Printing parameters and mechanical characteristics of thermoplastic polymers for 3D printed hybrid structures
Topic(s) : Special Sessions
Co-authors :
Olga BULDERBERGA (FRANCE), Edmunds ZĪLE , Roberts JOFFE , Jevgenijs SEVCENKO , Andrey ANISKEVICH (LATVIA)Abstract :
Fused filament fabrication (FFF) is a rapidly developing 3D printing technology utilizing a thermoplastic filament that is melted and then extruded through a nozzle. Due to the flexibility of FFF, the printing process can be done using a wide range of different materials, which allows the creation of parts with completely different physical and mechanical properties for various sectors of industry. As a rule, manufacturing companies provide only a limited set of parameters that are insufficient to model the mechanical behavior of FFF structures.
This study aimed to provide a comparative evaluation of the mechanical and physical characteristics of some filament materials used in FFF in terms of testing and printing conditions. For the investigation following samples types were defined: “as-received” filaments, single extruded fibers - fiber obtained with the same nozzle of printer but not stuck to the bed surface, and unidirectional printed specimens. The impact of loading rate, infill density, and printer head nozzle diameter were assessed. The compatibility of different polymer types for hybrid structures was evalu¬ated in the adhesion tests.
Analysis of the porosity of specimens was performed by X-ray microtomography and optical microscopy of a fractured surface, both giving similar results. During printing, a non-equilibrium polymer macromolecular structure was created. The stiffness and strength of the printed specimens were impacted by the stabilization of the macromolecular structure over time. The maximum values were reached for amorphous materials after 24 hours and for semi-crystalline materials after 160 hours. Tensile properties of “as-received” filaments, extruded mono-fibers, and unidirectional printed specimens were compared. In most cases, the elastic modulus of “as-received” filaments were lower than that of the extruded mono-fibers by 12% on average. The effects of layer thickness and nozzle diameter on mechanical properties were investigated. Adhesive properties were studied within a single layer, increasing and decreasing the frequency of laying the material in the sample. The compatibility of different polymer types for hybrid structures was evaluated in the adhesion tests. Tests showed that adhesion at hybrid PLA contact is only slightly affected by the presence of colourant additives in one of the parts. However, approx. 10 times adhesion reduction was observed when one of the parts contained conductive particles.
In this work, a comparative assessment was carried out based on experimental data obtained under the same conditions and using the same methodology. Knowledge of the basic mechanical properties of the original filaments and simple samples is key for further modeling the properties of printed structures and their reliable design.
This study aimed to provide a comparative evaluation of the mechanical and physical characteristics of some filament materials used in FFF in terms of testing and printing conditions. For the investigation following samples types were defined: “as-received” filaments, single extruded fibers - fiber obtained with the same nozzle of printer but not stuck to the bed surface, and unidirectional printed specimens. The impact of loading rate, infill density, and printer head nozzle diameter were assessed. The compatibility of different polymer types for hybrid structures was evalu¬ated in the adhesion tests.
Analysis of the porosity of specimens was performed by X-ray microtomography and optical microscopy of a fractured surface, both giving similar results. During printing, a non-equilibrium polymer macromolecular structure was created. The stiffness and strength of the printed specimens were impacted by the stabilization of the macromolecular structure over time. The maximum values were reached for amorphous materials after 24 hours and for semi-crystalline materials after 160 hours. Tensile properties of “as-received” filaments, extruded mono-fibers, and unidirectional printed specimens were compared. In most cases, the elastic modulus of “as-received” filaments were lower than that of the extruded mono-fibers by 12% on average. The effects of layer thickness and nozzle diameter on mechanical properties were investigated. Adhesive properties were studied within a single layer, increasing and decreasing the frequency of laying the material in the sample. The compatibility of different polymer types for hybrid structures was evaluated in the adhesion tests. Tests showed that adhesion at hybrid PLA contact is only slightly affected by the presence of colourant additives in one of the parts. However, approx. 10 times adhesion reduction was observed when one of the parts contained conductive particles.
In this work, a comparative assessment was carried out based on experimental data obtained under the same conditions and using the same methodology. Knowledge of the basic mechanical properties of the original filaments and simple samples is key for further modeling the properties of printed structures and their reliable design.