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| Registros recuperados: 14 | |
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| Humeau, Corentin; Davies, Peter; Le Gac, Pierre Yves; Jacquemin, Frédéric. |
| Polyamide fibres are known to be sensitive to water, and this has limited their marine applications. However, their low stiffness and high strength could be attractive for shallow water mooring line ropes, particularly for floating wind turbines. Such applications require the influence of water on mechanical behaviour to be fully understood, and this paper presents results describing how water affects static and creep response of polyamide 6 fibre yarns. First, the effect of water on fibre Tg is quantified, then tensile behaviour is examined. Finally, a model based on Schapery’s non-linear creep analysis is identified for different humidity conditions. The results show that while moisture has a small effect on short-term tensile behaviour, long term... |
| Tipo: Text |
Palavras-chave: Aging; Moisture; Fibre; Creep; Viscoelastic model. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00460/57190/59251.pdf |
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| Le Guen-geffroy, Antoine; Le Gac, Pierre Yves; Habert, B.; Davies, Peter. |
| This paper shows how physical ageing and plasticization processes are coupled in an amine-based epoxy. The study combines several ageing conditions including thermal ageing in the dry state (from 40 to 60 °C), ageing in a humid environment (RH 50% and RH 75%) as well as immersion in seawater at several temperatures from 15 to 40 °C. First results are presented to highlight that the two processes (physical ageing and plasticization) both occur when the epoxy is immersed in water. A step-by-step approach is then used to evaluate how the plasticization process induced by the presence of water is affected by physical ageing and vice versa. It appears that the plasticization process, which leads to a large decrease in maximum stress under tensile loading, is... |
| Tipo: Text |
Palavras-chave: Epoxy; Physical ageing; Water; Plasticization. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00512/62319/66717.pdf |
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| Huang, Jing; Derue, Isabelle; Le Gac, Pierre Yves; Richaud, Emmanuel. |
| This paper describes water absorption in polydicyclopentadiene (PDCPD) and more specially the impact of thermal oxidation on its behavior. Unaged PDCPD is found to be almost hydrophobic consistently with its non-polar structure. During thermal oxidation, hydrophilicity progressively increases with ageing time. This increase is linked with the buildup of polar products (mainly ketones, carboxylic acids, hydroperoxides, alcohols). Moreover, it appears that water absorption in PDCPD obeys to Flory Huggins law for all conditions considered here. In the meantime, water diffusivity seems to decrease when oxidation level increases. Finally, a mastercurve that links carbonyl concentration, water diffusivity and water-polymer interaction parameter is proposed and... |
| Tipo: Text |
Palavras-chave: Polydicycopentadiene; Water absorption; Thermal oxidation. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00633/74466/74293.pdf |
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| Le Gac, Pierre Yves; Albouy, Pierre-antoine; Sotta, Paul. |
| It is shown in the present paper how the addition of a moderate amount of carbon black filler to a polychloroprene gum modifies the local strain state and alters the ability of the polymer to strain-crystallize. The study combines mechanical and X-ray diffraction performed during classical mechanical cycling and tensile impact tests. It highlights the fact that the strain modification induced by the filler addition is highly inhomogeneous: the crystallization behavior and the local draw ratio state are affected differently. The partial relaxation of the amorphous fraction by the strain-induced crystallization peviously evidenced in the pure gum is still present and should play a protective role. The effect of temperature on the crystallization correlates... |
| Tipo: Text |
Palavras-chave: Polychloroprene; Strain-induced crystallization; X-ray. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00488/60003/63239.pdf |
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| Broudin, Morgane; Marco, Yann; Le Saux, Vincent; Charrier, Pierre; Hervouet, Wilfried; Le Gac, Pierre Yves. |
| Elastomeric parts found in automotive anti-vibration systems are usually massive. Ageing therefore leads to heterogeneous properties, usually induced by several mechanisms due to the availability, or not, of oxygen in the part’s bulk. To better understand the effects of oxygen in the degradation process and on the fatigue properties, this paper aims at studying the ageing of a rubber material (semi-efficient vulcanization system) in aerobic (with oxygen) and anaerobic (without oxygen) conditions for a wide range of temperatures, relevant for under hood applications. The material studied here is a fully formulated compound NR/IR blend reinforced with carbon black. A specific protocol to perform ageing under anaerobic conditions was set up and validated.... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00479/59092/61730.pdf |
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| Le Gac, Pierre Yves; Roux, Gerard; Verdu, Jacques; Davies, Peter; Fayolle, Bruno. |
| Thermal oxidation in air at atmospheric pressure, in the 80-140°C temperature range and in oxygen at 100°C in the 0.02-3 MPa pressure range, of unvulcanized, unstabilized, unfilled polychloroprene (CR) has been characterized using FTIR and chlorine concentration measurement. The kinetic analysis was focused on double bond consumption. A mechanistic scheme involving unimolecular and bimolecular hydroperoxide decomposition, oxygen addition to alkyl radicals, hydrogen abstraction on allylic methylenes, alkyl and peroxyl additions to double bonds and terminations involving alkyl and peroxy radicals was elaborated. The corresponding rate constants were partly extracted from the literature and partly determined from experimental data using the kinetic model... |
| Tipo: Text |
Palavras-chave: Polychloroprene; Oxidation; Radical chain; Kinetics. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00199/31010/29413.pdf |
