scholarly journals Moisture-induced stresses and distortions in spruce cross-laminates and composite laminates

Holzforschung ◽  
2010 ◽  
Vol 64 (1) ◽  
Author(s):  
Thomas Gereke ◽  
Philipp Hass ◽  
Peter Niemz
Keyword(s):  
Composite Laminates ◽  
Oriented Strand Board ◽  
Medium Density Fiberboard ◽  
Middle Layer ◽  
Solid Wood ◽  
Shear Stresses ◽  
Wood Composite ◽  
Laminated Panels ◽  
Induced Stresses ◽  
Drying Test

Abstract The crosswise gluing of cross-laminated panels made of solid wood can cause problems when exposed to moisture variations. In the present study, the substitution of the spruce middle layer by a wood composite is tested for its influence on moisture-induced stresses and deformations in laboratory tests and numerical simulations. Furthermore, slits in the spruce middle layer were investigated. The hygroscopic warping due to a moisture gradient, stresses caused by moistening and cracks due to drying were studied. The results show larger warping in composite laminates compared to the spruce cross-laminate, which is governed by the modulus of elasticity of the middle layer. The in-plane swelling was found to be larger in composite laminates, while stresses were lower. The drying test discovered that cracks develop in the middle layer of spruce-medium density fiberboard laminates due to shear stresses and tensile stresses in the thickness direction. It was concluded that slits can be applied in the middle layer, as they have no significant influence on moisture-induced stresses but increase the thermal insulation. If the substitution of the spruce layer is required, the application of oriented strand board in the middle layer is recommended.

Comparison of results obtained by static 3- and 4-point bending and flexural vibration tests on solid wood, MDF, and 5-plywood

Holzforschung ◽  
2013 ◽  
Vol 67 (8) ◽  
pp. 941-948 ◽  
Author(s):  
Hiroshi Yoshihara
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Medium Density Fiberboard ◽  
Flexural Vibration ◽  
Solid Wood ◽  
Bending Tests ◽  
Four Point Bending ◽  
Flexural Vibration Test ◽  
The Difference ◽  
Vibration Tests

Abstract The flexural Young’s modulus of western hemlock, medium-density fiberboard, and 5-plywood (made of lauan) has been determined by conducting three- and four-point bending tests with various span lengths and by flexural vibration test. The Young’s modulus was significantly influenced by the deflection measurement method. In particular, the Young’s modulus was not reliable based on the difference between the deflections at two specific points in the specimen, although this test is standardized according to ISO 3349-1975 and JIS Z2101-2009.

Moisture Transport in Wood-Based Structural Panels under Transient Hygroscopic Conditions

2020 ◽  
Vol 70 (3) ◽  
pp. 283-292
Author(s):  
Daniel Way ◽  
Frederick A. Kamke ◽  
Arijit Sinha
Keyword(s):  
Moisture Transport ◽  
Transport Model ◽  
Oriented Strand Board ◽  
Primary Objective ◽  
Accelerated Weathering ◽  
Wood Composite ◽  
Transport Parameters ◽  
Moisture Profile ◽  
Cyclic Changes ◽  
Wood Based Composite

Abstract Development of moisture gradients within wood and wood-based composites can result in irreversible moisture-induced damage. Accelerated weathering (AW), generally employing harsh environmental conditions, is a common tool for assessing moisture durability of wood composite products. Use of milder AW conditions, such as cyclic changes in relative humidity (RH), may be of interest to the wood-based composites industry in assessing moisture durability under more realistic conditions. The primary objective of this study was to determine whether moisture profile development in oriented strand board and plywood during cyclic RH changes could be reasonably predicted with a simple moisture transport model, which may be practical for wood-based composite industry members seeking to develop new AW protocols. The diffusion model based on Fick's second law with empirically determined moisture transport parameters fits the experimental data reasonably well for the purpose of screening RH parameters.

scholarly journals Edge screw withdrawal resistance in conventional particleboard and OSB: Influence of the particles type

2007 ◽  
pp. 109-117
Author(s):  
Jovan Miljkovic ◽  
Mladjan Popovic ◽  
Milanka Djiporovic-Momcilovic ◽  
Ivana Gavrilovic-Grmusa
Keyword(s):  
Oriented Strand Board ◽  
Layer Structure ◽  
Middle Layer ◽  
Root Diameter ◽  
Mean Values ◽  
Pilot Hole ◽  
Wood Particles ◽  
Screw Withdrawal ◽  
Insight Into

