Additive manufacturing of PLA structures using fused deposition modelling: Effect of process parameters on mechanical properties and their optimal selection

FDM process parameters influence over the mechanical properties of polymer specimens: A review

Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, composite 3D printing feedstocks for FFF are investigated, wherein carbon fibres are embedded into a thermoplastic matrix to increase strength and stiffness. First, the key processing parameters for FFF are reviewed, showing how fibres alter the printing dynamics by changing the viscosity and the thermal profile of the printed material. The state-of-the-art in composite 3D printing is presented, showing a distinction between short fibre feedstocks versus continuous fibre feedstocks. An experimental study was performed to benchmark these two methods. It is found that printing of continuous carbon fibres using the MarkOne printer gives significant increases in performance over unreinforced thermoplastics, with mechanical properties in the same order of magnitude of typical unidirectional epoxy matrix composites. The method, however, is limited in design freedom as the brittle continuous carbon fibres cannot be deposited freely through small steering radii and sharp angles. Filaments with embedded short carbon microfibres (∼100 μm) show better print capabilities and are suitable for use with standard printing methods, but only offer a slight increase in mechanical properties over the pure thermoplastic properties. It is hypothesized that increasing the fibre length in short fibre filament is expected to lead to increased mechanical properties, potentially approaching those of continuous fibre composites, whilst keeping the high degree of design freedom of the FFF process.

https://research-information.bris.ac.uk/files/159707908/1_s2.0_S2214860417305687_main.pdf

An investigation into 3D printing of fibre reinforced thermoplastic composites

Three-dimensional (3D) printed scaffold and material selection for bone repair

The objective of this study is to characterize the micromechanical properties of poly-l-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 µm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of the composite was further examined by a representative volume element (RVE) model. The results showed that the interphase layer provided a smooth transition of elastic modulus from steel particles to the polymeric matrix. A 10% volume fraction of steel particles could enhance the elastic modulus of PLLA polymer by 31%. In addition, steel particles took 37% to 59% of the applied load with respect to the particle volume fraction. We found that degradation of the interphase reduced the elastic modulus of the composite by 70% and 7% under tensile and compressive loads, respectively. The shear modulus of the composite with 10% particles decreased by 36%, i.e., lower than pure PLLA, when debonding occurred.

/pdf/mechanical-characterizations-of-3d-printed-plla-steel-dslshaz63i.pdf

Mechanical Characterizations of 3D-printed PLLA/Steel Particle Composites.

Fused deposition modeling (FDM) is a rapidly growing 3D printing technology. However, printing materials are restricted to acrylonitrile butadiene styrene (ABS) or poly (lactic acid) (PLA) in most Fused deposition modeling (FDM) equipment. Here, we report on a new high-performance printing material, polyether-ether-ketone (PEEK), which could surmount these shortcomings. This paper is devoted to studying the influence of layer thickness and raster angle on the mechanical properties of 3D-printed PEEK. Samples with three different layer thicknesses (200, 300 and 400 μm) and raster angles (0°, 30° and 45°) were built using a polyether-ether-ketone (PEEK) 3D printing system and their tensile, compressive and bending strengths were tested. The optimal mechanical properties of polyether-ether-ketone (PEEK) samples were found at a layer thickness of 300 μm and a raster angle of 0°. To evaluate the printing performance of polyether-ether-ketone (PEEK) samples, a comparison was made between the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) and acrylonitrile butadiene styrene (ABS) parts. The results suggest that the average tensile strengths of polyether-ether-ketone (PEEK) parts were 108% higher than those for acrylonitrile butadiene styrene (ABS), and compressive strengths were 114% and bending strengths were 115%. However, the modulus of elasticity for both materials was similar. These results indicate that the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) are superior to 3D-printed ABS.

https://www.mdpi.com/1996-1944/8/9/5271/pdf

Influence of Layer Thickness and Raster Angle on the Mechanical Properties of 3D-Printed PEEK and a Comparative Mechanical Study between PEEK and ABS

Effects of extrusion speed and printing speed on the 3D printing stability of extruded PEEK filament

