Dynamic crushing of wood-based sandwich composite tubes

The article presents the results of dynamic crushing of sandwich tubes that had skins made of carbon or glass fibers – with epoxy resin – and an I214 poplar ply core. By increasing the number of poplar plies from two to six, the absorbed energy is doubled, showing the significant contribution of the wood. The Specific Energy Absorption of sandwiches with carbon fiber skins oscillated between 49.4 J/g and 60 J/g while that with glass fiber skins varied from 35.4 to 43.3 J/g

On the crashworthiness properties of plywood.

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Static and dynamic crushing of sandwich tubes with a birch core and carbon skins

International audienceThis paper presents the results of static and dynamic crushing of wood sandwich tubes made with a birch core and carbon woven skins. 3 tubes (external diameter 64 mm, length 120 mm) were crushed in static and 3 others in dynamic under a drop tower. The results reveal very interesting energy absorption performance of such structures. The Specific Energy Absorption is 50.4 J/g in static and 66.6 J/g in dynamic, the energy absorbed is 5427 J in static and 7045 J in dynamic (170 kg launched at 4.2 m). These characteristics, which are quite comparable with those of tubes made of composite materials or aluminum alloys, show that these sandwiches with birch core are serious candidates for energy absorption with renewable materials

Static and dynamic crushing of sandwich tubes with composite skins and three plywood cores (poplar, birch, and oak)

International audienceThis paper presents the results of static and dynamic crushing of sandwich tubes with carbon or glass skins and different wood cores. Wood cores were made with poplar, birch, or oak veneer. The core thicknesses of the tubes were equal even if the thicknesses of the species veneers were different for availability reasons. For a tube with a birch core and carbon skins, the Specific Energy Absorption was 50.4 J/g in quasi-static tests and 66.6 J/g in dynamic, and the energy absorbed was 5427 J in quasi-static and 7025 J in dynamic. The birch layers were shown to make a very significant contribution although they were 40 times less expensive than carbon layers. Results from the research work described here show that these materials are appropriate candidates for energy absorption at low carbon emission and with renewable materials

Wood as a structural material for transportation industry: Past example and recent advances

International audienceWood was the primary material in aviation until World War II [1]. We can mention the famous Mosquito nicknamed "the Wooden Wonder". Its structure is made up of sandwich panels with skins formed from birch plies and a balsa core. It was manufactured in 7781 samples, with a "one shot" half-fuselage production and could reach 612 km/h. Until the 1990s, the Mudry CAP10 acrobatic aircraft was made entirely of wood. There is also a recent version of this aircraft with a carbon wing spar known as the CAP10BK. Today, the Aura Aviation company [2] is once again offering a French wood carbon aerobatic aircraft. In the automotive sector, only the English Morgan offers cars with an ash superstructure but an aluminum chassis. At Le Mans 1967, the Costin-Nathan has a plywood wooden frame, the doors are in fiberglass and it weighs only 410 kg [3]. This brief and non-exhaustive historical reminder questions the intrinsic capacities of wood, especially if it is combined with current materials. This is why the members of the ICA started working on the subject in 2014. The studies focused on the manufacturing methodologies and the static response of plywood-based sandwiches with skins made of glass fibers, carbon fibers, flax fibers or aluminum [4]. These sandwiches were then subjected to impacts [5] and their compressive strength after impact was analyzed [6]. A first attempt of modeling was also carried out [7] and above all showed that the problem requires a lot of investigation. The very good compression characteristics observed convinced us to launch a second thesis still in progress on the crash. This area is particularly important because automobiles are sized according to the HIC (Head Injury Criteria), a criterion which establishes the maximum deceleration that a human being can withstand during a collision without having irreversible consequences. A first publication was recently accepted [8] which shows that poplar (one of the lightest temperate woods, very present in France and affordable) has an SEA (Specific Energy Absorption) of between 20 and 30 KJ / kg while the carbon is between 30 and 80 kJ / kg, while poplar veneers cost 40 times less. Tests with other species (oak, walnut, etc.) and with a carbon / poplar mix will also be presente

Dynamic crushing of wood-based sandwich composite tubes

International audienceThe paper presents the results of dynamic crushing of sandwich tubes that had skins made of carbon or glass fibres-with epoxy resin-and an I214 poplar ply core. By increasing the number of poplar plies from two to six, the absorbed energy is doubled, showing the significant contribution of the wood. The Specific Energy Absorption of sandwiches with carbon fibre skins oscillated between 49.4 and 60 J/g while that with glass fibre skins varied from 35.4 to 43.3 J/g

