Additive Manufacturing and Injection Moulding of High-Performance IF-WS 2 /PEEK Nanocomposites: A Comparative Study

In this study, PEEK nanocomposites with 0, 0.5, 1, and 2wt% IF-WS2 were manufactured by injection moulding and Fused Deposition Modelling (FDM). To compare the impact of the two processing methods and the incorporated nanoparticles on the morphology, crystallization and final mechanical properties of the nanocomposites, SEM, DSC and tensile testing were performed. In general, a good distribution of nanoparticles was observed in PEEK, although larger agglomerates were visible at 2 wt% IF-WS2. The crystallization degree of PEEK increased with increasing loading of IF-WS2 nanoparticles up to 1wt% and then declined at 2 wt%, due to lower level of particle dispersion in this sample. The 3D printed samples showed slightly higher crystallinity at each IF-WS2 loading in relation to the injection moulded samples and extruded filaments, because of multiple reheating effect from subsequent layer deposition during FDM, causing recrystallization. In general, incorporation of IF-WS2 nanoparticles increased the mechanical properties of pure PEEK in both 3D printed and injection moulded samples. However, this increment was more noticeable in the 3D-printed nanocomposite samples, resulting in smaller gap between the mechanical properties of the 3D-printed samples and the injection moulded counterparts, in respect to pure PEEK, particularly at 1 wt% IF-WS2. This effect is ascribed to the increased inter-layer bonding of PEEK in the presence of IF-WS2 nanoparticles in FDM. In general, the lower mechanical properties of the 3D printed samples compared with the injection moulded ones are ascribed to poor interlayer bonding between the deposited layers and the presence of voids. However, addition of just 1 wt% of IF-WS2 nanoparticles into PEEK increased the tensile strength and Young’s modulus of the FDM PEEK materials to similar levels to those achieved for unfilled injection moulded PEEK. Therefore, incorporation of IF-WS2 nanoparticles into PEEK is a useful strategy to improve the mechanical performance of FDM PEEK

Melt-Blended Multifunctional PEEK/Expanded Graphite Composites

In this work, antistatic, high-performance composites of poly (ether ether ketone) (PEEK) and concentrations of 0.5–7 vol% expanded graphite (EG) were fabricated via twin-screw extrusion and injection moulding at mould temperatures of 200°C. The morphological, electrical, rheological, thermal, mechanical, and wear properties of the composites were investigated. Scanning electron microscope (SEM) images indicate that distribution and dispersion of EG platelets in the PEEK matrix are enhanced at higher EG loadings. The electrical conductivity of the composites with 5 vol% of EG exhibits a sharp rise in the electrical conductivity range of antistatic materials because of the formation of conductive paths. The formation of a three-dimensional EG network led to a rapid increase in the storage modulus of the melt of the 2 vol% of EG-loaded composite at a frequency of 0.1 rad/s and temperature of 370°C. The neat PEEK and composites containing 0.5–5 vol% EG indicated a cold-crystallisation peak in the first heating scan of a non-isothermal differential scan calorimetry (DSC) test and their crystallinity degrees changed slightly. However, after removing their thermal and stress histories, the EG platelets promoted nucleation and increased the PEEK crystallinity remarkably, indicating that annealing of the PEEK composites can improve their mechanical performance. The neat PEEK exhibits the standard tensile and flexural stress-strain behaviour of thermoplastics, and the composites exhibit elastic behaviour initially followed by a weak plastic deformation before fracture. The addition of 5 vol% of EG to PEEK increased the tensile and flexural modulus from 3.84 and 3.55 GPa to 4.15 and 4.40 GPa, decreased the strength from 96.73 and 156.41 MPa to 62 and 118.19 MPa, and the elongation at break from 27.09 and 12.9% to 4 and 4.6%, respectively. The wear resistance of the composite containing 3 vol% EG was enhanced by 37% compared with the neat PEEK

Lap Shear Strength and Fatigue Analysis of Continuous Carbon-Fibre-Reinforced 3D-Printed Thermoplastic Composites by Varying the Load and Fibre Content

This study focuses on evaluating the fatigue life performance of 3D-printed polymer composites produced through the fused deposition modelling (FDM) technique. Fatigue life assessment is essential in designing components for industries like aerospace, medical, and automotive, as it provides an estimate of the component’s safe service life during operation. While there is a lack of detailed research on the fatigue behaviour of 3D-printed polymer composites, this paper aims to fill that gap. Fatigue tests were conducted on the 3D-printed polymer composites under various loading conditions, and static (tensile) tests were performed to determine their ultimate tensile strength. The fatigue testing load ranged from 80% to 98% of the total static load. The results showed that the fatigue life of the pressed samples using a platen press was significantly better than that of the non-pressed samples. Samples subjected to fatigue testing at 80% of the ultimate tensile strength (UTS) did not experience failure even after 1 million cycles, while samples tested at 90% of UTS failed after 50,000 cycles, with the failure being characterized as splitting and clamp area failure. This study also included a lap shear analysis of the 3D-printed samples, comparing those that were bonded using a two-part Araldite glue to those that were fabricated as a single piece using the Markforged Mark Two 3D printer. In summary, this study sheds light on the fatigue life performance of 3D-printed polymer composites fabricated using the FDM technique. The results suggest that the use of post-printing platen press improved the fatigue life of 3D-printed samples, and that single printed samples have better strength of about 265 MPa than adhesively bonded samples in which the strength was 56 MPa

Influence of Ambient Temperature on Part Distortion: A Simulation Study on Amorphous and Semi-Crystalline Polymer

Semi-crystalline polymers develop higher amounts of residual stress and part distortion (warpage) compared to amorphous polymers due to their crystalline nature. Additionally, the FDM processing parameters such as ambient temperature play an important role in the resulting residual stresses and part distortion of the printed part. Hence, in this study, the effect of ambient temperature on the in-built residual stresses and warpage of amorphous acrylonitrile-butadiene-styrene (ABS) and semi-crystalline polypropylene (PP) polymers was investigated. From the results, it was observed that increasing the ambient temperature from 50 °C to 75 °C and further to 120 °C resulted in 0.22-KPa and 0.37-KPa decreases in residual stress of ABS, but no significant change in the amount of warpage. For PP, increasing ambient temperature from 50 °C to 75 °C led to a more considerable decrease in residual stress (0.5 MPa) and about 3% increase in warpage. Further increasing to 120 °C resulted in a noticeable 2 MPa decrease in residual stress and a 3.4% increase in warpage. Reduction in residual stress in both ABS and PP as a result of increasing ambient temperature was due to the reduced thermal gradients. The enhanced warpage in PP with increase in ambient temperature, despite the reduction in residual stress, was ascribed to crystallization and shrinkage