Mechanical compression behavior of reinforced and unreinforced thermoplastic film materials as high-performance core layer for semi-finished sandwich products

Over the last years, the use of high performance thermoplastic materials increased significantly especially in aviation applications. Thus, the processing of these high temperature polymers became more and more interesting. Especially, the groups of polymers like polyphenylene sulfide (PPS), polyether ether ketone (PEEK) or polyetherimide (PEI) are in the focus of recent developments and investigations. These materials show excellent thermal, mechanical and chemical properties while processing remains still challenging. Especially the influence of processing temperatures, temperature depending viscosities, the specific heat capacities and the thermal expansion show a high impact to the quality of the produced parts, e.g. degradation and dimensionally stability. Thus, this paper shows experimental characterizations in regard to the processing of PEI by pipe extrusion processes. In this context, a suitable methodology for the determination of appropriate process parameters is shown, which includes the comprehensive determination of temperature dependent thermal, thermomechanical and degradation properties of specific PEI extrusion materials.

Fused Filament Fabrication (FFF) is an addictive manufacturing process based on the extrusion of a continuous filament of thermoplastic material. There are several materials that are suitable for this production process, including high-performance plastics such as Polyether Ether Ketone (PEEK) or Polyetherimide (PEI). These high-performance thermoplastics produce components with higher strength and toughness than the standard printing plastics, as well as optimized thermal properties.A machine was designed and developed to produce specimens in these high-performance thermoplastics for further study of their physical and mechanical performance. This machine was designed using the CubeX 3D printer produced by 3D Systems as a base, retaining the main essential structure and kinematics to which several modifications were made so that it can work under the extreme operating conditions required for printing these materials. The main changes made to the original machine were the control board, that was replaced by the Duet 2 Wi-Fi Board, the extruder, changed to the E3D Titan Aqua and the build plate which was replaced by with the E3D High Temperature Heated Bed. In addition, a custom glycol-based cooling setup was implemented to cool both the extruder and the machine’s stepper motors, along with the development of a custom heating system for the printing environment.The proposed system has been successfully constructed, being able to produce functional parts in both PEEK and PEI plastics. Further research on the mechanical properties of the specimens produced is in progress.

The present work is concerned with adhesive bonding of thermoplastic composites used in general aerospace applications, including polyphenylene sulfide (PPS), polyetherimide (PEI) and polyetheretherketone (PEEK) carbon fibre composites. Three different surface treatments have been applied to the PEEK, PPS and PEI-based composites in order to enhance the adhesion: atmospheric plasma, ultraviolet radiation (UV) and isopropanol wiping as a control. Water contact angles and free surface energies were measured following the standard experimental procedure based on the employment of three different liquid droplets. Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) were subsequently performed to characterize the surface chemistry of the samples after treatment. The single lap joints were manufactured and bonded by an Aerospace grade epoxy-based film adhesive originally developed for use on metals but with the ability to bond treated thermoplastics to good strength (supplied by Henkel Ireland). Quasi-static (QS) tests were conducted. The lap shear strength was evaluated, and the failure mechanisms of the different joints were examined for the range of surface treatments considered. It was found that the performances of the PEEK and PPS joints were considerably improved by the plasma and UV treatments resulting in cohesive and delamination failures, while PEI was unaffected by the plasma and UV treatments and performed very well throughout.

Real-time structural health monitoring of carbon fiber-reinforced plastic sandwich structures with carbon nanotube-dispersed core using electromechanical behavior data

Crushing behaviour of corrugated tilted honeycomb core inspired by plant stem

ABSTRACTUltra‐high performance thermoplastic polymers (UHTP) are a category of materials with high thermal stability, mechanical strength, and resistance to corrosion and wear. The composites made from such polymers reflect their retention of high‐performance characteristics under extreme conditions, thus rendering their suitability for structural, aerospace, and nuclear applications. Unlike thermosetting polymer‐based composites, thermoplastic polymer‐based composites are recyclable, thus reducing the generation of waste. This paper reviews the recent developments, challenges, and future trends in the application of ultra‐high performance thermoplastic composites such as PEEK (Poly Ether Ether Ketone), PAEK (Poly Aryl Ether Ketone), PEI (Poly Ether Imide) and PEKK (Poly Ether Ketone Ketone) based composites that were fabricated by various processing techniques. There is an elucidation of the structure–property relationship of each of these composite materials, as well as their mechanical properties and the various processing techniques adopted in recent works involving these high‐performance thermoplastics. The challenges in fabrication, processing, and treatment procedures have also been highlighted. High performance thermoplastics are the future super materials that can go a long way toward revolutionizing material technology. Thus, an effort is made here to pave the way for future research and development in the field of lightweight high strength composites as a futuristic trend with the dissemination of data obtained from a review of the latest research work in the field of ultra‐high performance composites.

Recently, high-performance polymers (HPP) have been exploited in the world of additive manufacturing (AM) as a result of improved techniques and the ability to process these materials which require higher processing temperatures. These materials present enhanced mechanical properties, chemical resistance, and thermal stability, increasing AM potentials beyond prototyping applications. Polyether ether ketone (PEEK) has been recognised for its mechanical properties due to its semi crystalline nature and established itself as a biomaterial, possessing biocompatibility and chemical resistance. Polyetherimide (PEI) is renowned for its thermal stability and has been utilised in high temperature-dependent applications. PEEK and PEI are one of the few miscible blends of HPPs, characterized through the presence of a single glass transition temperature. Both materials individually present properties which make them ideal for biomedical applications and through the blending of these materials the biomedical industry could benefit from the synergistic outcome. This review paper will look at PEEK, PEI, and their blends, focusing on the printing parameters, crystallinity and reinforcements. It will also take a look at some of the areas which PEEK and PEI are currently being used, including, implants, prosthetics, and Tissue Engineering.