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| Huang, Jing; Minne, Wendy; Drozdzak, Renata; Recher, Gilles; Le Gac, Pierre Yves; Richaud, Emmanuel. |
| Thin unstabilized PDCPD film were thermally oxidized in ovens at several temperatures ranging from 50 °C to 120 °C. Hydroperoxide concentration was monitored by DSC. It was observed that hydroperoxides concentration reaches a plateau with short induction times, for example around 8 h at 50 °C. This plateau occurs at very high concentration, around about 1 mol l−1 at 50 °C. In order to study both the chemical mechanisms and the kinetics of hydroperoxides decomposition, oxidized samples were thermally aged in an inert atmosphere to destroy hydroperoxides. For initially high concentrations corresponding to the “plateau”, it was shown that hydroperoxides decompose following a bimolecular process, the rate constant of which being calculated from the... |
| Tipo: Text |
Palavras-chave: Polydicyclopentadiene; Thermal oxidation; Hydroperoxide decomposition; Polymerization catalysts. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00609/72080/70798.pdf |
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| Davies, Peter; Arhant, Mael; Le Gac, Pierre Yves; Le Gall, Maelenn; Kemlin, Guillaume. |
| There are more than a thousand species of bamboo and some of these contain large amounts of fibres with attractive properties. However, the extraction of the fibres without damaging them is difficult, requiring energy and special equipment. One solution is to use the bamboo in the form of thin strips taken from fibre-rich regions of the plant, as done by the Cobratex company in an innovative process. These contain the fibres but they are protected from damage and keep their alignment. This paper presents the results from a study of bamboo strips, alone and in an infused composite. The influence of seawater immersion is investigated. The composite weight gain is high, around 25 %, but most of the water is in the natural canals of the wood. The influence of... |
| Tipo: Text |
Palavras-chave: Bamboo; Density; Mechanical properties; Wet aging. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00593/70534/68681.pdf |
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| Le Gac, Pierre Yves; Fayolle, Bruno. |
| This study deals with the durability of composites based on polyamide 6.6 (PA6.6) in a humid environment, and more especially, with the loss of fracture properties. It is known that PA6.6 undergoes plasticization in the presence of water, but hydrolysis also occurs. This hydrolysis leads to a sharp decline in fracture properties in resin. The aim of this study is thus to understand the behavior of two PA6.6-based composites, one containing short glass fibers and the other both glass fibers and a rubber. The results showed the transition from ductile to brittle behavior as a function of hydrolysis time in resin. For composites, the drop in elongation breaking with the macromolecular chain length was linear for all ageing conditions considered here without... |
| Tipo: Text |
Palavras-chave: Polyamide 6.6; Hydrolysis; Fracture; Embrittlement; Reinforced plastics. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56197/57755.pdf |
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| Richaud, Emmanuel; Huang, Jing; Le Gac, Pierre Yves. |
| This paper addresses the lifetime prediction of polydicyclopentadiene submitted to thermal oxidation, using a multiscale approach. The chemical changes monitored by FTIR revealed the depletion in double bonds and the appearance of carbonyls. Such molecular changes result in the drop of mechanical properties. A kinetic model was implemented to predict the degradation rate depending on external conditions (temperature, oxygen concentration). This model can be completed to take into account the effect of antioxidants (delaying the thermal degradation) and the oxygen diffusion effects (heterogenous degradation) so as to get closer of real cases. |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00644/75621/76539.pdf |
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| Le Guen-geffroy, Antoine; Davies, Peter; Le Gac, Pierre Yves; Habert, Bertrand. |
| Carbon fiber reinforced composite materials are finding new applications in highly loaded marine structures such as tidal turbine blades and marine propellers. Such applications require long-term damage resistance while being subjected to continuous seawater immersion. However, few data exist on which to base material selection and design. This paper provides a set of results from interlaminar fracture tests on specimens before and after seawater ageing. The focus is on delamination as this is the main failure mechanism for laminated composites under out-of-plane loading. Results show that there are two contributions to changes in fracture toughness during an accelerated wet ageing program: effects due to water and effects due to physical ageing. These are... |
| Tipo: Text |
Palavras-chave: Composite; Delamination; Seawater; Immersion; Ageing. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00652/76410/77458.pdf |
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| Bardin, Antoine; Le Gac, Pierre Yves; Cérantola, Stéphane; Simon, Gaelle; Bindi, Hervé; Fayolle, B.. |
| A hydrolytic kinetic model predicting chains scissions of a polyurethane elastomer (TPU) containing an anti-hydrolysis agent (stabilization via carbodiimide) was developed. This model is based on four components: uncatalysed hydrolysis, acid-catalysed hydrolysis, carboxylic acid dissociation and competitive carbodiimide-based deactivation of acid. Protons were considered as the key catalyst responsible for the hydrolysis. Model parameters were determined by fitting experimental data measured on unstabilized and stabilized TPUs, aged in immersion from 40 to 90 °C. Scission kinetics were predicted for immersion and 50% relative humidity conditions, from 10 to 100 °C. Structure-failure property relationships were also investigated, between molar mass and... |
| Tipo: Text |
Palavras-chave: Thermoplastic elastomer; Hydrolysis; Kinetic model; Structure-property relationships. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00588/70044/67978.pdf |
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| Registros recuperados: 14 | |
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