CAREER: Bio-inspired Manufacturing of High Strength, High Toughness Metal-Graphene Composites

This Faculty Early Career Development (CAREER) grant focuses on research in the manufacturing of bio-inspired metal-graphene composites that have both high strength and high toughness. Due to their light weight and high strength, metal matrix composites are increasingly used in automotive, aerospace, electronics packaging and thermal management applications. Attaining both high strength and high toughness is an essential requirement for many structural applications. However, it is a significant challenge for metal matrix composites to have both. Nature-evolved, damage-tolerant materials such as nacre, bone and wood are both strong and tough because of their hierarchical composite structure. Unlike bone and wood, which have complex microstructures, nacre exhibits superior mechanical properties with a simple composite microstructure. The toughness of nacre is three orders of magnitude higher than that of its main constituent aragonite owing to its hierarchical “brick-and-mortar” microstructure. This project investigates a novel manufacturing technique to engineer nacre- or bio-inspired three-dimensional metal-graphene composites. This research develops computational and experimental capabilities to understand the strengthening and toughening mechanisms in these materials. This project greatly impacts the metal matrix composites industry. The research is complemented by an educational and outreach program involving curriculum development, research training and engaging K-12 students and the general public. The goal of this research is to manufacture next-generation, damage-tolerant metal matrix composites for mission-critical applications. The research plan is to understand the evolution of the “brick-and-mortar” microstructure in three-dimensional metal-graphene composites as a function of manufacturing process parameters. The fabrication of the “brick-and-mortar” structure involves assembling sucrose-coated copper platelets in a three-dimensional structure, converting sucrose into a graphene network by chemical vapor deposition (CVD) and consolidating the assembly by hot pressing into a composite. An objective of this project is to study the strengthening and toughening mechanisms of strain hardening, deformation twinning, crack deflection and crack bridging as functions of the “brick-and-mortar” microstructure, i.e., copper platelet diameter and thickness, and thickness of the continuous graphene film. The fundamental understanding of the strengthening and toughening mechanisms through molecular dynamics simulations and mechanical testing guides the manufacture of nacre-inspired metal-graphene composite structures. The correlation between processing, microstructure and properties establishes the rational design of the metal-matrix manufacturing process. The bio-inspired composite manufacturing technique can be extended to other metal-graphene composites, e.g., using aluminum, magnesium, nickel, titanium, and their alloys as metal matrices. This project allows the PI to advance the knowledge base in computational modeling and metal matrix composites and establishes his long-term career in advanced manufacturing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.