Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

TL;DR

This paper demonstrates the fabrication of a porous composite with negative thermal expansion using multi-material photopolymer additive manufacturing, employing topology optimization to design internal geometries that achieve the desired thermal properties.

Contribution

It introduces a novel method of creating negative thermal expansion composites via multi-material AM with topology-optimized internal structures.

Findings

Specimens exhibited negative thermal expansion near room temperature.

Topology optimization effectively minimized thermal stress and maximized stiffness.

The method enables rapid fabrication of functional composite materials.

Abstract

Additive manufacturing (AM) could be a novel method of fabricating composite and porous materials having various effective performances based on mechanisms of their internal geometries. Materials fabricated by AM could rapidly be used in industrial application since they could easily be embedded in the target part employing the same AM process used for the bulk material. Furthermore, multi-material AM has greater potential than usual single-material AM in producing materials with effective properties. Negative thermal expansion is a representative effective material property realized by designing a composite made of two materials with different coefficients of thermal expansion. In this study, we developed a porous composite having planar negative thermal expansion by employing multi-material photopolymer AM. After measurement of the physical properties of bulk photopolymers, the internal geometry was designed by topology optimization, which is the most effective structural optimization in terms of both minimizing thermal stress and maximizing stiffness. The designed structure was converted to a three-dimensional STL model, which is a native digital format of AM, and assembled as a test piece. The thermal expansions of the specimens were measured using a laser scanning dilatometer. The test pieces clearly showed negative thermal expansion around room temperature.