Enhancing the mechanical performance of composite corners through microstructural optimization and geometrical design

Processing carbon fiber-reinforced composites into corner sections through compression molding poses challenges due to the limited flowability of continuous prepregs, resulting in reduced curved beam strength (CBS). The use of discontinuous plies was explored, including random HexMC and unidirectional chopped strand (CS) prepreg. A first comparison on flat UD or Quasi Iso (QI) plates highlighted the potential interest of CS in terms of stiffness and lower strength penalty as HexMC. The iso-thickness corners produced from HexMC reached a CBS of 1 kN while CS QI had a CBS of 2.5 kN, overperforming corners made from neat prepregs (2.1kN) thanks to the improved flowability of the CS. By selecting an optimized geometry at equivalent mass, the CBS of CS corners further increased to 6.6kN. The performance of composite corners can thus be greatly enhanced by a combination of the material microstructural arrangement and the geometrical design of the mold.