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Human embryo culture under 2–8% O2 is recommended by ESHRE revised guidelines for good practices in IVF labs. Nevertheless, notably due to the higher costs of embryo culture under hypoxia, some laboratories perform embryo culture under atmospheric O2 tension (around 20%). Furthermore, recent meta-analyses concluded with low evidence to a superiority of hypoxia on IVF/ICSI outcomes. Interestingly, a study on mice embryos suggested that oxidative stress (OS) might only have an adverse impact on embryos at cleavage stage. Hence, we aimed to demonstrate for the first time in human embryos that OS has a negative impact only at cleavage stage and that sequential culture conditions (5% O2 from Day 0 to Day 2/3, then «conventional» conditions at 20% O2 until blastocyst stage) might be a valuable option for human embryo culture. 773 IVF/ICSI cycles were included in this randomized clinical trial from January 2016 to April 2018. At Day 0 (D0), patients were randomized using a 1:2 allocation ratio between group A (20% O2; n = 265) and group B (5% O2; n = 508). Extended culture (EC) was performed when ≥ 5 Day 2-good-quality-embryos were available (n = 88 in group A (20% O2)). In subgroup B, 195 EC cycles were randomized again at Day 2 (using 1:1 ratio) into groups B’ (5% O2 until Day 6 (n = 101)) or C (switch to 20% O2 from Day 2 to Day 6 (n = 94). Fertilization rate, cleavage-stage quality Day 2-top-quality-embryo (D2-TQE), blastocyst quality (Day 5-top-quality-blastocyst (D5-TQB) and implantation rate (IR) were compared between groups A and B (= cleavage-stage analysis), or A(20% O2), B’(5% O2) and C(5%-to-20% O2). Overall, characteristics were similar between groups A and B. Significantly higher rates of early-cleaved embryos, top-quality and good-quality embryos on Day 2 were obtained in group B compared to group A (P P 2 from Day 0 to Day 6 (group A) resulted in significantly lower Day 5-TQB number and rates (P P = 0.45). At Day 6, TQB numbers and rates were also significantly higher in groups B’ and C compared to group A (P P

IF=3.85; International audience; Needed to simulate the behaviour of industrial components through finite element analysis, a continuum damage model formulation for fabric reinforced polymers is provided. Based on the Onera Damage Microstructure Model, it considers the influence of privileged direction of intralaminar matrix damage on the stiffness. In this work, the stored strains are considered as representative of the position of the crack lips. Thus, after calculation of the stresses applied to the crack lips, a friction law has been newly implemented in order to represent the hysteresis loops during cyclic loading. Moreover, the possibility of a shear locking, very common among the textile simulations for large shearing, is introduced with its effect on the matrix damage. The present model is applied to simulate various fabric preforms (woven or non-crimp) under cyclic in-plane shear. Because of similarities of the physical phenomena which occur in each investigated materials, the present model is able to represent a realistic behaviour for every preforms investigated.

IF=2.371; International audience; Short-flax-fibre-composite materials are appealing for technical applications thanks to renewability, biodegradability but also potentially high ratio rigidity/density of flax fibres, in particular. However, the significant variability of technical flax fibres’ constitutive, geometrical and mechanical properties and especially lack of quantitative knowledge about its real impact on composite behaviour still prevent a widespread use of such composites. To overcome this obstacle, this study gives qualitative and quantitative information about impact of variability of flax fibre properties on numerically assessed tensile behaviour of short-flax-fibre-reinforced polypropylene, with particular attention paid to the determination of lower bound of composite behaviour. Different fibre contents and orientations, including in-plane random and distributed orientations, are considered. Results reveal that range of variation of composite behaviour strongly depends on weight of fibre contribution to composite response. It is therefore directly related to fibre content and orientation but also indirectly to manufacturing process, since this latter governs fibre orientation.

IF=2.035; International audience; Mechanical behaviour of short-fibre reinforced composites (SFRC) can be affected by numerous damage phenomena. This paper focuses on the modelling of fibre/matrix debonding initiated at fibre tips, which is the dominant damage mechanism when a majority of short-fibres are subjected to local tensile loadings. A failure criterion for SFRC is proposed based on a critical amount of voids located in debonded areas. Very accurate mechanical states at break can be predicted for SFRC with complex fibre distribution of orientation, for different kinds of uniaxial and biaxial tensile loadings.

International audience; Crashworthiness performance of automotives by introducing new materials is of high interest based on the global mass’ reduction of cars. Bonded techniques are tested at present with respect to the reduction of the mass/energy’s ratio combined with recycling processes. In this study, a compression test program is performed on a bulk structural adhesive under a very large range of strain rates, thus [0.1; 5000]/s. Uniaxial compression tests at 0.1 and 50/s are achieved using a high-speed hydraulic testing machine. A split Hopkinson bar’ device made of PA66 is experimented so as to characterize soft materials in the upper domain of strain rates, thus [500; 5000]/s. A special mold is used for the preparation of the adhesive plates. Two sheets are prepared (thickness 4 mm with 1 MPa pressure and 6 mm with 4 MPa pressure) in order to consider the effect of the pressure during the curing process. Water jet technique is used to extract cylindrical samples from the plates with accurate dimensions. The identification of the compression behaviour of the structural adhesive is lead with objective to find material parameters of a modified G’sell model for finite element modeling of crashworthiness.

IF=2.01; International audience; A specific damage characterization method using Digital Image Correlation for semi-crystalline polymers is proposed for a wide range of strain rates. This damage measurement is an extension of the SEĖ method [16] which was developed to characterize the behaviour laws at constant strain rates of polymeric materials. This procedure is compared to the well-known damage characterization by loss of stiffness technique under quasi-static loading. In addition, an in-situ tensile test, carried out in a microtomograph, is used to observe the cavitation phenomenon in real time. The different ways used to evaluate the damage evolution are compared and the proposed technique is also suitable for measuring the ductile damage observed in semi-crystalline polymers under dynamic loading.

International audience; Epoxy resins are widely used in Carbon Fiber Reinforced Polymers (CFRPs) for the aeronautical industry. They must ensure cohesion in most of the structural composite parts incorporated into the modern manufactured aircrafts. So fracture properties of epoxy resins are essential features to resist critical decohesions in case of impact. Surprisingly however, there are few experimental studies dedicated to the dynamic fracture of these thermoset polymers. Therefore, this research aims at developing an experimental procedure to characterize the dynamic fracture toughness of epoxy resins during propagation. Since glassy polymers exhibit viscous fracture, the crack speed å is known for influencing the toughness of these materials. Then a strain gage method is proposed to determine the mode I dynamic energy release rate G ID for various crack speeds å. Thus an experimental set-up is defined to simultaneously implement strain gage measurement and high speed cinematography. Finally, preliminary results are briefly reported to demonstrate the method validity.

International audience; The purpose of this paper is to propose a simplified macroscopic three-dimensional cohesive element dedicated to crash engineering. At the boundary between the CCZM (Continuous Cohesive Zone Method) and the DCZM (Discrete Cohesive Zone Method) approaches, this cohesive element includes an improved constitutive model in order to take into account the viscoplaticity of the adhesive, its different behaviour in tension and compression but also its damage and failure. After presenting the model used, we will detail how to implement the new macroscopic element in the explicit time loop calculation. An example will illustrate and justify the development of such a cohesive element under dynamic loading.

International audience