Raster Directions Research Articles

Tribology Behavior of In-Situ FDM 3D Printed Glass Fibre-Reinforced Thermoplastic Composites

Fused deposition modeling (FDM) 3D-printed parts are generally weaker compared to injection-moulded parts. Fibre reinforcement is one of the techniques used to enhance the mechanical strength and the tribological behavior of the FDM-printed parts. Recently, a new method for creating FDM 3D-printed composites was developed. Current work focuses on the tribological behavior of the glass fibre-reinforced PLA, manufactured using this new composite manufacturing method. Experiments were conducted to investigate the effect of Glass Fibre (GF) reinforcement on FDM 3D-printed thermoplastic composites, specifically polylactic acid (PLA) under different linear sliding speed and directions. All 3D printed glass fibre-reinforced PLA (PLA-GF) composites exhibited a lower wear rate and a higher friction coefficient compared to 3D printed PLA. Increasing in disc’s linear speed or sliding speed of the pins resulted in a lower coefficient of friction and wear rate. In addition, a perpendicular raster direction towards the disc rotation or pin motion experienced greater friction and greater wear.

Characterization and selection of a skull surrogate for the development of a biofidelic head model

This research paper explores the advancement of physical models simulating the human skull-brain complex, focusing on applications in simulating mild Traumatic Brain Injury (mTBI). Existing models, especially head forms, lack biofidelity in accurately representing the native structures of the skull, limiting the understanding of intracranial injury parameters beyond kinematic head accelerations. This study addresses this gap by investigating the use of additive manufacturing (AM) techniques to develop biofidelic skull surrogates. Materials such as Polylactic Acid (PLA), a bone-simulant PLA variant, and Hydroxyapatite-coated Poly(methyl methacrylate) (PMMA) were used to create models tested for their flexural modulus and strength. The trabecular bone regions were simulated by adjusting infill densities (30%, 50%, 80%) and print raster directions, optimizing manufacturing parameters for biofidelic performance. Among the tested materials, PLA and its bone-simulating variant printed at 80% infill density with a side (tangential) print orientation demonstrated the closest approximation to the mechanical properties of cranial bone, yielding a mean flexural modulus of 1337.2 MPa and a mean ultimate strength of 56.9 MPa. Statistical analyses showed that infill density significantly influenced the moduli and strength of the printed simulants. Digital Image Correlation (DIC) corroborated the comparable performance of the simulants, showing similar strain and displacement behaviors to native skull bone. Notably, the performance of the manufactured cortical and trabecular regions underscored their crucial role in achieving biofidelity, with the trabecular structure providing critical dampening effects when the native bone is loaded. This study establishes PLA, particularly its bone-simulant variant, as an optimal candidate for cranial bone simulants, offering significant potential for developing more accurate biofidelic head models in mTBI research.

What controls layer thickness effects on the mechanical properties of additive manufactured polymers

3D printed artefacts are becoming more common and the effect of printing parameters on their properties is key to their performance in applications. Although parameters like build orientation and raster direction are well-studied the effect of layer thickness (and its introduction of size effects into the properties of the material) is less well-known. This study determines the influence of layer thickness on the mechanical properties of polylactic acid (PLA), acrylonitrile butadiene styrene (ABS) and PETG (polyethlene terephtalate glycol) 3D printed specimens made with fused filament fabrication (FFF). Samples were printed with differing layer thickness and tensile tested according to ASTM D638. The study also found that when increasing the layer thickness the mechanical properties of the specimens for both ABS and PLA decreased. When it came to ultimate tensile strength, the effect of layer thickness on PLA was more significant than on ABS with PETG being in much less significant. The differences were attributed to differences in additive layer adhesion and the effect of the structure and defects introduced by the additive layer process.

Investigation of Raster Pattern Spacing and Direction for Friction Stir Additive Manufacturing of Al-5083

Investigation of Raster Pattern Spacing and Direction for Friction Stir Additive Manufacturing of Al-5083

Investigation of the Tensile Properties in Continuous Glass Fiber–Reinforced Thermoplastic Composite Developed Using Fused Filament Fabrication

