3D printing offers the opportunity to design and make replacement parts to exacting specifications when needed. This is particularly helpful for space applications where stand-alone replacement mechanisms are required. Samples of 3D-printed polylactic acid (PLA) were subjected with up to 200 kGy of gamma radiation from a Cobalt-60 irradiator. The mechanical responses to destructive testing were successfully modeled with a combination of linear and exponential functions and may be understood given the underlying chemical changes due to said radiation exposures. We find that for doses up to 50 kGy, the performance of 3D-printed PLA is largely unaffected, which is beneficial for applications in space and in medicine. At larger doses, it appears that decomposition processes win out over cross-linking, which may aid in the degradation of PLA in waste streams.

Through the past two decades, there has been a continued push for renewable resources and future sustainability of materials and processes. This has prompted more developments of providing environmentally friendly practices and products, both in terms of higher recyclability and greater use of renewable resources. An important area of interest are materials for construction and manufacturing purposes, specifically “green” sustainable reinforcement materials for thermoplastic composite materials. During this time, there has also been an evolution in manufacturing methods. Additive manufacturing (AM) has continued to grow exponentially since its inception for its extensive benefits. This study aims to investigate an additive manufactured composite material that is a greener alternative to other composites that are not reinforced by natural fibers. A bamboo filled polylactic acid (PLA) composite manufactured by fused filament fabrication was evaluated in order to gather mechanical strength characteristics by means of tensile, flexure, compression, impact, and shear tests. In this material, the bamboo reinforcing material and the PLA matrix material can both be sourced from highly renewable resources. In this study, a variety of test samples were manufactured at different manufacturing parameters to be used for mechanical testing. The results were recorded with respect to varying manufacturing parameters (raster angle orientation). It was found that the 0° raster angle orientation performed the best in every category except tensile. Additively manufactured bamboo filled PLA was also seen to have comparable strength to certain traditionally manufactured bamboo fiber reinforced plastics.

A new basalt fiber reinforced acrylonitrile butadiene styrene (ABS) filament has been developed for fused filament fabrication (FFF, 3D printing) to be used in Mars habitat construction. Building habitats on Mars will be expensive, especially if all material must be shipped from earth. However, if some materials can be used from Mars, costs will dramatically decrease. Basalt is easily mined from the surface of Mars. This study details the production process of the material, experimental results from mechanical testing, and preliminary X-ray shielding characteristics. The addition of chopped 3 mm basalt fibers to standard FFF material, ABS, increased strength and stiffness of the composite material. By adding 25% (by weight) basalt fiber to ABS, tensile strength improved nearly 40% by increasing from 36.55 MPa to 50.58 MPa, while Modulus of Elasticity increased about 120% from 2.15 GPa to 4.79 GPa. Flexural strength increased by about 20% from 56.94 MPa to 68.51 MPa, while Flexural Modulus increased by about 70% from 1.81 GPa to 3.05 GPa. While compression results did not see much strength improvements, the addition of fibers also did not decrease compressive strength. This is important when considering that basalt fibers provide radiation shielding and the cost of adding basalt fibers to construction materials on Mars will be negligible compared to the cost of shipping other materials from earth. In preliminary digital radiography testing, it was shown that 77% of X-rays were shielded with 25% basalt fiber added (as compared to neat ABS). In small-scale 3D printing applications, the 25% fiber ratio seems to be the highest ratio that provides reliable FFF printing.

Cellular metamaterials are of interest for many current engineering applications. The incorporation of hierarchy to cellular metamaterials enhances the properties and introduces novel tailorable metamaterials. For many complex cellular metamaterials, the only realistic manufacturing process is additive manufacturing (AM). The use of AM to manufacture large structures may lead to several types of manufacturing defects, such as imperfect cell walls, irregular thickness, flawed joints, partially missing layers, and irregular elastic–plastic behavior due to toolpath. It is important to understand the effect of defects on the overall performance of the structures to determine if the manufacturing defect(s) are significant enough to abort and restart the manufacturing process or whether the material can still be used in its nonperfect state. In this study, the performance of hierarchical honeycomb metamaterials with defects has been investigated through simulations and experiments, and hierarchical honeycombs were shown to demonstrate more sensitivity to missing cell walls than regular honeycombs. On average, the axial elastic modulus decreased by 45% with 5.5% missing cell walls for regular honeycombs, 60% with 4% missing cell walls for first-order hierarchical honeycomb and 95% with 4% missing cell walls for second-order hierarchical honeycomb. The transverse elastic modulus decreased by about 45% with more than 5.5% missing cell walls for regular honeycomb, about 75% with 4% missing cell walls for first-order and more than 95% with 4% missing cell walls for second-order hierarchical honeycomb.