Abstract Balsa wood is an appropriate core material for structural sandwich applications due to its high strength- and stiffness-to-weight ratios. However, the mechanical properties vary considerably owing to the inherent scattering of natural wood materials. One approach to reduce this scatter and tailor the mechanical properties according to specific application needs is to recompose the natural material into a veneered material consisting of veneer layers of different grain orientations, which are adhesively bonded together. The mechanical properties of such a veneered balsa wood, composed of alternating 0°/90° grain orientations, were investigated at ambient temperature according to corresponding standards. The properties were significantly influenced by the orthotropy on the material scale within one veneer layer and on the system scale within the assembled veneer layers. Standardized experimental set-ups and specimen geometries may produce artifacts such as buckling or strain hardening which deviate from the material behavior in real structures. The thin adhesive between the veneer layers did not negatively affect the mechanical behavior since failure occurred within the veneer layers and not in the interfaces.
#1M. Mohammadi(OSU: Oregon State University)H-Index: 9
#2John A. Nairn(OSU: Oregon State University)H-Index: 49
Abstract We examined various fracture properties relevant to the use of balsa as a thick core material in sandwich composites with unidirectional glass fiber/vinyl ester composite skins designed for bridge decks. The first experiments compared the fracture toughness of a laminated veneer lumber (LVL) made from balsa to the toughness of conventional butcher-block balsa material. When using a good lamination adhesive, an LVL balsa core material has enhanced toughness compared to solid balsa and th...
In this study, an experimental campaign was conducted to characterize the length effect on the elasticity and tensile strength of clear spruce wood parallel to the grain direction. Four groups of specimens of different lengths, cut from the same log, were tested under the same conditions under longitudinal tensile loading. The cross-sectional area of the specimens was selected as being constant and sufficiently small to exclude the effect of variations of the properties in the transverse directi...
The mechanical properties of plantation-grown balsa wood from Papua New Guinea (PNG) were determined according to American Society for Testing and Materials D143-09. Static bending, hardness, compression parallel and perpendicular to grain, and shear parallel to grain tests were performed on kiln-dried specimens segregated into the three international density classes (80 ≤ 120, 120 ≤ 180 and 180 ≤ 220 kg/m3). The literature states balsa with a density between 120 and 180 kg/m3 has the most comme...
Substantial quantities of senile coconut palms are present in plantations within the Asia-Pacific region. Once coconut palms become over-mature, their production of traditional products, such as coconuts, significantly decreases, resulting in profitability challenges for farmers. Presently, few profitable markets exist for over-mature, senile coconut palms. Using the coconut palm stem in composite or engineered wood products could, however, provide an attractive alternative. Due to some of its u...
#1Michael Osei-Antwi(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 6
#2Julia de Castro(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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The span limits of two glass fiber-reinforced polymer (GFRP) bridge concepts involving GFRP-balsa sandwich plates are discussed. The sandwich plates were either used directly as slab bridges or as decks of a hybrid sandwich-steel girder bridges. In the latter case, the potential of the sandwich decks to replace reinforced concrete (RC) decks was also evaluated. Taking the limits of manufacturing into account (800 mm slab thickness), maximum bridge spans of approximately 19 m can be reached with ...
Last. Michael Osei-Antwi(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 6
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The concept, design and experimental validation of the new Avancon Bridge in Bex, Switzerland, are described. The lightweight glass fiber-reinforced polymer (GFRP) sandwich bridge deck adhesively bonded to steel girders reduced the traffic disruption period by approximately 40 days or 80% compared to a cast-in-place concrete bridge and also enabled the bridge to be widened to two lanes. The semi-integral bridge concept allows the application of a continuous asphalt layer across the abutments wit...
#1Michael Osei-Antwi(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 6
#2Julia de Castro(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 15
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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An experimental study was performed using Iosipescu specimens to evaluate the effects of parameters such as shear plane, density and adhesive joints on the shear stiffness and strength of balsa wood panels as well as the variation of ductility with respect to the shear planes. The shear planes exerted a significant effect on shear stiffness and strength. Highest values were Obtained for the shear plane parallel to the end grain, intermediate values for the plane parallel to the flat grain and lo...
#2Swapan Kumar Sarker(SUST: Shahjalal University of Science and Technology)H-Index: 11
Last. Sanjay Saha Sonet(SUST: Shahjalal University of Science and Technology)H-Index: 4
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Timber species grouping (TSG) is essential for meaningful and cost-optimal use of wood. Bangladesh forests are exceedingly diverse and comprise many woody species which are potentially suitable for versatile uses including structural materials. Traditionally, widely known tree species are used for structural timber because technological properties of most of the species are poorly known. In this study, a hierarchical agglomerative cluster analysis based on three selected wood properties [i.e., w...
#1Young W. Kwon(NPS: Naval Postgraduate School)H-Index: 26
#2M. A. Violette(NPS: Naval Postgraduate School)H-Index: 1
Last. J. M. Didoszak(NPS: Naval Postgraduate School)H-Index: 1
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The objective of this study is to examine the Fluid Structure Interaction (FSI) effect on transient dynamic response and failure of sandwich composite structures under impact loading. The primary sandwich composite used in this study consisted of a 6.35 mm balsa core and a multi-ply symmetrical plain weave 6 oz E-glass skin. Both clamped sandwich composite plates and beams were studied using a uniquely designed vertical drop-weight testing machine. There were three impact conditions on which the...
Abstract This paper presents an experimental investigation on impact response of sandwich composite panels with PVC foam core and balsa wood core. A number of tests were performed under various impact energies. Damage process of the sandwich composites is analyzed from cross-examining load–deflection curves, energy profile diagrams and the damaged specimens. The primary damage modes observed are; fiber fractures at upper and lower skins, delaminations between adjacent glass–epoxy layers, core sh...
Last. Chiara Bertolin(NTNU: Norwegian University of Science and Technology)H-Index: 15
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Abstract An attempt was made to investigate the Michalski’s proven fluctuation theory through the use of the fracture characteristic and the energy density – dynamic surface value – of Scots pine coated with Renaissance wax, paraloid, and tar. The slices were acclimatized in a climate chamber with an abrupt drop of relative humidity from 80% to 30% while being monitored by acoustic emission. During this period, macro-cracks were formed in the slices coated with the paraloid and tar while those c...