This research was based on presumption that the changes in size and shape of wood particles are expected to have certain impact on the particleboard quality in general. Since the conventional particleboard (PB) and oriented strand board (OSB) were built of the quite diverse wood particles, they present interesting specimens in the comparison tests. In this work, the influence of the wood particles type on the edge screw holding performance of conventional particleboard and OSB was investigated. Those tests were obtained with the screw diameters of 4.0 mm, 4.5 mm and 5 mm. Depth of embedment was 30 mm for all tests and with the pilot-hole diameter kept in the range of 80-90% in respect of the screw root diameter. Additional tests of the thickness density profile and tensile strength perpendicular to the surface of the board were conducted. Since the middle layer structure of the particleboard embeds the screw body, both mentioned parameters are considered important in the aspect of the quality of the edge screw holding performance. In order to have further insight into the conformation of the middle layer the image survey was obtained on the split board section presenting the surface of the middle layer. Significant differences in the SWR performance of OSB and PB was recorded at all screw diameters. For the screw withdrawal tests parameters OSB samples showed 56-73% superior mean values then conventional PB. On the other hand, the OSB showed wider dispersions of measured withdrawal forces at all screw diameters, which might present some of the problems in certain engineering and project calculations.

scholarly journals Pre-Treatment of Furniture Waste for Smokeless Charcoal Production

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3188
Author(s):  
Paweł Kazimierski ◽  
Paulina Hercel ◽  
Katarzyna Januszewicz ◽  
Dariusz Kardaś
Keyword(s):  
Oriented Strand Board ◽  
Raw Materials ◽  
Medium Density Fiberboard ◽  
Fast Pyrolysis ◽  
Pyrolysis Product ◽  
Pyrolysis Process ◽  
Heating Rates ◽  
Charcoal Production ◽  
Pyrolysis Products ◽  
Slow Pyrolysis

The aim of this study was to assess the possibility of using furniture waste for smokeless fuel production using the pyrolysis process. Four types of wood-based wastes were used in the pyrolysis process: pine sawdust (PS), chipboard (CB), medium-density fiberboard (MDF), and oriented strand board (OSB). Additionally, the slow and fast types of pyrolysis were compared, where the heating rates were 15 °C/min and 100 °C/min, respectively. Chemical analyses of the raw materials and the pyrolysis product yields are presented. A significant calorific value rise was observed for the solid pyrolysis products (from approximately 17.5 MJ/kg for raw materials up to approximately 29 MJ/kg for slow pyrolysis products and 31 MJ/kg for fast pyrolysis products). A higher carbon content of char was observed in raw materials (from approximately 48% for raw materials up to approximately 75% for slow pyrolysis products and approximately 82% for fast pyrolysis products) than after the pyrolysis process. This work presents the possibility of utilizing waste furniture material that is mostly composed of wood, but is not commonly used as a substrate for conversion into low-emission fuel. The results prove that the proposed solution produced char characterized by the appropriate properties to be classified as smokeless coal.

Refined First-Order Shear Deformation Theory Models for Composite Laminates

2003 ◽  
Vol 70 (3) ◽  
pp. 381-390 ◽  
Author(s):  
F. Auricchio ◽  
E. Sacco
Keyword(s):  
Shear Deformation ◽  
Analytical Solutions ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Shear Deformation Theory ◽  
Quadratic Functions ◽  
Shear Stresses ◽  
Stress Profile ◽  
First Order ◽  
Out Of Plane

In the present work, new mixed variational formulations for a first-order shear deformation laminate theory are proposed. The out-of-plane stresses are considered as primary variables of the problem. In particular, the shear stress profile is represented either by independent piecewise quadratic functions in the thickness or by satisfying the three-dimensional equilibrium equations written in terms of midplane strains and curvatures. The developed formulations are characterized by several advantages: They do not require the use of shear correction factors as well as the out-of-plane shear stresses can be derived without post-processing procedures. Some numerical applications are presented in order to verify the effectiveness of the proposed formulations. In particular, analytical solutions obtained using the developed models are compared with the exact three-dimensional solution, with other classical laminate analytical solutions and with finite element results. Finally, we note that the proposed formulations may represent a rational base for the development of effective finite elements for composite laminates.

