Rectilinear Pattern Research Articles

Influence of infill pattern and layer height on surface characteristics and fatigue behavior of FFF‐printed PEEK

AbstractPolyEther Ether Ketone (PEEK) is a leading thermoplastic biomaterial renowned for its exceptional overall properties and suitability for processing via Fused Filament Fabrication (FFF) Additive Manufacturing (AM). Despite its widespread use in industries, its fatigue behavior remains a critically underexplored aspect. This study aims to investigate the fatigue behavior of FFF‐produced PEEK, considering variations in infill pattern (triangular or rectilinear) and layer height (0.15 mm or 0.25 mm). Fatigue tests revealed a significant influence of the infill pattern on fatigue behavior, with the rectilinear pattern outperforming the triangular one. Layer height had a negligible effect when paired with rectilinear infill. Specimens with rectilinear patterns exhibited superior fatigue performance, achieving infinite fatigue life at maximum applied stress around 70% of ultimate tensile stress. Surface roughness assessment and fracture surface analysis at scanning electron microscope enhanced the interpretation of the results. This pioneering study lays the groundwork for future research in design for AM.

The effects of 3D printing designs on PLA polymer flexural and fatigue strength

This study assessed the comprehensive assessment of flexural and fatigue strength of the three-dimensional (3D)-printed polylactic acid (PLA) samples across diverse printing designs and parameters. The experiment framework included a diverse array of printing parameters: layer heights, first layer thicknesses, infill densities, top/bottom infill patterns, extruder temperatures, perimeters, and types of solid layer top and bottom. Our findings suggest that there is an interplay between these parameters and the mechanical properties of PLA specimens. Notably, the fatigue strength of PLA printing specimens is more significantly influenced (0.44%) by an increase in the thickness of the first layer compared to flexural strength (87%). The rate of increase in bending strength is lower in cases of layer height (3.55%) and initial layer height (0.44%) in contrast with other factors. Specimens with an initial layer thickness of 0.4 mm reached the highest number of cycles until failure, recording 21 022 cycles. Furthermore, the study identifies the infill pattern’s impact on strength, highlighting that the line infill pattern type case has the highest bending strength of 75.97 MPa and surpasses the honeycomb pattern in bending strength. Compared to the Honeycomb pattern, the rectilinear design has 2.1% higher bending strength. The number of cycles to failure of the rectilinear pattern is greater than those of the honeycomb pattern. In comparison to other patterns, the Rectilinear Top/Bottom infill pattern has a higher interest rate of 27.5% for bending strength and 200.83% for fatigue strength. Additionally, greater bending and flexural strength are obtained by raising the solid layer top, bottom, and perimeter values, respectively. In comparison to the other temperatures, the bending strength and fatigue strength are highest at 200 °C. Therefore, the first layer height of 0.4 mm, the top/bottom rectilinear infill pattern, the extruder temperature of 200 °C, the perimeter value of 3, the solid layer/top value of 3, and the solid layer/bottom value of 3 are the optimal values for the part subjected to at the same time bending strength combined with fatigue strength. This comprehensive study may provide a broader and deeper understanding of individual and combined effects on an overview of the bending and fatigue strength in connection to printing design and printing parameters, as well as the ideal optimal parameters for 3D printing with the PLA material. Manufacturers and designers can use the recommended parameters to optimize the strength of their printed parts, considering both bending and fatigue performance.

Investigation of 3D printed CF-PETG composites' tensile behaviors: Synergizing simulative and real-world explorations

This paper presents an experimental and numerical analysis of carbon fiber-reinforced thermoplastic polymer (CF-PETG) made using fused filament fabrication (FFF) technology on dumbbell-shaped specimens under static tensile tests for both honeycomb (NIDA) and rectilinear (RECT) fill patterns at different infill densities (20%, 50%, 75%, and 100%). The tensile test is meticulously executed using the state-of-the-art INSTRON 5969 testing apparatus, with a precise displacement speed set at 2 mm per minute, ensuring the utmost accuracy in our measurements. The experimental results show that the mechanical behavior of each specimen is elastoplastic. The honeycomb pattern showed better strength and stiffness when compared to the rectilinear pattern. The Digimat material model allows for the simulation of complex material behavior, including nonlinear and anisotropic behavior, considering microstructure effects. The numerical model developed using Abaqus/Digimat coupling with experimental results shows a good correlation between the obtained results.

