Numerical and experimental analyses of resin infusion manufacturing processes of composite materials

Liquid resin infusion (LRI) processes are promising manufacturing routes to produce large, thick, or complex structural parts. They are based on the resin flow induced, across its thickness, by a pressure applied onto a preform/resin stacking. However, both thickness and fiber volume fraction of the final piece are not well controlled since they result from complex mechanisms which drive the transient mechanical equilibrium leading to the final geometrical configuration. In order to optimize both design and manufacturing parameters, but also to monitor the LRI process, an isothermal numerical model has been developed which describes the mechanical interaction between the deformations of the porous medium and the resin flow during infusion.1, 2 With this numerical model, it is possible to investigate the LRI process of classical industrial part shapes. To validate the numerical model, first in 2D, and to improve the knowledge of the LRI process, this study details a comparison between numerical simulations and an experimental study of a plate infusion test carried out by LRI process under industrial conditions. From the numerical prediction, the filling time, the resin mass and the thickness of the preform can be determined. On another hand, the resin flow and the preform response can be monitored by experimental methods during the filling stage. One key issue of this research study is to highlight the changes in major process parameters during the resin infusion stage, such as the temperature of the preform and resin, and the variations of both thickness and fiber volume fraction of the preform. Moreover, this numerical/experimental approach is the best way to improve our knowledge on the resin infusion processes, and finally, to develop simulation tools for the design of advanced composite parts

Monitoring the resin infusion manufacturing process under industrial environment using distributed sensors

A novel direct approach to detect the resin flow front during the Liquid Resin Infusion process under industrial environment is proposed. To detect the resin front accurately and verify the results, which are deduced from indirect micro-thermocouples measurements, optical fiber sensors based on Fresnel reflection are utilized. It is expected that the results derived from both techniques will lead to an improvement of our understanding of the resin flow and in particular prove that micro-thermocouples can be used as sensors as routine technique under our experimental conditions. Moreover, comparisons with numerical simulations are carried out and experimental and simulated mold filling times are successfully compared.Comment: JM-JCM-46.pd

Stabilité dimensionnelle des circuits imprimés multicouches (influence du renfort)

ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Characterization of Liquid Resin Infusion (LRI) filling by fringe pattern projection and in situ thermocouples

International audiencePrepregs are not alone suited to the manufacturing of new types of aircraft structural parts that tend to be thicker and have more complex shapes. Direct processes called Liquid Composites Moulding (LCM), like Resin Transfer Moulding (RTM) or Resin Infusion Process (LRI: Liquid Resin Infusion, RFI: Resin Film Infusion) are now available. Particular attention is paid here to LRI process that looks very promising. In order to optimize both the design and manufacturing parameters in LRI processes, a general model to analyze the isothermal fluid flow through highly compressible porous media such as fibrous preforms has been recently proposed [1], [2] and [3]. To validate the model and to improve the knowledge of the LRI process, an experimental approach is proposed. Two different measurement techniques, micro-thermocouple sensors and fringe projection technique, have been used to characterize the process. It appears that results derived from both techniques are in agreement and support the assumption that the resin flow occurs mainly transversely to the preform plane

Etude numérique et expérimentale de procédé d'élaboration des matériaux composites par infusion de résine (LRI)

Les procédés de fabrication dits LRI (Liquid Resin Infusion) sont prometteurs pour produire des pièces de grandes dimensions ou épaisseur, et des structures complexes, mais ils sont encore difficiles à maîtriser et à contrôler.  Pour optimiser les paramètres importants contrôlant ces procédés, une approche numérique / expérimental spécifique est nécessaire. Les modèles utilisés sont de type fluide-poroelasticité en grande déformation

Chronic stress does not further exacerbate the abnormal psychoneuroendocrine phenotype of Cbg-deficient male mice

