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Carbon fiber reinforced polymers (CFRPs) are increasingly used in the aerospace industry because of their robust mechanical properties and strength to weight ratio. A significant drawback of CFRPs is their resistance to formability when drawing continuous CFRPs into complex shapes as it tends to bridge, resulting in various defects in the final product. However, CFRP made from Stretch Broken Carbon Fiber (SBCF) aims to solve this issue by demonstrating superior formability compared to conventional continuous CFRPs. To study and validate the performance of SBCF, a statistical design of the experiment was conducted using three different types of CFRPs in tow/tape form. Hexcel (Stamford, CT, USA) IM7-G continuous carbon fiber impregnated with Huntsman (The Woodlands, TX, USA) RDM 2019-053 resin system, Hexcel SBCF impregnated with RDM2019-053 resin, and Montana State University manufactured SBCF impregnated with Huntsman RDM 2019-053 resin were tested in a multitude of forming trials and the data were analyzed using a statistical model to evaluate the forming behavior of each fiber type. The results show that for continuous fiber CFRP tows forming, Fmax and Δmax do not show statistical significance based on temperature fluctuations; however, in SBCF CFRP tows forming, Fmax and Δmax is dominated by the temperature and geometry has a low statistical influence on the Fmax. The lower dependence on tool geometry at higher temperatures indicates possibly superior formability of MSU SBCF. Overall findings from this research help define practical testing methods to compare different CFRPs and provide a repeatable approach to creating a statistical model for measuring results from the formability trials. [ABSTRACT FROM AUTHOR]

The main undisputed benefit of using long fibre composite materials, whose properties could be targeted for a particular application, lies in the efficient utilisation of material. Using a method of pre-impregnated fibre winding, a rod with a reinforced middle part was created through the local adjustment of the winding angle in order to increase the local bending stiffness. The aim of our work was to describe, experimentally and subsequently using appropriate numerical models, the behaviour of two composite rods, one with a locally variable winding angle and the other with a constant winding angle. The difference in the mechanical behaviour of both structures was clearly evident during the experiment. By using a suitable composite pre-processor and by choosing some multiple element sets, it was also possible to accurately simulate the real behaviour of such components, which actually have several regions, each with different mechanical parameters. Together with the expected different flexural strength, a traditional three-point bending test also explored the different shape of the resulting deformation in the two compared parts. Differences in the maximum strength and the mode of fi nal deformations were also identified.

Automated tape placement - ATP - is a recent manufacturing technology for composite materials. Therefore, a correct modeling of the multi-physical process is critical in order to make possible in-situ consolidation. In this work, we propose an accurate modelling framework and an efficient simulation procedure of physics occurring during the process with the aim of studying the influence of material and process parameters into the material consolidation evolution. For that purpose, an accurate description of the prepreg surface becomes compulsory, justifying the use of a multi-resolution description of it based on the use of wavelets. [ABSTRACT FROM AUTHOR]

Abstract A thermoplastic-penetrated natural fiber belt was developed for potential application in filament winding. Discontinuous sisal fiber bundles were impregnated with high density polyethylene and then connected into continuous pre-pregs via hot-pressing. The interfacial bonding was improved by treating the fibers with sodium hydroxide (NaOH) and three types of coupling agents (NH 2 C 3 H 6 Si(OC 2 H 5) 3 , C 2 H 3 Si(OC 2 H 5) 3 and C 51 H 112 O 22 P 6 Ti). Tensile properties of the fiber bundles, pre-pregs, and annular specimens were determined. The fiber surface microstructure and the pre-preg interfacial bonding were evaluated via scanning electron microscopy and Fourier transform infrared spectroscopy. Among the four treatments, 2% C 2 H 3 Si(OC 2 H 5) 3 yielded the most significant improvement in the tensile properties of the pre-pregs and annular specimens. The fiber bundle was less damaged by the coupling agents treatment comparing to NaOH treatment. When the overlap at the end of the sisal fibers was >11 mm, the presence of the joint had no effect on the tensile strength of the pre-preg. The pre-preg belt containing treated fibers, which was evaluated based on the requirements of filament winding applications, exhibited a high performance. [ABSTRACT FROM AUTHOR]