Experimental investigation of the effect of infill parameters on dynamic compressive performance of 3D-Printed carbon fiber reinforced polyethylene terephthalate glycol composites

The current investigation evaluates the compressive response of 3D-printed carbon fiber-reinforced PETG thermoplastics to optimize different infill parameters when loaded at high impact pressures (strain rates). The selected parameters for the 3D printing of different samples are the filling pattern (rectilinear and honeycomb) and the filling density (25%, 50%, and 75%). Compression-split Hopkinson pressure bars (SHPBs) combined with a high-speed camera were used to monitor the evolution of the mechanical behavior and damage kinetics of 3D-printed samples in real-time with the variation in strain rate. The results revealed a significant improvement in compressive strength and compressive modulus when the filling density was increased from 20% to 75% for both patterns. However, the combination of a honeycomb pattern with 75% filling presented the best compressive strength, stiffness and damage resistance, irrespective of impact pressure. In particular, the highest compressive strengths, ranging from 35.5 to 56.16 MPa for impact pressures of 1.4 to 2.4 bar, respectively, were obtained with this configuration (75% honeycomb pattern). This represents a substantial difference of 25 to 38% compared with the 75% rectilinear pattern, which showed values below 35 MPa. Another significant result was observed for the compressive modulus, which reached 2787.8 MPa for the honeycomb-filled samples, whereas this value remained below 2000 MPa for the rectilinear pattern.

Effect of Process Parameters on Tensile Strength of Polyethylene Terephthalate Glycol Material Specimens 3D Printed Using Material Extrusion

Material extrusion (ME) or Fused deposition modeling (FDM) is one of the additive manufacturing methods in which the thermoplastic material is heated to the extrusion temperature and then extruded by the nozzle to add layer upon layer to prepare a three-dimensional part. The quality and mechanical properties of the material extruded 3D printed part depends on the selection of process parameter and material used to print any part. So, in the present study, the effect of an individual process parameter such as infill pattern, extrusion temperature and raster angle on the tensile strength of polyethylene terephthalate glycol (PETG) material is observed. It is a thermoplastic material with low cost and higher strength than other polymers. Tensile specimens are 3D printed as per the ASTM standard D638 with different combinations of parameters using the design of experiments and tested using a universal testing machine (UTM). As the outcome of this study, it is observed that the tensile strength increases with an increase in all the selected process parameters. Further, the rectilinear pattern, 240 0C extrusion temperature and 0/+450 raster angle is found to be the optimal set of parameter while the extrusion temperature is obtained as the most influencing parameter using Analysis of Variance (ANOVA). Key Words: analysis of variance, fused deposition modeling, polyethylene terephthalate glycol, process parameters, tensile strength.

An insight into the effect of printing orientation on tensile strength of multi-infill pattern 3D printed specimen: Experimental study

This research aims to investigate printing orientation effect on tensile properties of Multi-Infill Pattern (MIP) specimens fabricated by Fused Deposition Modelling (FDM). The material selected for fabrication of specimen is Poly-lactic Acid (PLA), and the thermal stability of PLA material was examined using Thermal Gravimetric Analysis (TGA). The print orientation selected in this study were flat and on-edge orientation. The up-right orientation was not considered because, in this orientation, the parts are built along the z-axis, which results in minimum strength. The MIP consists of honeycomb, triangular and rectilinear patterns fabricated with 25%, 50%, 75% and 100% infill density. The tensile specimen has been designed as per the ASTM D638 standard. The result represents that the printing orientation has influenced the tensile strength of MIP specimen. Higher tensile strength and tensile strength/mass ratio are observed in the on-edge orientation of MIP specimen. The specimen in on-edge orientation with 100% infill density has resulted in higher tensile strength of 30.91 MPa and tensile strength/mass ratio of 3.87 MPa/g. Based on the literature study, the tensile strength of rectilinear, honeycomb and triangular infill pattern PLA specimen with 80% infill density was 10.48 MPa, 10.72 MPa and 20.39 MPa respectively. Hence it can be concluded that the specimen with a MIP has more tensile strength compared to a single infill pattern specimen. Also, trans-layer failure was observed in MIP specimens printed in both orientations.

