Search results for "Mécanique des matériaux"
showing 10 items of 11 documents
Quasi-static behaviour and damage assessment of flax/epoxy composites
2015
Experimental investigations were conducted on flax and E-glass fibres reinforced epoxy matrix composites subjected to quasi-static loadings. Flax/epoxy samples having [0]12, [90]12, [0/90]3S and [±45]3S stacking sequences, with a fibre volume fraction of 43% have been tested under tension, compression and in-plane shear loadings. Overall, the compression strength of glass/epoxy was 76% greater than for the flax/epoxy composite. The damage evolution of flax/epoxy of [0/90]3S and [±45]3S samples has been evaluated in terms of transverse crack densities with respect to the load increment. The crack density exhibited a classical “S” shaped pattern for [0/90]3S and linearly for [±45]3S specimens…
Fibre extraction from oleaginous flax for technical textile applications: influence of pre-processing parameters on fibre extraction yield, size dist…
2017
International audience; Cultivated primarily for its seeds, oleaginous flax could also be valued for the different fractions that can be extracted from the straw. However, as the straws are not harvested with the same technique and care than for the textile flax, the classical scutching technique cannot be used. As a consequence, an “all fibre” device was used to perform the separation of the different constituents of the oleaginous flax straws. The different fractions were quantified for two retting levels and for two degrees of rewetting of the stems. The physical and mechanical properties of fibres were then evaluated. It appears that the relative amount of fibres extracted from oleagino…
Springback of thick sheet AHSS subject to bending under tension
2012
Lien vers la version éditeur : http://www.sciencedirect.com/science/article/pii/S0020740312000677 The springback behavior of four advanced high-strength sheet steels (Dual-Phase, TRIP, ferrite-bainite) with thicknesses ranging from 1.2 to 4 mm was investigated by means of the bending-under-tension (BUT) test. The applicability of several guidelines from the literature was investigated experimentally and numerically. The monotonic decrease of springback as back force increased was confirmed for this category of sheet steels, and a general trend for the non-linear influence of the tool radius was observed. The influence of numerical factors on the predicted values of springback was investigat…
Investigation of thick sheet AHSS springback in combined bending under tension
2012
In this paper, we investigate the springback behavior of several advanced high-strength sheet steels (TRIP, Dual-Phase, ferrite-bainite) with thicknesses up to 4 mm. Samples were tested by means of the bending-under-tension (BUT) test. The BUT has been extensively applied, in the literature, to relatively thin (1 mm and thinner) sheet metals for automotive applications; the applicability of several guidelines from the literature was investigated in this work in the context of thick advanced high strength steel (AHSS) sheets and using a sample width of 12 mm. The monotonic decrease of springback as back force increased was confirmed for this category of sheet steels, and a general trend for …
Impact behaviour of flax/epoxy composite plates
2015
This paper presents an experimental investigation of the impact behaviour of flax/epoxy composite plates submitted to low-velocity transverse impact. Low energy drop-weight impact tests have been performed on two types of quasi-isotropic flax/epoxy composites, rectangularly shaped with edges lengths of 142 mm × 94 mm and 2.85 mm thick. Residual properties have been assessed by compression after impact tests. A detailed description of damage development, especially the increase of the rear face crack with respect to the impact energy is given by the microscopic observation. The influence of impact damage on the residual strength is described. A loss of 15%–30% in compression resistance was n…
A comparative study of fatigue behaviour of flax/epoxy and glass/epoxy composites
2012
Experimental investigations on flax and glass fabrics reinforced epoxy specimens, i.e. FFRE and GFRE, submitted to fatigue tests are presented in this paper. Samples having [0/90]3S and [±45]3S stacking sequences, with similar fibre volume fractions have been tested under tension–tension fatigue loading. The specific stress-number of cycles to failure (S–N) curves, show that for the [0/90]3S specimens, FFRE have lower fatigue endurance than GFRE, but the [±45]3S FFRE specimens offer better specific fatigue endurance than similar GFRE, in the studied life range (<2 × 10^6). Overall, the three-stage stiffness degradation is observed in all cases except for [0/90]3S FFRE specimens, which prese…
Properties evolution of flax/epoxy composites under fatigue loading
2014
International audience; The tension-tension fatigue behaviour of flax fibre reinforced epoxy matrix composites have been investigated for specimens having [0]12, [90]12, [0/90]3S and [±45]3S lay-ups. The Probabilized Stress-Number of cycles (P-S-N) curves have been determined for each laminate type. The measured stress and strain data allowed to quantify the evolution of the mechanical properties, i.e. stiffness, damping and permanent strain as a function of imposed cycles. Especially, the stiffening phenomenon of flax reinforcements oriented parallel to the loading direction has been confirmed. However, due to the competition between damage development and the fibre stiffening, the increas…
Analysis of laser shock waves and resulting surface deformations in an Al-Cu-Li aluminium alloy
2012
Abstract Laser shock processing is now a recognized surface treatment for improving fatigue or corrosion behaviour of metallic materials through the generation of a compressive stress field. In turn, the analysis of shock wave propagation is of primary importance to predict numerically morphological and mechanical surface modifications. Considering experimental and numerical analyses of shock wave propagation, and surface deformations induced by single impacts, a 2050 aluminum alloy having different microstructures was investigated under laser-shock loading. In a first step, the evolution of shock wave attenuation and elastic precursor amplitude was correctly reproduced by finite element si…
A physical-based constitutive model for surface integrity prediction in machining of OFHC copper
2017
International audience; Due to the rising interest in predicting machined surface integrity and sustainability, various models for metal cutting simulation have been developed. However, their accuracy depends deeply on the physical description of the machining process. This study aims to develop an orthogonal cutting model for surface integrity prediction, which includes a physical-based constitutive model of Oxygen Free High Conductivity (OFHC) copper. This constitutive model incorporates the effects of the state of stress and microstructure on the work material behavior, as well as a dislocation density-based model for surface integrity prediction. The coefficients of the constitutive mod…
Influence of cutting process mechanics on surface integrity and electrochemical behavior of OFHC copper
2014
The authors gratefully acknowledge the support received from IC ARTS and CEA Valduc; International audience; Superfinishing machining has a particular impact on cutting mechanics, surface integrity and local electrochemical behavior. In fact, material removal during this process induces geometrical, mechanical and micro-structural modifications in the machined surface and sub-surface. However, a conventional 3D cutting process is still complex to study in terms of analytical/numerical modeling and experimental process monitoring. So, researchers are wondering if a less intricate configuration such as orthogonal cutting would be able to provide information about surface integrity as close as…