Abstract Continuous fiber–reinforced thermoplastic composites are gaining acceptance in the manufacturing sector. However, the production constraints of intricate designs, the difficulty of using unique fiber alignment, and the expensive moldings make their usage inadequate. This investigation attempts to produce composites using continuous glass fiber as filler material and three distinct polymers, acrylonitrile butadiene styrene, polylactic acid, and polyethylene terephthalate glycol, utilizing an indigenously built nozzle attachment with the fused filament fabrication (FFF) process. Furthermore, scanning electron microscopy (SEM) images were used to elucidate the interface performance. The experimental results showed that the tensile strength of glass fiber–reinforced composites was 218 to 241 % greater than that of just thermoplastic specimens when the printing raster direction was 0° and 35 to 45 % lower when the printing raster orientation was 90°. Furthermore, SEM findings revealed that the tensile stress was very low and had bad interface behavior when the printing raster orientation was 90°. FFF has more adaptability for fiber reinforcement because of its meticulous orientation and good dispersal capabilities for the additively manufactured part, which may be directly used as the final product. The fiber content and its interfacing with base material are critical technical specifications for the composites.

An experimental and numerical study of the mechanical response of 3D printed PLA/CB polymers

Fused Filament Fabrication is an Additive Manufacturing method that can produce bespoke components due to the high number of printing parameters available. Each of them plays a significant role in the final mechanical properties of the 3D printed device. This study aimed to uncouple the role of the mesostructure and crystallinity in the final mechanical performance of carbon black/PLA 3D printed samples as a function of the printing parameters. A thermodynamic model was developed to determine the influence of printing parameters, such as nozzle diameter and layer height, in the final crystallinity. Specimens were mechanically tested under uniaxial tensile loads to determine the main deformation and failure mechanisms and results showed that samples were strongly influenced by the printing direction. Furthermore, the nozzle diameter played a significant role in the mesostructure and failure mechanisms, resulting in large differences in ductility for samples printed at raster direction 45°. It was also found that the layer height had a strong influence on the temperature profile and the resulting crystallinity. The importance of crystallinity over porosity to improve the ductility of the material is a substantial contribution to the current state of the art. This work provides the basic fundamentals to manufacturing 3D printed components with tailored mechanical properties for specific loading conditions.

An investigation into the layer thickness effect on the mechanical properties of additively manufactured polymers: PLA and ABS

3D-printed artefacts are becoming more common, and the effect of printing parameters on their properties is key to their performance in applications. Although parameters like build orientation and raster direction are well-studied the effect of layer thickness is less well-known. This study determines the influence of layer thickness on the mechanical properties of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) 3D printed specimens made with fused filament fabrication (FFF). Samples were printed with differing layer thicknesses and tensile tested according to ASTM D638. The study also found that when increasing the layer thickness the mechanical properties of the specimens for both ABS and PLA decreased. When it came to ultimate tensile strength, the effect of layer thickness on PLA was more significant than on ABS. Considering the mechanical properties as well as aspects such as printing time and simplicity of printing, an optimum print setting could be determined. The study found that PLA was more significantly affected by the change in layer thickness compared to ABS.

The effects of processing parameters on mechanical properties of 3D-printed polyhydroxyalkanoates parts

ABSTRACT The crystallisation process of polyhydroxyalkanoates (PHA) polymers plays a key role on final properties of manufactured parts due to most PHA are highly sensitive to physical aging which leads to embrittlement. The secondary crystallisation associated with the aging process can be partially controlled by the cooling process during manufacturing or, even, by heat treatments such as annealing. A critical parameter in additive manufacturing is the difficulty to achieve good adhesion of the material to the printing bed. The bed temperature plays a key role on PHBH crystallisation, which leads to shrinkage having a negative effect on polymer-to-bed adhesion. In this work, a study of the effect of different processing parameters such as the printing temperature, the bed temperature, the cooling conditions, as well as raster direction on the final properties of PHBH 3D-printed parts is carried out.

Tensile failure study of 3D printed PLA using DIC technique and FEM analysis

The paper presents the experimental and numerical study of the failure behaviour of Fused Filament Fabricated (FFF) Polylactic Acid (PLA) samples subjected to tensile load. The examined samples are printed in flat orientation with 0°, 45° and 90° raster angles. During the experiments the deformation of the specimens is continuously scanned with the 3D Aramis measuring system utilizing the digital imaging correlation technique, enabling the determination of strain and stress distribution. In the modelling, it is assumed that each printed layer is a homogeneous transversely isotropic medium with the raster direction treated as the favoured one. The finite element models are developed in the Abaqus-Standard package. A two-dimensional equivalent single-layer approach is utilized to describe the deformation and stress state of the samples. The failure progress of the material is simulated by making use of the Hashin damage algorithm with energy-based softening, whereas the non-linear in-plane shear behaviour is included.