Effects of Heat-Treatment on Tensile Behavior and Dimension Stability of 3D Printed Carbon Fiber Reinforced Composites.

This work investigated the effects of heat treatment on the tensile behavior of 3D-printed high modules carbon fiber-reinforced composites. The manufacturing of samples with different material combinations using polylactic acid (PLA) reinforced with 9% carbon fiber (PLACF), acrylonitrile butadiene styrene (ABS) reinforced with 9% carbon fiber (ABSCF) were made. This paper addresses the tensile behavior of different structured arrangements at different% of densities between two kinds of filaments. The comparison of the tensile behavior between heat treated and untreated samples. The results showed that heat treatment improves the tensile properties of samples by enhancing the bonding of filament layers and by reducing the porosity content. At all structure specifications, the rectilinear pattern gives higher strength of up to 33% compared with the Archimedean chords pattern. Moreover, there is a limited improvement in the tensile strength and modulus of elasticity values for the samples treated at low heat-treatment temperature. The suggested methodology to evaluate the tensile behavior of the pairs of materials selected is innovative and could be used to examine sandwich designs as an alternative to producing multi-material components using inexpensive materials.

Effects of infill pattern and density on wear performance of FDM-printed acrylonitrile-butadiene-styrene parts

Abstract Acrylonitrile-butadiene-styrene test specimens were additively manufactured by fused deposition method to investigate the effects of infill pattern and density on wear rate, coefficient of friction, wear mechanisms, and microscopic wear characterization. The surface morphology of specimens was characterized using a scanning electron microscope. Under constant parameters of applied load, sliding speed, and sliding time, wear tests were carried out at room temperature. The study revealed that a grid pattern of high infill density and a honeycomb pattern of low infill density showed the lowest wear rate and lowest coefficient of friction compared to the rectilinear pattern. Infill pattern and density affected the wear rate behavior of specimens directly. Moreover, adhesion between additively manufactured layers along with surface texture affects the wear behavior and wear rate. Increasing infill density allowed poor cooling of previously built layers. Longer process time results in rough surfaces.

“Scene” from inside: The representation of Observer’s space in high-level visual cortex

Human observers are remarkably adept at perceiving and interacting with visual stimuli around them. Compared to visual stimuli like objects or faces, scenes are unique in that they provide enclosures for observers. An observer looks at a scene by being physically inside the scene. The current research explored this unique observer-scene relationship by studying the neural representation of scenes' spatial boundaries. Previous studies hypothesized that scenes' boundaries were processed in sets of high-level visual cortices. Notably, the parahippocampal place area (PPA), exhibited neural sensitivity to scenes that had closed vs. open spatial boundaries (Kravitz et al., 2011; Park et al., 2011). We asked whether this sensitivity reflected the openness of landscape (e.g., forest vs. beach), or the openness of the environment immediately surrounding the observer (i.e., whether a scene was viewed from inside vs. outside a room). Across two human fMRI experiments, we found that the PPA, as well as another well-known navigation-processing area, the occipital place area (OPA), processed scenes' boundaries according to the observer's space rather than the landscape. Moreover, we found that the PPA's activation pattern was susceptible to manipulations involving mid-level perceptual properties of scenes (e.g., rectilinear pattern of window frames), while the OPA's response was not. Our results have important implications for research in visual scene processing and suggest an important role of an observer's location in representing the spatial boundary, beyond the low-level visual input of a landscape.

