Improving the efficiency of aerospace structures involves reducing their weight and maintaining their safety throughout their life cycle. To avoid oversizing, a deep knowledge of the damage mechanism in composite materials is crucial, and interlaminar fracture, or delamination, is one of the most critical mechanisms. Understanding delamination behavior and characterizing the Interlaminar Fracture Toughness (IFT) of composites is key to designing safe and efficient structures. Standard tests to quantify IFT are restricted to unidirectional (UD) specimens with delamination propagation parallel to the fiber. However, structures are built using Multi-Directional (MD) laminates, where delamination may appear at any interface and propagate in any direction, and IFT may differ from that obtained by standard tests, leading to oversized, inefficient structures. The main problems that prevent IFT test for MD laminates are: elastic couplings, thermal residual stress, finite width effects, and delamination migration. Currently, there is no understanding of whether migration can be reliably avoided in mode I tests, while it can be prevented in mode II and mixed mode I/II tests. Since migration depends on the state of shear stress at the delamination crack tip, our objective is to find a way to design MD specimens for the mode I test that could avoid migration.
Abstract Improving the efficiency of aerospace structures involves reducing their weight and maintaining their safety throughout their life cycle. To avoid oversizing, a deep knowledge [...]
Investigating how to avoid delamination migration in mode I delamination tests with multidirectional specimens 