Descriptive and inferential study of hardness, fatigue life, and crack propagation on PLA 3D-printed parts

This research work deals with the development of a methodology for the preliminary assessment of hardness, fatigue, and crack propagation performance of plastic parts manufactured employing polylactic acid (PLA), deposited layer by layer using Fused Filament Fabrication (FFF) technology. A commercial polylactic acid filament was used to print different sample geometries to assess shore D hardness and its correlation with raster direction angles of 0°, 0°/90°, and 0°/45°/− 45°, relative to a reference point, and with three different heat treatment temperatures namely 60 °C, 100 °C, and 140 °C. Additionally, fatigue life and crack propagation were assessed as a function of raster direction angle. Finally, a statistical modeling methodology was employed to obtain both linear equations and response surface plots to correlate performance with layer orientation and heat treatments. The results showed that samples produced at 0°/90° and 0°/45°/− 45° raster direction angles and heat-treated at 100 °C showed the highest hardness performance. Also, the samples produced at 0°/45°/− 45° raster direction angle showed the lowest crack propagation rate until a 200 µm length was achieved, after that the crack rate increased abruptly, reaching 1500 µm at around 4500 fatigue cycles; the 0°/90° raster direction angle reached a crack length of approximately 800 µm at the same number of cycles. The fatigue results showed that samples printed at 0°/45°/− 45° raster direction angles showed a fatigue life of 18,505 cycles, which is above the fatigue life found in samples produced employing the 0° and 0°/90° raster direction angles. The statistical analysis derived from the obtained results shows that the raster direction angle is key to defining the bulk properties of the 3D-printed PLA parts. It was also demonstrated that the use of statistical modeling is a design alternative in contrast to the theory of laminates for composites, which is worth studying and developing for the manufacturing of mechanical parts by 3D printing.

Fracture behavior of anisotropic 3D-printed parts: experiments and numerical simulations

The extrusion-based additive manufacturing (AM) is currently the most common there-dimensional (3D) printing for the fabrication of polymer components. In this study, the fracture behavior of 3D-printed polymer parts is investigated. To this aim, polylactic acid material (PLA) was used to print intact and defected specimens based on the fused deposition modeling (FDM) process. The specimens were printed with three different raster directions to determine their effect on the fracture behavior of the parts. Moreover, wood-reinforced PLA material was used to print another group of test coupons. All specimens were subjected to a series of tensile tests and their fracture behaviors are investigated. Based on the comparison of the results, the influence of reinforcement is determined. In addition, parallel to the experiments, a series of finite element analyses were conducted utilizing the anisotropic phase-field fracture model. For an efficient calculation, we treated the whole specimen as a homogenized solid where the anisotropic property of the layered material is considered in the formulation. By calibrating the model based on the experimental measurement, one can predict the anisotropic fracture behavior of the 3D-printed part with high precision. Since applications of 3D-printed composites have been significantly increased, the results of this study can be used for optimization, further numerical analysis, and next development.

Topology optimization of the vibrating structure for fused deposition modelling of parts considering a hybrid deposition path pattern

ABSTRACT Frequency optimization plays a vital role in designing machines and structures to avoid destructive responses caused by external excitation. In the current study, most frequency optimization research focuses on algorithm innovation to pursue better numerical results. However, with the development of additive manufacturing, increasingly more organic structures produced by topology optimization can be physically fabricated. Therefore, the combination of topology optimization and additive manufacturing is promising and widely investigated. This paper proposes a concurrent topology optimization method for maximizing the natural frequency of Fused Deposition Modelling (FDM) parts printed by a Hybrid Deposition Path (HDP) pattern. The proposed algorithm concurrently optimizes the shape of the structure and the raster directions of the substrate domain, wherein the method of solid orthotropic materials with penalization (SOMP) with double layers of smoothing and projection (DSP) is adopted. A dedicated sensitivity analysis is performed on both the topology and direction variables. Several numerical results are studied to show the effectiveness of the proposed method is efficient and to disclose the influence of raster direction on the vibration model. This work would be instructive to design for FDM printing.