The ITER Feeder is an important subsystem, which transmits the electrical power to the ITER Tokamak magnet system. In the Feeder, all the HV potential components, including the current leads, the busbars, and the joints, need to be insulated with solid composite materials to electrically isolate the HV potential from ground. Based on over three years of preliminary qualification and experimental comparison, the prepreg tape and relevant curing techniques were finally chosen as the formal feeder insulation material and method. The formal insulation qualification was launched, including the material qualification and the component qualification. Now the static tensile/shear strength, the fatigue tensile strength, the compression-shear strength, the push-out strength and the void content test for the prepreg material qualification has been completed. This paper describes the whole research improvement of ITER feeder electrical insulation qualification activities, introduces the selection of procured materials and the manufacturing trials, and summarizes the formal qualification items and their test results. [ABSTRACT FROM AUTHOR]

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In situ consolidation of pre-impregnated thermoplastic composite requires as much as possible intimate contact as well as an appropriate molecular diffusion across the interface where the intimate contact takes place. The last depends on the temperature that influences the molecular mobility. Thus, in order to evaluate the consolidation first we must describe accurately the composite surfaces and then, when placed in contact for manufacturing the laminate, a high-resolution simulation of the resulting thermal model must be accomplished to have access to the thermal history at the rough contact surface. In this paper based on a fractal description of the composite surface, the evolution of the intimate contact is performed by solving the flow equations during the compression. High-resolution thermal simulations based on the use of the proper generalized decomposition - PGD - are carried out on the geometrically evolving composite surface. [ABSTRACT FROM AUTHOR]

It is planned that the high voltage electrical insulation on the ITER feeder busbars will consist of interleaved layers of epoxy resin pre-impregnated glass tapes (‘pre-preg’) and polyimide. In addition to its electrical insulation function, the busbar insulation must have adequate mechanical properties to sustain the loads imposed on it during ITER magnet operation. This paper reports an investigation into suitable materials to manufacture the high voltage insulation for the ITER superconducting busbars and pipework. An R&D programme was undertaken in order to identify suitable pre-preg and polyimide materials from a range of suppliers. Pre-preg materials were obtained from 3 suppliers and used with Kapton HN, to make mouldings using the desired insulation architecture. Two main processing routes for pre-pregs have been investigated, namely vacuum bag processing (out of autoclave processing) and processing using a material with a high coefficient of thermal expansion (silicone rubber), to apply the compaction pressure on the insulation. Insulation should have adequate mechanical properties to cope with the stresses induced by the operating environment and a low void content necessary in a high voltage application. The quality of the mouldings was assessed by mechanical testing at 77 K and by the measurement of the void content. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the adhesion properties of phenol formaldehyde-prepreg oil palm veneers that have potential for plywood manufacture. Phenol formaldehyde (PF) resin of three different molecular weights (i.e. 600 (low), 2,000 (medium), and 5,000 (commercial)) were used to pre-treat the veneers. The veneers were soaked in each type of PF resin for 20 seconds, pressed between two rollers, and pre-cured in an oven maintained at 103 ± 2 °C for 24 hours. The volume percent gain (VPG), weight percent gain (WPG), pH, buffering capacity, and contact angle of the phenolic pre-preg veneers were determined. The bonding shear was also evaluated according to British Standard European Norm BS EN 314. The results show that veneers from both inner and outer layers treated with low molecular weight PF (LMwPF) resin had significantly higher VPG and WPG compared to the other PF resins. The pH values of all of the veneers were slightly acidic (6.5 to 6.8) except for those that were treated with commercial molecular weight PF resin (7.8). A buffering capacity study revealed that untreated veneer had a greater resistance toward alkali, but was unstable under acidic conditions, while the phenolic pre-preg veneer behaved differently. This effect was more prominent as the molecular weight of the PF resin increased. An examination of the veneer surfaces demonstrated that phenolic treatment had increased the contact angle of the OPS veneer surfaces significantly. The bonding properties of plywood made from pre-preg palm veneers were found to be superior to those of commercial palm plywood.

