Design and Modification of a Material Extrusion 3D Printer to Manufacture Functional Gradient PEEK Components

Mechanical Behavior of 3D-Printed Thickness Gradient Honeycomb Structures

In order to obtain a lightweight, high-strength, and customizable cellular structure to meet the needs of modern production and life, the mechanical properties of four thickness gradient honeycomb structures were studied. In this paper, four types of honeycomb structure specimens with the same porosity and different Poisson's ratios were designed and manufactured by using SLA 3D-printing technology, including the honeycomb, square honeycomb, quasi-square honeycomb, and re-entrant honeycomb structures. Based on the plane compression mechanical properties and failure mode analysis of these specimens, the thickness gradient is applied to the honeycomb structure, and four structural forms of the thickness gradient honeycomb structure are formed. The experimental results show that the thickness gradient honeycomb structure exhibits better mechanical properties than the honeycomb structure with a uniform cellular wall thickness. In the studied thickness gradient honeycomb structure, the mechanical properties of the whole structure can be significantly improved by increasing the thickness of cell walls at the upper and lower ends of the structure. The wall thickness, arrangement order, shape, and Poisson's ratio of the cell all have a significant impact on the mechanical properties of the specimens. These results provide an effective basis for the design and application of cellular structures in the future.

Experimental Study of the Tensile Behavior of Structures Obtained by FDM 3D Printing Process

Fused Deposition Modelling (FDM) is one of the layer-based technologies that fall under the umbrella term "Additive Manufacturing", where the desired part is created through the successive layer-by-layer addition process with high accuracy using computer-aided design data. Additive manufacturing technology, or as it is commonly known, 3D (three-dimensional) printing, is a rapidly growing sector of manufacturing that is incorporated in automotive, aerospace, biomedical, and many other fields. This work explores the impact of the Additive Manufacturing process on the mechanical proprieties of the fabricated part. To conduct this study, the 3D printed tensile specimens are designed according to the ASTM D638 standards and printed from a digital template file using the FDM 3D printer Raise3D N2. The material chosen for this 3D printing parameter optimization is Polylactic acid (PLA). The FDM process parameters that were studied in this work are the infill pattern, the infill density, and the infill cell orientation. These factors' effects on the tensile behavior of printed parts were analyzed by the design of experiments method, using the statistical software MINITAB2020.

Microstructural and Hydrophilic Properties of Polylactide Polymer Samples with Various 3D Printing Patterns

The aim of the work is to study the effect of the 3D printing process on the microstructural and hydrophilic properties of polylactic acid (PLA) samples with various model printing patterns obtained from the black filament PLA by sequentially applying polymer layers using the FDM (fused deposition modeling) method. X-ray phase analysis revealed the partial crystallization of PLA polymer chains in the printed samples, which occurs under thermal and mechanical action on the original amorphous PLA filament during 3D printing to varying degrees, depending on the geometry of the pattern and the morphology of its surface. At the same time, IR spectroscopy data indicate the preservation of all intrastructural chemical bonds of polylactide. Measured at the original installation, the values of the wetting edge angles on the surface of the printed samples are in the range φ = 50-60°, which is significantly less than the right angle. This indicates the hydrophilic properties of the whole sample's surface. At the same time, the influence of different geometries of model drawings in printed samples was found not only on the morphology of the sample's surface according to SEM data but also on its wettability.

A Review of Print Heads for Fused Filament Fabrication of Continuous Carbon Fiber-Reinforced Composites

The print head is one of the most critical components in an additive manufacturing (AM) system. It can significantly affect the quality of printed parts. Recently, because continuous carbon fiber-reinforced composites can have excellent mechanical properties, a relevant AM technique, fused filament fabrication (FFF), has been attracting increasing attention. This has extended the requirements demanded of print heads. To this end, different FFF extrusion methods have been rapidly developed based on various methods of impregnating fibers into the matrix for the corresponding print heads. Generally, these extrusion methods are of three types: single extrusion, in situ extrusion, and dual extrusion. All these methods face substantial challenges, such as the nozzle clogging and damage to the continuous carbon fibers during extrusion. These common issues still need to be fully addressed. This study's aim is to summarize and discuss the different extrusion methods and their FFF specific components in terms of their advantages and disadvantages for continuous carbon fiber-reinforced composites.

Adaptable polyaryletherketones (PAEKs) with competing crosslinking and crystallisation mechanisms

Driven by the need to make high temperature thermoplastic polymers more processable and expand the range of applications, this study reports on the properties of a novel PAEK material developed by Victrex (Thornton Cleveleys, UK) which is capable of undergoing crosslinking or crystallisation, two competing processes that can be adapted via specific processing temperature and time conditions. The uniqueness of this PAEK material resides in its manufacturing approach, where the crosslinkers are incorporated during the polymerisation process, and its distinct properties, including a controllable viscosity that can be tuned from low to high to allow its application in complex manufacturing processes, such as thermoplastic carbon fibre manufacturing.

Advanced FFF of PEEK: Infill Strategies and Material Characteristics for Rapid Tooling

Traditional vulcanization mold manufacturing is complex, costly, and under pressure due to shorter product lifecycles and diverse variations. Additive manufacturing using Fused Filament Fabrication and high-performance polymers like PEEK offer a promising future in this industry. This study assesses the compressive strength of various infill structures (honeycomb, grid, triangle, cubic, and gyroid) when considering two distinct build directions (Z, XY) to enhance PEEK's economic and resource efficiency in rapid tooling. A comparison with PETG samples shows the behavior of the infill strategies. Additionally, a proof of concept illustrates the application of a PEEK mold in vulcanization. A peak compressive strength of 135.6 MPa was attained in specimens that were 100% solid and subjected to thermal post-treatment. This corresponds to a 20% strength improvement in the Z direction. In terms of time and mechanical properties, the anisotropic grid and isotropic cubic infill have emerged for use in rapid tooling. Furthermore, the study highlights that reducing the layer thickness from 0.15 mm to 0.1 mm can result in a 15% strength increase. The study unveils the successful utilization of a room-temperature FFF-printed PEEK mold in vulcanization injection molding. The parameters and infill strategies identified in this research enable the resource-efficient FFF printing of PEEK without compromising its strength properties. Using PEEK in rapid tooling allows a cost reduction of up to 70% in tool production.