Evaluating Carbon Fibre-Reinforced Polymer Composite Helical Spring Performances Under Various Compression Angles

Abstract

Highlights: What are the main findings? The optimal curing condition for epoxy resin was determined to be 120 °C for 8 h through tensile and three-point bending tests. This curing condition significantly enhances the mechanical performance of the resin matrix and provides a reliable process basis for subsequent composite spring fabrication. Under varying compression angles and loads, the helical direction consistently exhibited the maximum strain, with the highest strain concentrated in the central coil (region 2), indicating this region as the structural weak point most prone to damage. The stiffness of the spring gradually decreases with the increase in compression angle. What are the implications of the main findings? The clarified strain distribution across different regions and directions facilitates the structural optimisation of composite helical springs and helps reduce the risk of mechanical failure. This study fills the research gap regarding the performance of composite springs under multi-angle loading, promoting their potential applications in complex working environments such as automotive suspension. Springs are widely used in industries such as aerospace and automotive. As the demand for emission reduction grows, the research on lightweight spring performance is becoming increasingly important. This study analyses the mechanical performance of triple-layer braided composite helical springs (TCHS) under various loads and compression angles. Firstly, the optimal high-temperature curing condition of the epoxy resin was determined through tensile and three-point bending analysis. Then, TCHS were fabricated based on optimal epoxy curing conditions, and multi-angle compression tests under different loads were carried out. Simultaneously, strain gauges were installed at various positions and orientations on the inner and outer sides of the spring wire to reveal strain patterns during the compression. The test results indicate that stiffness decreases with increasing compression angle. Additionally, the strain in the inner and outer positions in different directions of the same region increased with the rise in compression force and angle, and strains in the helical direction were the largest. Subsequently, strain in the helical direction across different regions further showed that maximum strain occurred in the centre coil (region 2), with inner and outer helical direction strains reaching −5116.89 με and 5700.15 με, respectively, which are 71.3% and 90.4% higher than those in region 1 and 73.2% and 92.9% higher than those in region 3. As the compression load increased, cracks appeared on the outer side of the centre coil. In addition, the crack was perpendicular to the helical direction, further confirming that the highest strain occurred in the helical direction. This study provides an in-depth analysis of the impact of angle-specific loads on TCHS, offering valuable insights for the design and optimisation of composite helical springs and laying a theoretical foundation for their future development.