The effects of infill patterns and infill percentages on energy consumption in fused filament fabrication using CFR-PEEK

PurposeThis study aims to identify the effects of infill patterns and infill percentages on the energy consumption (EC) of fused filament fabrication (FFF). With increasing attention on carbon-fiber-reinforced–poly-ether-ether-ketone (CFR-PEEK) for practical applications in FFF, infill pattern and infill percentage for FFF can be properly controlled to achieve better energy performance of CFR-PEEK outputs. However, the effects of infill parameters on EC for FFF using CFR-PEEK have not been clearly addressed yet.Design/methodology/approachUsing a full factorial experimental design, six types of infill patterns (rectilinear, grid, triangular, wiggle, fast honeycomb and full honeycomb) and four different infill percentages (25%, 50%, 75% and 100%) were considered for a design of experiments with three replicates. Then, analysis of variance, Tukey test and regression analysis were performed to investigate both the effects of infill pattern and infill percentage on energy performance during FFF.FindingsEC is characterized to be high for the wiggle and triangular patterns and low for the rectilinear pattern during both the printing stage and the entire process. The wiggle pattern results in the greatest increase in EC, whereas the rectilinear pattern leads to the least increase in EC. Although EC during the FFF process increases as the infill percentage increases, the average power demand during the printing stage decreases.Originality/valueBoth the main and interaction effects of infill pattern and infill percentage are investigated to estimate EC and power during the different process stages of FFF.

How macroscopic structure of 3D printed protein bars filled with chocolate influences instrumental and sensory texture

The aim of this study was to determine the influence of the macroscopic structure of 3D printed protein bars with chocolate fillings on instrumental texture properties and sensory perception. Protein bars with different printing patterns (layered, rectilinear and concentric) were prepared by extrusion-based 3D printing. We found that protein bars with concentric chocolate infill pattern were significantly harder than bars with a chocolate layer, despite their similar chocolate content. Protein bars with a chocolate layer were significantly more cohesive than bars with a rectilinear pattern. Differences in instrumental texture were explained using spring models. Results of sensory ranking tests (n = 70 participants) were in good agreement with those of instrumental texture analysis. For protein bars with 16 g/100g chocolate content, protein bars with concentric pattern were perceived as the hardest. For protein bars with 25 g/100g chocolate content, protein bars with concentric and rectilinear patterns were both perceived significantly harder than bars with a chocolate layer. No significant differences were found between bars that differed in infill pattern for perceived chewiness and liking. We conclude that by changing the macroscopic structure (printing pattern) of 3D printed protein bars with chocolate fillings, the instrumental and sensory properties can be modified without affecting liking.

Evaluating Stress Relief from Architecture: A Case Study Based on Buildings in Taiwan, China and Japan

The urban landscape can be improved to reduce the stress experienced by citizens. Therefore, stress-relieving buildings constitute a crucial topic and a future trend in architecture and design. In this study, different architectural styles were investigated to explore design methods for and characteristics of stress-relieving building shapes and to identify indicators for measuring participant stress relief while viewing buildings. To understand stress relief from architecture, we performed semi-structured interviews with 60 participants who viewed images of 30 buildings. The semantic differential method with a 7-point image scale was used to rate stress relief from different architectural styles. The study results revealed that the participants perceived curvilinear buildings as interesting but do not relieve stress. The participants identified as feeling high pressure considering rectilinear patterns to relieve more stress. To support this observation, we identified three principles—city image, identity, and spiritual atmosphere—as fundamental loci of designing cities for livability. We illustrate the three principles with several cases that facilitate a detailed understanding of their applicability in biodesign practices.