The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory effect has been little studied. This study used the orthogonal experimental design method to evaluate the influence of the layer thickness H, raster angle θ, deformation temperature Td and recovery temperature Tr on the shape-recovery ratio Rr and maximum shape-recovery rate Vm of 3D-printed polylactic acid (PLA). The order and contribution of every experimental factor on the target index were determined by range analysis and ANOVA, respectively. The experimental results indicated that the recovery temperature exerted the greatest effect with a variance ratio of 416.10, whereas the layer thickness exerted the smallest effect on the shape-recovery ratio with a variance ratio of 4.902. The recovery temperature exerted the most significant effect on the maximum shape-recovery rate with the highest variance ratio of 1049.50, whereas the raster angle exerted the minimum effect with a variance ratio of 27.163. The results showed that the shape-memory effect of 3D-printed PLA parts depended strongly on recovery temperature, and depended more weakly on the deformation temperature and 3D-printing parameters.

Influence of Layer Thickness, Raster Angle, Deformation Temperature and Recovery Temperature on the Shape-Memory Effect of 3D-Printed Polylactic Acid Samples.

Polyphenylene sulfide (PPS) is a high-performance semi-crystalline thermoplastic polymer that is widely used in the automotive, electronics, and aerospace industries, as well as other fields. However, PPS introduces several challenges in fused deposition modeling owing to its inherent properties of crystallization and thermal crosslinking. The present study demonstrates the effects of the thermal processing and heat treatment conditions on the accuracy and mechanical properties of PPS samples three-dimensionally printed through fused deposition modeling. By measuring the degree of crystallinity and thermal crosslinking of three-dimensionally printed PPS samples, we found that the thermal history affects the three-dimensionally printed PPS properties. Results show that the accuracy of three-dimensionally printed PPS samples can be improved by means of air-forced cooling in fused deposition modeling. The balance between mechanical strength and ductility was regulated by altering the heat treatment conditions. This approach is applicable to eliminating the warpage of semi-crystalline polymer in three-dimensional printing (not only for PPS) and provides a method of improving the mechanical properties of three-dimensionally printed PPS samples.

Effect of Thermal Processing and Heat Treatment Condition on 3D Printing PPS Properties.

Manufacturing difficulties, poor strength and foaming result from the high temperature that is used in thermoplastic polyimide (TPI) 3D printing and the high viscosity and water absorption by the TPI. To overcome these difficulties, the water absorption of pure TPI 3D printed filaments and short-fiber TPI composites were analyzed. The relationship between the drying time of pure TPI 3D printed filaments and the tensile strength of 3D printed specimens was studied. The effects of 3D printing speeds, layer thicknesses and filling rates on the tensile strength of the 3D printed parts were studied employed pure TPI, original continuous carbon fiber reinforced TPI (OCC) and separated continuous carbon fiber reinforced TPI (SCC). The mechanical properties of the continuous-carbon-fiber reinforced TPI were tested on TPI 3D printed samples with or without continuous fiber reinforcement. The SCC improved the success rate of the continuous-carbon-fiber reinforced TPI by 3D printing and enhanced the interfacial bonding strength between the continuous carbon fiber and the TPI matrix. The tensile strength of the continuous carbon fiber reinforced TPI was 158% higher than that of the OCC. A strong bonding surface formed between the continuous carbon fiber and the TPI plastic matrix. The tensile and bending strengths of the the SCC samples were 214% and 167% higher than those of pure TPI. SCC 3D printing can enable the printing of complex parts with an excellent interfacial bonding performance, mechanical properties and high temperature resistance, which can be used in the aerospace industry and other fields.

Geng Peng

Papers

Influence of Layer Thickness and Raster Angle on the Mechanical Properties of 3D-Printed PEEK and a Comparative Mechanical Study between PEEK and ABS

Effects of extrusion speed and printing speed on the 3D printing stability of extruded PEEK filament

Influence of Layer Thickness, Raster Angle, Deformation Temperature and Recovery Temperature on the Shape-Memory Effect of 3D-Printed Polylactic Acid Samples.

Effect of Thermal Processing and Heat Treatment Condition on 3D Printing PPS Properties.

Separated 3D printing of continuous carbon fiber reinforced thermoplastic polyimide