The cover of the November issue of MRS Bulletin featured work by Dr. Brett Compton, assistant professor in the Department of Mechanical, Aerospace, and Biomedical Engineering (MABE).

The cover depicts a 3D-printed, carbon fiber-reinforced epoxy honeycomb structure from Compton’s postdoctoral work at Harvard University. Most 3D-printed polymers are thermoplastics such as ABS or PLA. Thermoplastic polymers melt at elevated temperature and solidify at room temperature in a reversible fashion, and typical polymer 3D printers function like high-precision hot glue guns.

However, the epoxy that forms this honeycomb structure is a thermoset polymer, which means that it is liquid at room temperature and undergoes an irreversible crosslinking reaction at elevated temperature to cure the material and form a solid part. Thermoset polymers offer a wider range of material properties than thermoplastics, including high temperature performance, chemical resistance, and compatibility with structural and functional fillers. This honeycomb structure is part of the work that first demonstrated 3D-printable fiber-reinforced thermoset composites.

The honeycomb motif is frequently used as the in-fill pattern for components printed using extrusion-based AM technologies (FDM and direct-write). As such, it represents the mesostructure between the macroscopic shape, form, or component that a designer would want to print and the microstructure of the fiber-reinforced feed stock material. By controlling architecture across multiple length scales (fiber orientation, honeycomb density/morphology, and bulk shape), AM technologies and new thermoset feedstocks have the potential to produce materials and structures with unprecedented mechanical and functional properties.

The cover photo of Compton’s work is related to a review article on different additive manufacturing routes to meso-scale materials included in the issue. A summary of Compton’s work on 3D-printed epoxy composites is included with the article.

MRS Bulletin is one of the most widely recognized and highly respected publications in advanced materials research.