Behaviour of sandwich structures with cork compound cores subjected to blast waves

10 - The fatigue behavior of composite materials for high-temperature applications

Time‐dependent variable stresses that occur in composites subjected to mechanical and dynamic loads have devastating impacts on the material properties. Since these stresses reduce the service life, it is critical to detect and enhance structural responses before and after dynamic loadings. Therefore, the present study aimed to increase the toughness and delamination resistance of the conventional fiber‐reinforced composites by means of thermoplastic veil interleaves, thereby improving the vibration responses both before and after low‐velocity impact (LVI). In this context, carbon fiber (CF) and glass fiber (GF) reinforced epoxy composites interleaved with five different thermoplastic veils as Polyamide (PA), Polyetheretherketone (PEEK), Polyetherimide (PEI), Polyimide (PI) and Poly‐Phenylene Sulphide (PPS) were manufactured, and machined in accordance with the LVI standard. Composite specimens were subjected to the LVI tests, and then vibration tests were carried out for the non‐impacted and impacted specimens to determine dynamic properties. As a result, although thermoplastic veils generally have favorable effects on damping ratios of the GF composites, it has been revealed that these veils other than PPS and PI cause deterioration in CF composites. On the other hand, since vibration reduction depends on inherent damping and structural stiffness, this study also examined the storage‐to‐loss modulus ratios which denote the loss factors. In this respect, it was discovered that, while PPS, PEEK, PA, and PI thermoplastic veils included among the GF laminates ascend the loss factors of composites, only PI and PPS thermoplastic veils were shown to be positively effective in CF laminates. Moreover, CF and GF reinforced composites interleaved with thermoplastic veils generally exhibited higher natural frequency and lower damping ratio compared to the entirely CF or GF laminated composites. These results show that composite specimens gained bending stiffness due to local deformation hardening, and improved dynamic properties thanks to thermoplastic veil interleaved was attributed to increased toughness and delamination resistance.

This article reports fabrication of very efficient electromagnetic interference (EMI) shielding composites prepared by melt blending of polyether‐ether ketone (PEEK), multiwalled carbon nanotubes (MWCNTs) covered with polyetherimide (PEI), and ferroferric oxide (Fe 3 O 4 ) nanoparticles as a matrix, dielectric and magnetic loss fillers, respectively. The surface of MWCNTs was modified with PEI to improve their dispersion in the PEEK matrix as well as interfacial adhesion. Fe 3 O 4 nanoparticles were then deposited onto the surface of MWCNTs coated with PEI (MWCNTs@PEI). In this case, MWCNTs@PEI filler served as a carrier for Fe 3 O 4 nanoparticles for their even dispersion in PEEK. Additionally, combination of Fe 3 O 4 nanoparticles and MWCNTs@PEI (Fe 3 O 4 and MWCNTs@PEI) provided the resulting EMI materials with the enhanced electromagnetic absorption ability. This property was then utilized to fabricate PEEK‐based (Fe 3 O 4 and MWCNTs@PEI/PEEK) EMI shielding composites. Specific shielding effectiveness (SSE) of this composite was ~54.4 dB mm −1 in the X band (8.2‐12.4 GHz). Tensile strength and the temperature at 5% weight loss of this novel EMI shielding materials were 117 MPa and 600°C, respectively.

To inform the design of effective mitigation strategies for high performance thermoplastics (HPTPs) we assessed the environmental impacts of three varieties: polyetherimide (PEI) and polyphenylene sulphide (PPS), polybutylene terephthalate (PBT)...

This work demonstrates the feasibility of fabricating containers for the ultimate disposal of spent nuclear reactor fuel and high-level radioactive waste using polymer-based composite materials. The study has identified three engineering polymers suitable for this demanding application: polyetheretherketone (PEEK), polyetherimide (PEI), and polysulfone (PSU). PEEK and PEI are used as composite materials components, with 30% carbon and glass fiber, respectively, whereas PSU is used as a virgin (nonreinforced) material. The rationale for the choice of polymer composites comes from their superior physical, mechanical, and chemical performance, in addition to their economical advantage. In particular, they display better resistance to corrosion and to structural weakening from irradiation.Scaled-down containers were fabricated using these materials. They were subjected to a battery of tests under conditions similar to those expected for the disposal environment of actual radioactive waste–filled containers. In particular, the container models were irradiated in the pool of a SLOWPOKE-2 nuclear research reactor, accumulating doses from a mixed-radiation field that were comparable to total doses accumulated over 500 yr at a deep underground waste repository site. Mechanical compression tests mimicked the large hydrostatic pressures incurred from granite rock at depths of some 1000 m within the Canadian Shield.Several composite materials were tested, and for the three engineering materials listed above, some of the results are as follows:1. variation in elastic modulus following a 28.9-kGy radiation dose—PEEK, −6.66% ± 0.47%; PEI, +5.63% ± 0.23%; PSU, +3.16% ± 0.13%2. compression results for the irradiated container models and load at break and strain—PEEK, 2.152 MPa and 1178 μmm-1; PEI, 1.236 MPa and 1171 μmm-1; PSU, 1.190 MPa and 2576 μmm-1, respectively3. cost analysis—costs for the fabrication of the prototype containers based on PEEK, $273610; PEI, $145920; PSU, $257460.The work also provided insight into potential problems in the fabrication of full-sized containers and into the best fabrication methods to adopt. The method of filament winding would be more appropriate for the PEEK- and the PEI-based composite materials, while blow forming would be the preferred method for the PSU material. In particular, this research could determine the best way to design the container lids.

Review on dissimilar structures joints failure

On the influence of manufacturing parameters on buckling and modal properties of sandwich composite structures