectively. The internal mechanism of significantly improving compression performance of BNCHS is revealed by using a meso model. Numerical result shows that the mises stress of BNCHS15 degrees and BNCHS30 degrees can be 2.43 and 3.14 times higher than that of UCHS55% respectively. Finally, the resilience and specific spring stiffness of BNCHS and steel are compared, highlighting the obvious advantage of static performance of BNCHS.