Chronic stress leads to a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis which can constitute a base for pathophysiological consequences. Using mice totally deficient in Corticosteroid binding globulin (CBG), we have previously demonstrated the important role of CBG in eliciting an adequate response to an acute stressor. Here, we have studied its role in chronic stress situations. We have submitted Cbg ko and wild-type (WT) male mice to two different chronic stress paradigms - the unpredictable chronic mild stress and the social defeat. Then, their impact on neuroendocrine function - through corticosterone and CBG measurement - and behavioral responses - via anxiety and despair-like behavioral tests - was evaluated. Both chronic stress paradigms increased the display of despair-like behavior in WT mice, while that from Cbg ko mice - which was already high - was not aggravated. We have also found that control and defeated (stressed) Cbg ko mice show no difference in the social interaction test, while defeated WT mice reduce their interaction time when compared to unstressed WT mice. Interestingly, the same pattern was observed for corticosterone levels, where both chronic stress paradigms lowered the corticosterone levels of WT mice, while those from Cbg ko mice remained low and unaltered. Plasma CBG binding capacity remained unaltered in WT mice regardless of the stress paradigm. Through the use of the Cbg ko mice, which only differs genetically from WT mice by the absence of CBG, we demonstrated that CBG is crucial in modulating the effects of stress on plasma corticosterone levels and consequently on behavior. In conclusion, individuals with CBG deficiency, whether genetically or environmentally-induced, are vulnerable to acute stress but do not have their abnormal psychoneuroendocrine phenotype further affected by chronic stress

Transcortin is crucial in HPA axis and despair-like behavior sex difference in mice

International audienc

Rôle de la transcortine (CBG) dans la vulnérabilité individuelle des réponses de stress

National audienc

Genetic variability in metabolic and behavioral responses to Western life style: analysis of the transcortin-deficient mouse after high fat diet and chronic stress

National audienc

Role of corticosteroid binding globulin in emotional reactivity sex differences in mice

Sex differences exist for stress reactivity as well as for the prevalence of depression, which is more frequent in women of reproductive age and often precipitated by stressful events. In animals, the differential effect of stress on male's and female's emotional behavior has been well documented. Crosstalk between the gonadal and stress hormones, in particular between estrogens and glucocorticoids, underlie these sex differences on stress vulnerability. We have previously shown that corticosteroid binding globulin (CBG) deficiency in a mouse model (Cbg k.o.) leads, in males, to an increased despair-like behavior caused by suboptimal corticosterone stress response. Because CBG displays a sexual dimorphism and is regulated by estrogens, we have now investigated whether it plays a role in the sex differences observed for emotional reactivity in mice. By analyzing Cbg k.o. and wild-type (WT) animals of both sexes, we detected sex differences in despair-like behavior in WT mice but not in Cbg k.o. animals. We showed through ovariectomy and estradiol (E2) replacement that E2 levels explain the sex differences found in WT animals. However, the manipulation of E2 levels did not affect the emotional behavior of Cbg k.o. females. As Cbg k.o. males, Cbg k.o. females have markedly reduced corticosterone levels across the circadian cycle and also after stress. Plasma free corticosterone levels in Cbg k.o. mice measured immediately after stress were blunted in both sexes compared to WT mice. A trend for higher mean levels of ACTH in Cbg k.o. mice was found for both sexes. The turnover of a corticosterone bolus was increased in Cbg k.o. Finally, the glucocorticoid-regulated immediate early gene early growth response 1 (Egr1) showed a blunted mRNA expression in the hippocampus of Cbg k.o. mutants while mineralocorticoid and glucocorticoid receptors presented sex differences but equivalent mRNA expression between genotypes. Thus, in our experimental conditions, sex differences for despair-like behavior in WT mice are explained by estrogens levels. Also, in both sexes, the presence of CBG is required to attain optimal glucocorticoid concentrations and normal emotional reactivity, although in females this is apparent only under low E2 concentrations. These findings suggest a complex interaction of CBG and E2 on emotional reactivity in females