Crushing and intrusion resistance improvement of aluminum beams by carbon/epoxy composite patches

This study investigates the intrusion and crushing performance of hybrid fiber metal laminates based on aluminum and carbon fiber reinforced polymers, in comparison to reference aluminum parts, made from AA6451 or AA7075 automotive grade alloys. A first set of crushing tests and intrusion tests were performed to assess the influence of several parameters: aluminum thickness (0.9, 1.5 and 2.5 mm) and aluminum composition (AA6451 and AA7075), the thickness of carbon composite patch (2 or 3) and the area of composite coverage, patch or strips. Intrusion test results of hybrid structures were correlated to validate and refine a Finite Element Model. Then, a range of configurations was numerically modelled to determine the optimum aluminum-composite layup architectures and the ideal locations of the patches leading to the best absorbed energy/weight ratio for a given load. Results demonstrate that localized composite patches improve the intrusion properties of tubes without penalizing the overall part weight.

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Baris Çaglar, Jonathan Friedli, Yann Albert Gérard Lebaupin, Véronique Michaud, Mathieu Piccand
ELSEVIER SCI LTD, 2019
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https://infoscience.epfl.ch/record/271143?ln=fr

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Aluminium

L'aluminium est l'élément chimique de numéro atomique 13, de symbole Al. Il appartient au groupe 13 du tableau périodique ainsi qu'à la famille des métaux pauvres. Le corps simple aluminium est un

Matériau composite

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Polymère renforcé de fibres de carbone

Le polymère renforcé de fibres de carbone, ou PRFC (en anglais Carbon Fiber Reinforced Polymer ou CFRP), est un matériau composite très résistant et léger. Son prix reste à l' assez élevé. De la même

Flexural strength of micron-scale plate-like silicon in aluminum

Marta Fornabaio, Andreas Mortensen, Martin Guillermo Mueller, Goran Zagar

Mechanical properties of composite materials and alloys are strongly influenced by the intrinsic mechanical properties of the reinforcing phases they contain; however, due to the irregular shape and small size of particulate reinforcements, measuring their intrinsic properties is a substantial methodological challenge. Here we present a method with which we probe the local flexural strength of individual microscopic plate-like silicon particles, which constitute, together with aluminium, the eutectic microconstituent in AlSi alloys. Silicon particles are extracted from the cast and heat-treated alloy by deep-etching the aluminium matrix. The plates are then are dispersed on a steel substrate, where irregular plate- like particles rest lying on one of their large flat facets. A beam of well-defined dimensions is micro-machined out of individual particles using focused ion beam (FIB) milling perpendicular to the substrate. In this way, the particle surface which is in contact with the substrate and that will later on be subjected to tension upon beam bending, i.e. where strength will be measured, is not affected by the FIB nor by redeposition. The FIB is also used to produce a hole in the steel substrate nearby the micro-machined beam so that the silicon beam can be transported and placed on top of the hole using a micromanipulator. The beam is tested in 3- or 4-point bending until fracture by applying a force with a nanoindenter equipped with a diamond tip featuring one or two small rounded ridges that are longer than the width of the beam. Fractography is carried out after testing to locate and characterize the fracture initiation point. Test results are coupled with Finite Element simulations for interpretation. Error in the measurement, including the influence of possible misalignments, of the measured strength is evaluated.

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Origami-inspired carbon fiber-reinforced composite sandwich materials - Fabrication and mechanical behavior

Yuntong Du, Thomas Keller

A folding fabrication method inspired by origami for carbon fiber-reinforced composites to fabricate three-dimensional structures is presented. PMI foams serve as substrates, making it possible to manufacture this kind of origami-inspired composite sandwich materials in a single-step process. Analytical models are proposed to provide upper and lower bounds of the out-of-plane compressive strength of the origami-inspired composite sandwich materials. Finite element analysis (FEA) and experiments are conducted to characterize the compressive behaviors including the deformation history, failure mode, strength, etc., and verify the validity of the analytical models. By incorporating PMI foams, the out-of-plane compressive failure mode of the composite sandwich material at low relative density changes from buckling to wrinkling or crushing, thus greatly increasing the strength. Additionally, the energy absorption capacity is significantly enhanced due to the PMI foams and their interaction with the composite origami core. This work creates a new method to fold composites into lightweight sandwich materials with high strength and high energy absorption, paving the way for their applications in transport, energy and communication.

ELSEVIER SCI LTD2021

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FE analysis and experimental validation of mechanical wedge-barrel anchors for CFRP rods

Elyas Ghafoori, Hossein Heydarinouri, Alain Nussbaumer

This paper presents a comparative study of the geometrical optimization of mechanical wedge-barrel anchors for prestressed carbon fiber-reinforced polymer (CFRP) rods. Various anchor configurations were simulated using three-dimensional finite-element (FE) models. The FE models were validated using the draw-ins of the wedges, which were measured in static tensile tests. The configurations consisted of a steel barrel and aluminum wedges, taking advantage of the previous anchors. The conical profile of the wedge and barrel in different configurations had either a curve or a constant differential angle. In addition, a series of geometric modifications were introduced to the wedge at the loading using a fillet or cut. The stress concentration on the CFRP rod was evaluated using failure index Fs in the Tsai-Wu failure criterion for composite materials. The results of the FE simulations showed that a greater differential angle resulted in a smaller stress concentration at the loading end of the anchor and the modifications led to a reduction in the stress concentration. In addition, the anchor with a curved profile was selected as the optimal design because it had the smallest stress concentration owing to the smooth transition of the differential angle distribution along the wedge profile.

ELSEVIER SCI LTD2021

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