Fibre-reinforced composite materials have been used in aerospace and other fields for over sixty years due to their significant lightweight advantages. According to a team from the Institute of Mechanics under the Chinese Academy of Sciences, composite laminates possess anisotropy and designability, and in engineering, a fixed combination of four layup angles has long been used to achieve on-demand design. 

However, the out-of-plane heterogeneity and coupling effects of laminates significantly increase the complexity of design and analysis. To address these issues, the research team, led by Qiu Cheng, in collaboration with scholars from the Hong Kong University of Science and Technology and Stanford University, proposed a method that significantly simplifies the design and fabrication process of laminates.

The research team combined traditional engineering methods with AI to create a tool that helps design layered materials more efficiently. Their results show that using balanced layer patterns can produce very uniform properties through simple repetition. Among these, the “double balanced” pattern is the simplest and works well even with thin materials. The “triple balanced” pattern offers more flexibility, allowing engineers to fine-tune the material’s mechanical properties while still keeping it uniform.

The “DD pattern” shown in the laminate design refers to Double-Double-type architectures, which use simplified stacking sequences to achieve higher stiffness and strength with fewer design variables.

Joints 13% stronger 

Using common structural examples, the study shows that balanced layer designs can make both design and manufacturing simpler. For example, when making V-shaped parts, traditional layered materials tend to warp a lot during the curing process, while double-balanced layers keep this deformation much lower.

Tests on bending also show a difference: in traditional materials, stiffness changes a lot depending on thickness, but in double-balanced layers, bending performance stays stable even when the thickness changes.

Because of this property, it’s easy to design materials with different thicknesses, which helps make structures lighter. For example, in a beam under bending, a variable-thickness design using double-balanced layers can increase stiffness by 26% while keeping the same weight, and it uses the material more efficiently. At the same time, the strength at the joints is about 13% higher than in a traditional design with uniform thickness.

Overall, this research offers methods and theory to design advanced composite materials more efficiently, according to the research team, and it could be very valuable for building the next generation of lightweight aerospace structures. Particularly due to their intensive use of composite materials: for example Govy AirCab, the multi-rotor flying vehicule developed by China’s GAC group, which has just completed its first urban flight over Guangzhou, Guangdong province, is composed of more than 90% carbon fibre composite materials.