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Functionally graded materials (FGMs) gradually change composition throughout their volume, allowing for areas of a part to be optimized for specific performance requirements. While additive manufacturing (AM) process types such as material jetting and directed energy deposition are capable of creating FGMs, design guidelines for varying the material composition in an FGM do not exist. This article presents a novel design solution for FGMs: creating the material gradient by varying the mesostructural size and thickness of bicontinuous, multi-material geometries. By using a bicontinuous structure, such as Schoen's gyroid surface or Schwarz's P and D surfaces, each component material exists as a continuous discrete structure, which allows FGMs to be fabricated by a wider range of AM processes. The gradient is created by varying the volume fraction occupied by the surface structure inside the part volume. This article explores the use of this technique to create FGMs with material extrusion AM. Properties of these bicontinuous structures are experimentally characterized and shown to outperform typical material extrusion FGMs.

The advent of modern digital communication technology has enabled engineers to effectively collaborate regardless of team members’ geographic locations. As such, introducing engineering students to virtual environments and collaborative tools is particularly important to prepare them for careers in increasingly digital environments. This study investigates how integrating online collaboration tools in students’ idea generation activities impacts the i) quantity and ii) variety of ideas generated after a peer-feedback session. Students from five sections of a first-year engineering design course were assigned to either a collocated design team or a non-collocated design team to participate in a collaborative design feedback activity. Students individually generated an idea set using an online brainstorming tool (Stormboard), received peer-feedback via one of two delivery conditions (in-person or virtual through video conferencing), and revised their idea set based on the received feedback. Each final idea set was analyzed and compared to identify any differences in the final idea quantity and variety due to the assigned feedback delivery condition. Results revealed a statistically significant difference, but with minimal realistic impact on the final quantity of ideas (equivalent to a difference of one idea between groups). No statistically significant difference was found in the final variety of ideas generated between collocated and non-collocated design teams after the peerfeedback session. This suggests that feedback provided through digital collaboration tools may be used to support idea generation in non-collocated teams without being detrimental to ideation solutions. The implications of these findings are significant for faculty or students who may be involved in online learning activities centered on engineering design.

Purpose This study aims to investigate the tensile strength and elastic modulus of custom-designed polymer composites developed using voxel-based design. This study also evaluates theoretical models, such as the rule of mixtures, Halpin–Tsai model, Cox–Krenchel model and the Young–Beaumont model and the ability to predict the mechanical properties of particle-reinforced composites based on changes in the design of rigid particles at the microscale within a flexible polymer matrix. Design/methodology/approach This study leverages the PolyJet process for voxel-printing capabilities and a design of experiments approach to define the microstructural design elements (i.e. aspect ratio, orientation, size and volume fraction) used to create custom-designed composites. Findings The comparison between the predictions and experimental results helps identify appropriate methods for determining the mechanical properties of custom-designed composites ensuring informed design decisions for improved mechanical properties. Originality/value This work centers on multimaterial additive manufacturing leveraging design freedom and material complexity to create a wide range of composite materials. This study highlights the importance of identifying the process, structure and property relationships in material design.