Fracture studies of 3D-printed PLA-wood composite

Additive manufacturing (AM) has shown extraordinary growth over the past few years. In this three-dimensional (3D) printing, the final products are made by adding material layer-upon-layer. Although mechanical behavior of 3D-printed Polylactic Acid (PLA) parts have been investigated in several research works, there are a few studies on the mechanical characterization of 3D-printed PLA-wood composites. In the present study, fracture behavior of intact and defected PLA-wood composite specimens were investigated. To this aim, wood-reinforced PLA material was used to print test coupons. It should be pointed out that the missing extrudates were considered as an intentional defect in the defected specimens. In this study, both groups of intact and defected composite specimens were printed with different raster directions. Based on a series of tensile tests, fracture load and stiffness of the examined parts were determined. Moreover, effects of raster orientations on the fracture behavior of the intact and defected parts were investigated. In this study, the obtained results of tests on intact and defected specimens were compared. This comparison indicated impacts of the defects on the fracture behavior of additively manufactured composite.

Effect of a Powder Mould in the Post-Process Thermal Treatment of ABS Parts Manufactured with FDM Technology.

The post-process thermal treatment of thermoplastics improves their mechanical properties, but causes deformations in parts, making them unusable. This work proposes a powder mould to prevent dimensional part deformation and studies the influence of line building direction in part deformations in a post-process thermal treatment of 3D printed polymers. Two sets of ABS (acrylonitrile butadiene styrene) test samples manufactured by fused deposition modelling (FDM) in six different raster directions have been treated and evaluated. One set has been packed with a ceramic powder mould during thermal treatment to evaluate deformations and mould effectiveness. Thermogravimetric tests have been carried out on ABS samples, concluding that the thermal treatment of the samples does not cause degradations in the polymeric material. An analysis of variance (ANOVA) was performed to study internal building geometry and mould influence on part deformation after the thermal treatment. It can be concluded that powder mould considerably reduces dimensional deformations during the thermal treatment process, with length being the most affected dimension for deformation. Attending to the length, mould effectiveness is greater than 80% in comparison to non-usage of moulding, reaching 90% when the building lines are in the same direction as the main part.

Fracture behavior of intact and defected 3D-printed parts

Additive manufacturing (AM) is a highly innovative technology with advantages over conventional manufacturing processes. AM also known as three-dimensional (3D) printing is a set of manufacturing methods which can be used to produce functional end-use products from 3D solid models. Since 3D-printed components have been used as spare parts and final products, their structural performance become an important issue. The present work aims to determine influence of fabrication defect on structural performance and fracture behavior of 3D-printed parts. To this aim, polylactic acid material was used to print specimens based on fused deposition modeling process. These polymeric specimens were printed with two different raster directions. Moreover, the 3D-printed specimens were subjected to accelerated thermal ageing tests. In this study, a series of tensile tests was conducted on unaged and aged test coupons to determine influence of this thermal ageing on the mechanical behavior of the examined parts. This study sheds light on durability of additively manufactured parts.

An investigation on viscoelastic characteristics of 3D-printed FDM components using RVE numerical analysis

Fused deposition modelling (FDM) has emerged as an economical additive manufacturing method having the potential to fabricate functional components. Dynamic behaviour of FDM components is of great interest while designing and printing them for functional applications. This paper presents a methodology to describe the dynamic characteristics of FDM, combining the features of thermoplastic material and build parameters adopted in fabrication. The viscoelastic characteristics of thermoplastic filament induce time–temperature dependence in FDM components. The viscoelastic characteristic of the polymer is determined by dynamical mechanical analysis. Layer height is a significant build parameter that determines void geometry even in 100% infill printing, that influences mechanical properties of these additive manufactured components. Dynamic response of FDM 3D-printed parts is highly dependent on viscoelastic characteristics of polymer filaments and build parameters associated with printing. In the study, micro-scale models representing the features of actual cross section morphology with different layer heights are identified as representative volume element (RVE) models. Harmonic analysis is conducted on the RVE models using polymer material data approximated with generalized Maxwell model to determine the dynamic characteristics of the FDM print. The numerical analysis reveals orthotropic viscoelastic nature with maximum stiffness along the direction of filament deposition (raster) direction followed by transverse and vertical directions. A drastic reduction in the FDM component stiffness was observed at lower straining rates. The characteristics determined on RVE can be homogenized to the entire structure based on its print conditions and can be used for designing functional components.

