Additive Manufactured Parts Produced Using Selective Laser Sintering Technology: Comparison between Porosity of Pure and Blended Polymers.

For different manufacturing processes, porosity occurs in parts made using selective laser sintering (SLS) technology, representing one of the weakest points of materials produced with these processes. Even though there are different studies involving many polymeric materials employed via SLS, and different manuscripts in the literature that discuss the porosity occurrence in pure or blended polymers, to date, no researcher has reported a systematic and exhaustive comparison of the porosity percentage. A direct comparison of the available data may prove pivotal in advancing our understanding within the field of additively manufactured polymers. This work aims to collect and compare the results obtained by researchers who have studied SLS's applicability to different amorphous or semi-crystalline polymers and pure or blended materials. In particular, the porosity values obtained by different researchers are compared, and tables are provided that show, for each material, the process parameters and the measured porosity values.

Effect of Strain Rates and Heat Exposure on Polyamide (PA12) Processed via Selective Laser Sintering.

The use of polymers in the transportation industry represents a great opportunity to meet the growing demand for lightweight structures and to reduce polluting emissions. In this context, additive manufacturing represents a very effective fabrication route for mechanical components with sophisticated geometry that cannot be pursued by conventional methods. However, understanding the mechanical properties of 3D-printed polymers plays a crucial role in the performance and durability of polymer-based products. Polyamide is a commonly used material in 3D printing because of its excellent mechanical properties. However, the layer-by-layer deposition process and ensuing auxiliary steps (e.g., post-processing heating) may affect the microstructure and mechanical properties of 3D-printed nylon with respect to the bulk counterpart. In this work, we explore the effect of displacement rate and heat exposure on the mechanical properties of 3D-printed polyamide (PA12) specimens obtained by selective laser sintering (SLS). Moreover, the thermal characteristics of the powders and sintered material were evaluated using differential scanning calorimetry (DSC). Our results highlight the expected rate dependency of mechanical properties and show that a post-processing heat treatment partly affects mechanical behavior.

A review of patented works on the mechanical characterization of materials at micro- and nano-scale.

In recent years, the development of cost-effective processing techniques, novel design concepts and new materials paved the way to a widespread diffusion of micro- and nano-electro-mechanical systems (NEMS/MEMS). Obviously, the reliability as well as the performance of NEMS/MEMS depend on the corresponding materials properties, which in turn should be determined using ad-hoc small samples fabricated at the relevant size-scale. For this reason, in the last decade research efforts have been devoted to the development of experimental techniques suitable for the mechanical characterization of materials at micro- and nano-scale. There are many contributions stemming from this research area, the purpose of the present work is to give an overview of the most recent patented works. The focus will be directed to selected patents on the mechanical characterization of both micro- and nanosamples, like nanotubes and nanowires. Special emphasis will be given to the methods suited for the determination of elastic properties, fracture resistance and residual stresses of materials.