What is the advantage of a radius fillet at the base of a stringer?

A radius fillet at the base of a stringer is beneficial because it enhances the structural efficiency of the stiffener within the local panel area. The rounded shape of the fillet helps to distribute stress more evenly along the joint where the stringer meets the panel. This improved stress distribution reduces the likelihood of stress concentrations that can lead to cracking or failure in the composite material.

Additionally, the fillet shape provides a smoother transition between surfaces, which can increase the overall stiffness and strength of the assembly. In composite structures, where the performance under load is critical, ensuring that the stiffeners effectively support the panels without creating weaknesses is key to maintaining structural integrity. Therefore, the radius fillet not only contributes to a more effective load-bearing capability but also assists in maintaining the longevity of the composite assembly by minimizing points of weakness.