Caractérisation de tubes sandwichs bois-carbone pour des applications de crash

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Développement et caractérisation d'éco-structures composites à base de bois

International audienceLow carbon emission is a shared goal of all transportation industry. One way to match this expectation consists in the introduction of lightweight materials with high specific properties such as composites materials. Wood based materials combined with fibre-reinforcedpolymerappear to be good candidates if we introduce environmental aspects, safety considerations,and energy absorption capabilities. Thus, several sandwich configurations with plywood cores has been characterized to impact tests in order to quantify the energy absorption capability of such materials. A comparison of these results is proposed with the sandwich materials currently used in the aeronautics industry to be able to identify the potentiality of these new wood-based structures. We analyzed their post impact strength through compression after impact test. Finally, several structures were identified as good compromise solutions between residual strength and stiffness to replace actual sandwich structures. Regarding to their impact behaviour, and based on numerical models developed, manufacturing and testing of a crash box using wood based sandwich structures should be carried out in the future.Limiter les émissions de carbone est un objectif commun à toutes les industries du transport. Une façon de répondre à cette attente consiste à introduire des matériaux de plus en plus légers avec des propriétés spécifiques élevées tels que les matériaux composites. Les structures composites à base de bois semblent être de bons candidats si l’on considère à la fois les aspects environnementaux, les notions de sécurité,et les capacités d'absorption d'énergie. Ainsi, plusieurs configurations de sandwichs avec âme en contreplaqué ont été caractérisées à l’impact afin de quantifier leur capacité d’absorption d’énergie. Une comparaison de ces résultats est proposée avec les structures sandwichs utilisées actuellement dans l’industrie aéronautique de manière à pouvoir identifier le potentiel de ces nouvelles structures à base de bois. Nous avons analysé leurs propriétés résiduelles via un essai de compression après impact. Au final, plusieurs structures présentant un bon compromis entre résistance résiduelle et rigidité ont été identifiées pour remplacer les structures sandwichs actuelles. Sur la base de leur comportement à l'impact et des modèles numériques développés, la fabrication d’une crash box utilisant des matériaux sandwich à base de bois devrait être envisagée dans les années à venir

Développement et caractérisation d'éco-structures composites à base de bois

International audienceLow carbon emission is a shared goal of all transportation industry. One way to match this expectation consists in the introduction of lightweight materials with high specific properties such as composites materials. Wood based materials combined with fibre-reinforcedpolymerappear to be good candidates if we introduce environmental aspects, safety considerations,and energy absorption capabilities. Thus, several sandwich configurations with plywood cores has been characterized to impact tests in order to quantify the energy absorption capability of such materials. A comparison of these results is proposed with the sandwich materials currently used in the aeronautics industry to be able to identify the potentiality of these new wood-based structures. We analyzed their post impact strength through compression after impact test. Finally, several structures were identified as good compromise solutions between residual strength and stiffness to replace actual sandwich structures. Regarding to their impact behaviour, and based on numerical models developed, manufacturing and testing of a crash box using wood based sandwich structures should be carried out in the future.Limiter les émissions de carbone est un objectif commun à toutes les industries du transport. Une façon de répondre à cette attente consiste à introduire des matériaux de plus en plus légers avec des propriétés spécifiques élevées tels que les matériaux composites. Les structures composites à base de bois semblent être de bons candidats si l’on considère à la fois les aspects environnementaux, les notions de sécurité,et les capacités d'absorption d'énergie. Ainsi, plusieurs configurations de sandwichs avec âme en contreplaqué ont été caractérisées à l’impact afin de quantifier leur capacité d’absorption d’énergie. Une comparaison de ces résultats est proposée avec les structures sandwichs utilisées actuellement dans l’industrie aéronautique de manière à pouvoir identifier le potentiel de ces nouvelles structures à base de bois. Nous avons analysé leurs propriétés résiduelles via un essai de compression après impact. Au final, plusieurs structures présentant un bon compromis entre résistance résiduelle et rigidité ont été identifiées pour remplacer les structures sandwichs actuelles. Sur la base de leur comportement à l'impact et des modèles numériques développés, la fabrication d’une crash box utilisant des matériaux sandwich à base de bois devrait être envisagée dans les années à venir