Assessment of Static Mechanical Properties of Additively Manufactured Polylactic Acid (PLA) on Entry-Level FDM 3D Printer

The paper presents the study on the static mechanical properties of PLA (Polylactic Acid) produced with entry-level additive technologies using three printing directions. During the experimental work were tested a total of 15 �dog bone� ASTM D638-14 standard specimens made from additively manufactured polymer (PLA) through FDM (Fused Deposition Modelling) technique, where the material and rectilinear pattern infill geometry and infill percentage of 100% were constant and the printing orientation was varied. Usually technical data sheets that are delivered by filament materials producers include the most satisfactory data which are valid for only one specific printing direction. The printing direction is deliberately selected, in such way that the best material characteristics are achieved. In addition to this matter, as the additive manufacturing market grew significantly in the past couple of years, the filament production market showed a consequential growth. The aftermath of this expansion had a direct impact towards the quality and costs of the filaments used for 3D printing, in order to satisfy both the low-end and high-end users. Therefore, in this frame, the present research provides entry-level additively manufactured PLA performances showing significant changes depending on the different printing directions and determine the build orientation influence on the mechanical properties, in the aim of providing aid for both mechanical designer and product manufacturer at the stage of the printed product mechanical properties.

Thermotropic liquid crystalline polymer reinforced polypropylene composites enhanced with carbon nanotubes for use in fused filament fabrication

AbstractThe objective of this research was to enhance the mechanical properties of wholly thermoplastic composites (WTCs) used in fused filament fabrication (FFF). Multiscale thermoplastic composites, which were based on the use of polypropylene (PP) reinforced with thermotropic liquid crystalline polymer (TLCP) and carbon nanotubes (CNTs), were prepared by a method combining supercritical carbon dioxide (scCO2)‐aided exfoliation and dual‐extrusion technologies. Significant enhancement of tensile properties was observed by using 1 wt% exfoliated CNTs to reinforce WTCs consisting of PP with and without maleic anhydride‐grafted polypropylene (MAPP, 16 wt%). With 1 wt% CNTs and 16 wt% MAPP dual reinforcement, 20 wt% TLCP reinforced WTCs based on PP exhibited 265%, 274%, and 182% improvement in the tensile modulus of the filaments, laid up specimens in the concentric pattern, and laid up specimens in ±45° rectilinear pattern, respectively. For tensile strength, 1 wt% CNTs reinforcement combined with 16 wt% MAPP improved the 20 wt% TLCP reinforced WTC filaments, laid down parts in the concentric pattern, and ±45° rectilinear patterns by 73%, 53%, and 65%, respectively. The tensile modulus and strength of multiscale WTC based on MAPP/PP specimens laid down with a concentric pattern are higher than those reported for PP/40 wt% short carbon fiber and PP/48.5 wt% short glass fiber laid down specimens. The advanced tensile modulus properties of 1 wt% CNTs reinforced WTCs are competitive with 9 wt% continuous carbon fiber reinforced nylon composite materials in FFF. Scanning electron microscopy analysis showed extremely strong interfacial adhesion between the TLCP fibrils and the matrix in multiscale WTC filaments and laid down parts, compared to the WTCs with no CNTs reinforcement. The advanced interfacial adhesion between TLCP fibrils and matrix resulted in an enhancement in the tensile strength. The exfoliated CNTs were premixed with the matrix, but they were trapped at and aligned with TLCP fibrils, which may be the primary reason for tensile modulus enhancement.

On shear resistance of almond skin reinforced PLA composite matrix-based scaffold using cancellous screw

ABSTRACT The polylactic acid (PLA) matrix is being widely used as a scaffold for biomedical applications. But hitherto little has been reported on the use of 3D printed almond skin (AS) powder-reinforced matrix of PLA as a scaffold for ensuring shear resistance properties at different insertion angle, depth and infill pattern for holding a cancellous screw. This paper reports the shear fracture and morphological features of the 3D printed AS powder-reinforced matrix of PLA, prepared by fused deposition modelling for biomedical scaffolds using a cancellous pedicle screw. The study was performed using the angle of insertion 10°, 20° and 30°, depth of insertion of screw 40%, 70% and 100% in prototype and infill patterns (honeycomb, rectilinear and triangular) of 3D printed functional prototype. The study suggested that the maximum shear strength at peak (23.02 MPa) and maximum shear strength at break (22.90 MPa) were observed for honeycomb printing infill pattern, 100% insertion of screw and at 30° angle of insertion to prototype, whereas maximum modulus of toughness was observed for rectilinear pattern with 100% insertion of screw and 20° angle of insertion. Further morphological study was performed on the fractured surface to support the mechanical results obtained by pull-out test for ensuring shear resistance. Overall the study will be useful for an orthopaedic surgeon for ensuring angle, depth of insertion and infill pattern selection for minimising the shear fracture of the scaffold.