Pre-preg material has been widely-used in the industry of the aerospace, the wind power, which has many advantages on manufacture process, and can be chosen as an effective complementary insulation method for the Wet-winding and Vacuum Pressure Impregnation technology in the field of superconducting fusion magnets. ASIPP undertaken many engineering tasks on the superconducting coil and busbar design and manufacture for the large fusion device, the pre-preg material and the relevant curing technology were researched as a new method for the high voltage potential components in ITER Feeders, such as the busbars and current leads. Two types of Chinese industrial glass fiber pre-preg insulation composite material were studied and pre-qualified using vacuum bag and silicone rubber assistance technique in ASIPP. The mechanical properties including the ILSS and UTS at 77 K, and void content of this composites were measured and discussed in this paper in detail. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the adhesion properties of phenol formaldehyde-prepreg oil palm veneers that have potential for plywood manufacture. Phenol formaldehyde (PF) resin of three different molecular weights (i.e. 600 (low), 2,000 (medium), and 5,000 (commercial)) were used to pre-treat the veneers. The veneers were soaked in each type of PF resin for 20 seconds, pressed between two rollers, and pre-cured in an oven maintained at 103 ± 2 °C for 24 hours. The volume percent gain (VPG), weight percent gain (WPG), pH, buffering capacity, and contact angle of the phenolic pre-preg veneers were determined. The bonding shear was also evaluated according to British Standard European Norm BS EN 314. The results show that veneers from both inner and outer layers treated with low molecular weight PF (LMwPF) resin had significantly higher VPG and WPG compared to the other PF resins. The pH values of all of the veneers were slightly acidic (6.5 to 6.8) except for those that were treated with commercial molecular weight PF resin (7.8). A buffering capacity study revealed that untreated veneer had a greater resistance toward alkali, but was unstable under acidic conditions, while the phenolic pre-preg veneer behaved differently. This effect was more prominent as the molecular weight of the PF resin increased. An examination of the veneer surfaces demonstrated that phenolic treatment had increased the contact angle of the OPS veneer surfaces significantly. The bonding properties of plywood made from pre-preg palm veneers were found to be superior to those of commercial palm plywood. [ABSTRACT FROM AUTHOR]

Flexural properties of carbon fibre reinforced plastics (CFRPs) with multi-layer interfacial reinforcement of hierarchically structured aramid pulp (AP) fibres were measured at −40 and −100 °C under three-point bending (3 PB) together with unreinforced CFRPs. After curing, the 'interleaf' thicknesses were 3.3, 5.6 and 12.2 μm for three different AP areal densities of 0.8, 1.6 and 3.2 g/m2, respectively. 3 PB tests of control and AP reinforced CFRPs were also performed at 20 °C to compare the AP strengthening effects and their variations from ambient temperature to −100 °C. The flexural strength increased up to 30.6% at −100 °C for specimens with 1.6 g/m2 AP in comparison to 24.5% enhancement at room temperature. This finding proves that a proper composite design, i.e. adding tough and flexible short fibres into the brittle-fibre and brittle-matrix system, can indeed enhance the structural performance of CFRPs. The small-scale in-house 'pre-preg' fabrication adopted in this study shows that the ultra-thin layers of AP fibres can be potentially incorporated into a large-scale pre-preg production so that the extra step of inserting the interleaving layers can be removed from the composite forming process. In other words, end users can use the AP toughened pre-pregs just like any carbon fibre pre-pregs currently in use without the trouble of interleaving. [ABSTRACT FROM AUTHOR]