Letteratura scientifica selezionata sul tema "Tow-preg"

Abstract New generation non-crimp fabric (NCF) offers an attractive thin and lightweight building block alternative in the design of composite materials and structures. Pre-assembly of multiple plies of parallel fibers, each laying in a different orientation would not require crimping of the fibers and would enable one-axis lay-up that can substantially reduce the labor, scrap, and manufacturing costs. A state-of-the-art tow-spreading technique enables ply thickness to be reduced to as low as one-third of the typical commercial high quality pre-preg ply thickness. The thin-ply NCF stacks result in well-dispersed plies of different fiber orientations and creates the so-called homogenized laminates without ply clustering. As an option, bi-angle thin-ply NCF offers two different fiber orientations with one being off-axis, e.g. at ϕ°, along with an on-axis 0° forming (0/ϕ) assembly. This allows to design in anisotropic properties within the NCF building block. An overview of several aspects of the thin-ply bi-angle NCF composites is provided to address associated benefits and opportunities in the lightweight structural composites design process.

Purpose In this paper, continuous glass tow preg-reinforced acrylonitrile butadiene styrene (ABS) composites were fabricated by using a 3D printing method, and the purpose of this study is the investigation of the fiber preimpregnation effect on the mechanical behavior of these composites. In addition, a simple theoretical approach (mixture law), which considers the elastic behavior of reinforced composites and a numerical simulation method based on finite element method (FEM), was used to predict the tensile stress–strain behavior of ABS/glass tow preg composites in the elastic region. Design/methodology/approach Different groups of preimpregnated glass tows with various ABS amounts (named 2%, 10%, 20% and 30%) were prepared by the solution impregnation method. Then, preimpregnated glass tows (prepregs or tow-pregs) were fed into the printer head along with the polymeric ABS filament to print the composites. The tensile, flexural and short beam tests were conducted to evaluate the mechanical properties of the printed composites. Findings The first result of using tow-pregs instead of dry tows in continuous fiber 3D printing is much easier printing, printability improvement and the possibility of printing layers with low thickness, which can further increase the mechanical properties. The mechanical test results showed all of the glass prepregs improve strength and modulus in the tensile, three-point bending and short beam tests compared with neat ABS specimens, but statistical analysis showed that ABS weight percentage in the prepregs had no significant effect on the mechanical strength of composites except for the tensile modulus. Samples containing 2%-prepreg (minimum ABS amount in the tow-pregs) showed a significant improvement in tensile modulus. In the simulation section, good agreement is obtained between the model predictions and experimental tensile results. The results show that an acceptable deviation (14%) exists between the experimental and predicted value of elastic modulus by the numerical model. Originality/value To the best of the authors’ knowledge, this is the first study showing the effects of ABS weight percentage in prepregs on the mechanical properties of 3D printed continuous fiber-reinforced composites and predicting the mechanical behavior of 3D printed composites by numerical simulation method.

L’introduction de composites à matrice céramique (CMC) oxyde/oxyde est envisagée dans les turbomachines de nouvelle génération. Les principaux freins à l’industrialisation de ces matériaux sont la diversité des procédés d’élaboration, leurs coûts, ainsi que l’hétérogénéité des microstructures et des propriétés mécaniques. Ces travaux de thèse en collaboration entre l’Onera, l’IRT Saint-Éxupéry et l’ICA étudient une nouvelle voie d’élaboration de CMC alumine/alumine, par une étape d’imprégnation de mèche en continu. Pour commencer, une étude de formulation de suspensions aqueuses d’alumine compatibles avec l’élaboration de composites par le procédé d’imprégnation en ligne suivi d’une mise en forme en autoclave et d’un frittage a été menée. Deux plastifiants organiques hygroscopiques, le sorbitol et le glycérol, ainsi qu’un gélifiant, la boehmite, ont été évalués. Les cycles thermiques en autoclave ont été adaptés à la composition des suspensions et en particulier aux additifs organiques. Plusieurs compositions de suspensions ont été retenues et les microstructures des CMC résultants ont été caractérisées. Les relations composition de la suspension – adaptabilité au procédé – microstructure du composite ont été investiguées. Enfin, les comportements mécaniques à température ambiante des différentes nuances de CMC ont été examinés en lien avec leurs microstructures, et des scénarios d’endommagement en traction ont été proposés
The use of oxide/oxide ceramic matrix composites (CMCs) is being considered for new generation engines. The main obstacle to the industrialisation of these materials are the diversity of production processes, their costs, and the heterogeneity of the microstructures and mechanical properties. This thesis is a collaboration between Onera, IRT Saint-Éxupéry and ICA. It investigates a new way of producing alumina/alumina CMC by using a continuous tow impregnation process. Firstly, a study was carried out into the formulation of aqueous alumina slurries compatible with the production of composites using a continuous tow impregnation line, followed by autoclave shaping and sintering. Two hygroscopic organic plasticisers, sorbitol and glycerol, as well as a gelling agent, boehmite, were evaluated. Autoclave thermal cycles were adapted to slurries compositions, with particular regard to the organic additives. Several compositions were selected and the microstructures of the resulting CMCs were characterised. The relationships between slurry composition, process adaptability and composite microstructure were investigated. Finally, the mechanical behaviour at ambient temperature of the different CMC grades were examined in relation to their microstructures, and tensile damage scenarios were proposed

Abstract This chapter discusses the ways in which the evolution of filament winding software systems has capitalized on the inherent flexibility of computer numerical controlled winding machines and enhanced their productivity. It provides a detailed discussion on different types of geometries that can be wound, from the simple to the highly complex, with insight into the limitations, advantages, and challenges of each. Components covered include classic axisymmetric parts (rings, pipes, driveshafts, pipe reducers, tapered shafts, closed-end pressure vessels, and storage tanks), nonround sections (aeromasts, airfoils, box sections, and fuselage sections), curved-axis parts (elbows, ducts), and special applications (tees). Basic winding concepts, such as band pattern, are discussed and explained, and some simple predictive formulae are introduced. The chapter also provides examples of programming various geometries using advanced software tools and discusses how various materials, such as rovings, tow-preg, prepreg tape, and woven materials, affect winding program generation.

Abstract Carbon fiber Thermoplastic pre-preg tape laydown and consolidation used with Automated Fiber Placement (AFP) required high temperatures to melt the matrix. There are a few methods that can reach the desired temperature. Hot-gas torch, laser heating, and arc-flash lamp-based heating systems are the most popular among them. Among the three, arc-flash lamp-based heating provides the most versatility regarding heating range and controllability. The lamp pulses light of high radiation intensity to heat the tow and substrate material during laydown rapidly. The irradiance output by the lamp is controlled by three process parameters, namely, (1) pulse width, (2) pulsing frequency, and (3) voltage. Further control can be achieved by changing the distance between the flash lamp and the tows. Therefore, the irradiance output from the lamp can be widely varied by changing the process and geometric parameters. This study aims to characterize the irradiance output from a xenon arc-flash heating system and its control parameters. The Xenon flash lamp’s irradiance response was used to map the irradiance profile on the tow and substrate within an Automated Fiber Placement machine. The impact of the AFP control parameters like roller compaction, tow layup speed, and positioning of xenon flash lamp on the irradiance profile of the tow and substrate were also examined in this study.