Enhancement of the Compressive Strength of 3D-Printed Polylactic Acid(PLA) by Controlling Internal Pattern

Cost-efficient 3D-printing can create a lot of new opportunities in engineering as it enables rapid prototyping of models and functional parts. In the present study, Polylactic acid (PLA) cubic specimens with different types of infill patterns (IPs), rectilinear, grid and cuboid, were additively manufactured by Fused Filament Fabrication 3D-printing. The PLA cubes are fabricated with one perimeter and different IPs density (10, 20, and 30%). Subsequently, the compressive strengths of the PLA materials were measured in two loading directions, i.e., the layers building direction is parallel (PD) to the loading axis and perpendicular (ND) to the loading direction. An optical microscope was used to examine the deformed IPs in both loading directions. The compressive flow stress curves of the PLA cubes infilled with rectilinear and grid patterns exhibited strong fluctuations with lower compressive strengths in the loading direction along ND. The PLA with 30% grid IP revealed a superior strength of ~12 kN in the loading direction along PD. On the contrary, the same material exhibited a worst compressive strength 3 kN along ND.

Projection-angle-dependent distortion correction in high-speed image-intensifier-based x-ray computed tomography

Geometric distortion is inevitable in facilities using x-ray image intensifiers. When the induced distortion pattern varies over time, each recorded frame should be corrected accordingly, which is the case in conventional C-arm imaging, for example. This demonstrates the need for reliable and easy-to-use, projection-angle-dependent correction methods. In the present work, we demonstrate such a dynamic approach, based on digital image correlation (DIC). We validate the method in a set-up for high-speed x-ray tomography, where the variable distortion is induced by an inhomogeneous distribution of ferromagnetic components in the sample rotation stage. By comparing the ideal positions of metal beads in a rectilinear pattern and their positions in the corrected radiographs of that pattern, we deduced the minimum number of frames required to estimate the varying distortion behavior during a full revolution of the stage. Next, this method was validated in a geometry calibration algorithm for a tomographic set-up, as well as in a tomographic reconstruction. Before the application of any distortion correction, the recorded images suffer from, on average, a mean and maximum distortion of 11.12 pixels (1.56 mm) and 42.79 pixels (6.10 mm), respectively. From our experiments, we conclude that three projections, sampled with a 120° interval, are sufficient to correct any frame recorded under an intermediate angle, with mean and maximum residual errors respectively below 0.48 pixels (0.068 mm) and 1.68 pixels (0.240 mm) while using a 14” image intensifier covering a 292 mm 292 mm field of view. These results imply a decrease of the mean and maximum distortion errors of at least 96%, regardless of the projection angle. Next, the results showed improved accuracy in the system’s geometry calibration, which resulted in a reduced blurring of edges and better contrast, as well as shape preservation in the tomographic reconstruction. This demonstrates that the new method is accurate and reliable and, due to the common availability of DIC software, it is very accessible and easy to use.

