In recent years, the landscape of manufacturing has undergone a paradigm shift with the advent of 3D printing technology. A particularly intriguing development within the realm of 3D printing is the fabrication of continuous fiber reinforced composites.

Unlike traditional composites, where fibers are manually layered, continuous fiber reinforced composites offer seamless integration of fibers into a 3D printed matrix. This results in enhanced strength, stiffness, and overall mechanical performance, rendering these composites ideal candidates for applications where lightweight, robust structures are essential.

In an era of heightened environmental awareness, the sustainability of manufacturing processes has become a critical focal point. This topic delves into the sustainability aspects of 3D printing with continuous fiber reinforced composites. As industries seek eco-friendly solutions, understanding the life cycle analysis of these materials, their recyclability, and their potential to reduce waste becomes imperative.

Additive Manufacturing (AM) brings a lot of opportunities for designers. However, traditional design methodology cannot fully utilize the potential of AM. Topology optimization, part consolidation, lattice structures, and other design tools have been used to innovate the design for AM.

One of my research is to design light-weight structures for aerospace and automobile industries. From topology optimization result, the material can be redistributed in the design domain. The lattice structure can be used as an infill to support the product. It can both increase the robustness of the structure and avoid the need for support structures inside the part.

This design methodology can be used to design most aerospace and automobile parts which require high stiffness-to-weight ratio. Generally, the weight of the part can be reduced while the strength and stiffness of the part still satisfy the functional requirement.

Lattice structure is defined as a structure with intersected struts and nodes in a 3D space. The material distribution of the lattice structure can be controlled by varying the porosity in the space. Therefore, the mechanical performance of lattice structures can be optimized based on the functional requirement.

The stiffness of the lattice structure can be optimized by topology optimization method such as BESO and SIMP. For BESO method, the material is moving from the low stress strut to the high stress strut. It has been used to optimize the wireframe-based lattice structure. SIMP method uses the homogenized property of the unit cell and optimize the relative density of each unit cell. It has been used to optimize the TMPS-based lattice structure.

I have been working on the optimization of lattice structure with Dr. Yunlong Tang and Dr. Dawei Li for many years. We have developed both the simulation model and the optimization algorithm. The in-house code we have can also optimize the solid-lattice hybrid structures, like the control arm shown in the above figure.

Biomedical application often requires customized design, which is not ideal for traditional manufacturing (better for mass production). However, the cost of AM will not increase for customized production. AM has been used to fabricate orthotics, prosthetics, and implants.

AM has been used to fabricate insole or mid-sole as pedorthics. Pedorthics is the management and treatment of conditions of the foot, ankle, and lower extremities requiring fitting, fabricating, and adjusting of pedorthic devices. Pedorthics uses footwear to help ease and treat these foot-related problems.

Lattice structures can be used to design the mid-sole. The softness of the mid-sole can be controlled by the density of the lattice structure. The shape of the mid-sole can be obtained by 3D scanning. A automatic lattice structure generation tool is developed to infill the mid-sole with lattice structures. The density distribution is guided by the simulation result to reduce the stress concentration.

Using additive manufacturing for conformal cooling, not only can the designs be complex and contour along the part surface, but it can also potentially be built quicker than conventional machining. This is even more true for multi-cavity molds utilizing additive manufacturing to build conformal cooling channels. I have worked on the conformal cooling channel design for several case studies.

Conformal cooling can also help to reduce the temperature variance in the injection mold process. By optimizing the space between the cooling channels, the temperature distribution can be maintained in a small range. It can help to reduce the warping effect caused by large temperature difference.

Porous structures can also be used in the conformal fooling channel. The porous structure can serve as a support structure to withstand the load for the injection model. It can also support the cooling channel during the AM fabrication. Meanwhile, the porous structure can also help the heat transferred from the mold to the flow. However, the porous structure will cause the pressure drop in the cooling channel. The optimization of the porous structure in the conformal cooling channel is an interesting topic.

Voxel printing is a promising AM technology that can control the material type voxel by voxel. (Voxel can be considered as a pixel in 3D space.) The voxel size is very small, in a micro-scale. The mechanical property in macro-scale is determined by the material selection in each voxel. Therefore, unlike multi-material printing, voxel printing can enable a smooth transition between materials.

Digitalized materials refer to the material composition can be controlled by digital data. In other words, the material is programmable. Voxel printing can be used to fabricate digitalized materials. By coding the material distribution in each voxel, the overall property of the material can be easily controlled.

The challenge is how to broad the application of voxel printing. The relationship between the material composition and the property needs to be established. Design tools that can fully exploit the potential of voxel printing still needs more development.