A novel practical method for the production of Functionally Graded Materials by varying exposure time via photo-curing 3D printing

Abstract

Functionally Graded Materials (FGMs) are one category of composites suitable for situations requiring conflicting properties in one component. Due to the limitations of conventional manufacturing techniques for FGMs, Additive Manufacturing (AM) as a promising candidate has been widely utilized in recent years. Among AM methods, photo-curing 3D printing is a high-precision method that can produce FGMs. In this article, for the first time, a novel practical technique for printing FGMs is introduced based on changing exposure time without additional cost and equipment. For evaluation, a sample whose layers were printed with different exposure times from 4 s to 46 s with 6 s intervals and a nanoindentation test was conducted to measure Young's modulus in selected layers. The tensile test results illustrated that the average values of Young's modulus and ultimate tensile strength of specimens cured for 46 s were 4.76 and 2.17 times as large as those of cured for 4 s, respectively. Also, the maximum amounts of toughness and elongation belonged to the samples printed with 16 s exposure time. In the final parts, three types of cellular solids were fabricated to show the feasibility of the novel method for building complex components. In addition, compression tests were conducted to reveal the behaviours of samples.