Strength and Surface Characteristics of FDM-Based 3D Printed PLA Parts for Multiple Infill Design Patterns

Fused Deposition Modeling (FDM) based 3D printers are gaining popularity as cost-effective printers that are changing the life of millions with their capability to manufacture products in the fields of engineering, medical and education. This paper examines the variation in the compressive strength of FDM processed Polylactic acid (PLA) parts for different infill design patterns. The work is performed on 6 infill designs i.e., Hilbert curve, honeycomb, line, rectilinear, Archimedean curve and octagram spiral and compressive strengths are compared for infill densities varying from 20 till 80% in step of 20. It is observed that the Hilbert curve design exhibits maximum compressive strength of 121.35 MPa which is much higher than other designs rectilinear (78.88 MPa), line (73.84 MPa), honeycomb (62.56 MPa), Archimedean (70.07 MPa), octagram spiral (60.01 MPa). Also, with increase in infill density, compressive strength increases for all the considered infill design patterns. The fabricated parts are also investigated for surface roughness values for best 3 compression strengths with different combinations of infill densities. The surface roughness increases with increase in infill densities for rectilinear and hilbert curve but decreases for line pattern. Rectilinear pattern exhibits lowest roughness value as compared to hilbert curve and line design patterns.

On 3D-printed ZnO-reinforced PLA matrix composite: Tensile, thermal, morphological and shape memory characteristics

The zinc oxide (ZnO)-reinforced polylactic acid (PLA) matrix has established shape memory characteristics. But hitherto little has been reported on two-way programmed 3D-printed ZnO-reinforced PLA functional prototypes (prepared on commercial fused deposition modelling (FDM) set-up). This article reports the effect of 3D printing process parameters on tensile, thermal, morphological and two-way programmed shape memory characteristics of ZnO-reinforced PLA-based functional prototypes. It has been ascertained that the maximum strength at peak (14.32 MPa) and maximum strength at break (12.89 MPa) were observed for sample printed at 80% infill density, four number of perimeters with triangular pattern. Maximum Young’s modulus (233.68 MPa) was observed for samples printed at 80% infill density and three perimeters with honeycomb pattern. Also, the maximum modulus of toughness (0.883 MPa) was observed in case of sample printed at 80% infill density, five perimeters with rectilinear pattern. Further based upon thermal analysis using differential scanning calorimetry, it has been ascertained that there is no significant effect of FDM process parameters on normalized heat capacity of functional prototype. As regards to two-way programmed specimens, it has been observed that the porosity of functional prototypes increase with 30 min immersion in water as stimulus at 70°C and it again decreases (regain) after 30 min exposure at atmospheric temperature. Contrary to this, the samples’ porosity values decrease with 30 min immersion in water at 10°C and regain after 30 min exposure at atmospheric temperature. Further some effect of shape memory has been noticed on functional prototypes volume and weight at two different temperatures.

3D printed porous PEEK created via fused filament fabrication for osteoconductive orthopaedic surfaces

Due to its unique and advantageous material properties, polyetheretherketone (PEEK) is an attractive biomaterial for implantable devices. Though concerns exist regarding PEEK for orthopaedic implants due to its bioinertness, the creation of porous networks has shown promising results for interaction with surrounding tissue. In this study, we created porous PEEK via clinically-available fused filament fabrication (FFF, 3D printing) and assessed the pore structure morphology, mechanical properties, and biologic response. The designs of the porous structures were based on a simple rectilinear pattern as well as triply periodic minimal surfaces (TPMS), specifically gyroid and diamond types. The material characteristics, including porosity, yield strength, and roughness, were evaluated using μCT, static compression testing, and optical profilometry. The porous PEEK, along with 3D printed solid PEEK, was then seeded with MC3T3-E1 preosteoblast cells for evaluation of cell proliferation and alkaline phosphatase (ALP) activity. The samples were then imaged via scanning electron microscopy (SEM) to observe cell morphology. μCT imaging showed the porous networks to be open and interconnected, with porous sizes similar (p > 0.05) to the as-designed size of 600 μm. Average compressive properties ranged from 210 to 268 MPa for elastic modulus and 6.6–17.1 MPa for yield strength, with strength being greatest for TPMS constructs. SEM imaging revealed cells attaching to and bridging micro-topological features of the porous constructs, and cell activity was significantly greater for the porous PEEK compared to solid at multiple time points.