The influence of 3D printing process parameters on the mechanical performance of PLA polymer and its correlation with hardness

The present research aims to investigate the impact of various 3D printing process settings on the tensile strength and hardness properties of PLA polymer. Fused deposition modeling (FDM) technique was employed to fabricate the testing specimens with different build orientation, raster direction angle, and layer height. The experiments were also aided with optical microscopic images to identify the 3D print surface structure and quality. The fracture patterns were also specified. To bridge the knowledge gap surrounding 3D-printed material behavior, a correlation between the hardness and tensile strength was assessed based on the performance attained from the examined print parameters. Limited attention was given to this relationship in literature. This indicates the need for evaluating this correlation to understand the 3D fabricated material behavior entirely. The obtained results show that the highest Young’s modulus and ultimate tensile strength values were observed in the On-edge orientation samples (1.896 ± 0.044 GPa and 49.12 ± 0.78 MPa, respectively). Meanwhile, the best elongation at break was found in the 0.1 mm layer thickness specimen (3.13%). Further, it was noticed that the hardness and tensile strength are in a proportional relation when the print orientation parameter is the variable.

Accuracy investigation of 3D printed PLA with various process parameters and different colors

The accuracy of three-dimensional (3D) printing is how the dimensions of a measured product are close to its original model's nominal values. Thus, dimensional accuracy is essential for determining the machine's reliability to produce each object according to the expected results. In this study, the influence of 3D printing process parameters on the dimensional accuracy of specimens manufactured using Polylactic acid (PLA) material is investigated. Based on fused deposition modeling (FDM) technology, cylindrical and dog-bone tensile test samples are fabricated at various process parameters, including build orientation, raster direction angle, and layer thickness. PLA filaments with three different colors (white, grey, and black) are utilized to produce the required test pieces. The dimensional accuracy for cylindrical (diameter and length) and dog-bone (width and thickness) samples have been evaluated. The nominal values are considered the reference to determine the accuracy percentage for each specimen. The weight of all test pieces is also examined, and its precision is assessed. The optimum process parameter settings have been defined to minimize the error percentage in the dimensions of the printed parts. According to the results, a high overall dimensional accuracy of 98.81% was achieved, which indicates the ability of commercial FDM 3D printers as an inexpensive and decent quality alternative for producing utilitarian parts. The filament's color displayed a notable impact on the test pieces' weight, where the difference between the heaviest (white) and lightest (black) specimens is almost a percentage of 7.24%. A remarkable influence was noticed for the layer thickness parameter on the accuracy, meanwhile the raster direction angle parameter appeared no effect when the number of layers and the contour size are the same. The data obtained from this study might help identify the optimum configurations that guide the production of components using thermoplastic filaments through FDM 3D printing.

Influence of the 3D Printing Process Settings on Tensile Strength of PLA and HT-PLA

Fused Deposition Modelling (FDM) is presently the most common utilized 3D printing technology. Since this printing technology makes the bodies anisotropic, therefore, investigate the process with different settings is worthwhile. Tensile test specimens of two plastics have been carried out to examine the mechanical properties. Polylactic acid (PLA) and High Temperature PLA (HT-PLA) are the used materials for this purpose. A total of seventy-two test pieces of the two used polymers were printed and evaluated. Three parameters were examined in twelve different settings when printing the tensile test specimens. The considered settings are; six raster directions, three build orientations and two filling factors. The differences in stress-strain curves, tensile strength values and elongation at break were compared among the tested samples. The broken specimens after the tensile test are illustrated, which gave insight into how the test pieces printed with different parameters were fractured. The optimum printing setting is represented at crossed 45/−45° raster direction, X orientation and 100 % fill factor, where the highest tensile strength of 59.7 MPa at HT-PLA and the largest elongation of about 3.5 % at PLA were measured.

Anisotropy Evaluation of Different Raster Directions, Spatial Orientations, and Fill Percentage of 3D Printed PETG Tensile Test Specimens

In this paper, the mechanical properties of Polyethylene terephthalate-glycol (PETG) tensile test specimens have been investigated. The test pieces were prepared using fused deposition modelling (FDM) 3D printing technology. Three print settings were examined which are: raster direction angles, print orientations, and infill percentage and patterns in order to evaluate the anisotropy of objects when employing FDM print method. The variations in stress-strain curves, tensile strength values and elongation at break among the tested samples were studied and compared. Illustration for the broken specimens after the tensile test was accomplished to know how the test pieces printed with various parameters were fractured. A comparison with some previous results regarding the elongation at break has been carried out.