Cohesion and detachment in biofilm systems for different electron acceptor and donors

2007 ◽  
Vol 55 (8-9) ◽  
pp. 421-428 ◽  
Author(s):  
C. Coufort ◽  
N. Derlon ◽  
J. Ochoa-Chaves ◽  
A. Liné ◽  
E. Paul
Keyword(s):  
Basal Layer ◽  
Middle Layer ◽  
Electron Donors ◽  
Shear Stresses ◽  
Average Thickness ◽  
Low Shear Stress ◽  
Erosion Test ◽  
Biofilm Structure ◽  
Initial Biofilm ◽  
Low Shear

This work deals with the cohesion and detachment in biofilm systems for two electron acceptors and for two electron donors. Biofilms were developed on plates, under very low shear stress for one month and then subjected to an erosion test for two hours in a Couette-Taylor reactor. Biofilm was characterised in terms of average thickness and residual TOC mass. It was found that the biofilm structure is very heterogeneous and stratified. The top layer, which represents 60% of the biofilm mass, is very fragile and can be easily detached; the basal layer, which represents 20% of the biofilm mass, is very cohesive and can resist shear stresses up to 13 Pa. Between these two layers, a middle layer of intermediary cohesion represents 20% of the initial biofilm mass.

Water Absorption of Wood Composite Modified by Basalt Glass Powder

2013 ◽  
Vol 821-822 ◽  
pp. 1168-1170 ◽  
Author(s):  
Hua Wu Liu ◽  
Kai Fang Xie ◽  
Wei Wei Hu ◽  
Han Sun ◽  
Shu Wei Yang ◽  
...  
Keyword(s):  
Water Absorption ◽  
Glass Powder ◽  
Medium Density Fiberboard ◽  
Moisture Sorption ◽  
Wood Composite ◽  
Wood Composites ◽  
Thickness Swelling ◽  
Basalt Glass ◽  
Wood Sawdust ◽  
Dimensional Variation

Moisture sorption of wood sawdust panel results in dimensional variation, deterioration of mechanical property and fungi attack, which may be improved by the reinforcement of waterproof material. In this study, the fir sawdust panel was reinforced by basalt glass particles with size smaller than 5 micron, in order to reduce moisture penetration. When the content of basalt glass powder was 15%, both the thickness swelling and 24 h water absorption rate of wood composites reached their minimum values, which were 2.7% and 11%, respectively. The thickness swelling was far smaller than the 45% upper limit of medium density fiberboard as described by standards GB/T17657-1999.

Simultaneous measurement of elastic constants of full-size engineered wood-based panels by modal testing

Holzforschung ◽  
2016 ◽  
Vol 70 (7) ◽  
pp. 673-682 ◽  
Author(s):  
Jianhui Zhou ◽  
Ying Hei Chui ◽  
Meng Gong ◽  
Lin Hu
Keyword(s):  
Elastic Constants ◽  
Oriented Strand Board ◽  
Medium Density Fiberboard ◽  
Test Method ◽  
Modal Testing ◽  
Orthotropic Plates ◽  
Static Tests ◽  
Full Size ◽  
Structural Applications ◽  
Engineered Wood

Abstract Engineered wood-based panels are widely used in structural applications. Accurate measurement of their elastic properties is of great importance for predicting their mechanical behavior during structural design. In this study, an efficient non-destructive test method for measurement of effective elastic constants of orthotropic wood-based panels is proposed based on a modal testing technique. An algorithm was developed based on an improved approximate frequency equation of transverse vibration of orthotropic plates under the boundary condition, in which two opposite sides are simply supported and the other two are free (SFSF). The method is able to predict the frequency ranges and mode indices as well as corresponding normalized sensitivity to elastic constants based on initial estimates of orthotropic ratios with uncertainties and measured fundamental natural frequency. Full-size engineered wood-based panels including cross laminated timber (CLT), oriented strand board (OSB), and medium density fiberboard (MDF) were tested with the proposed method. In general, the measured elastic constants of the three types of panel based on modal test agreed well with those corresponding values measured by static tests. More tests are needed with a range of panel sizes and types for further validation of the proposed test method.

The variation in low speed impact strength on glass fiber/Kevlar composite hybrids

2020 ◽  
Vol 54 (21) ◽  
pp. 3009-3019 ◽  
Author(s):  
Jayna Kátia Dionísio dos Santos ◽  
Rayane Dantas da Cunha ◽  
Wanderley Ferreira de Amorim Junior ◽  
Renata Carla Tavares dos Santos Felipe ◽  
José Lira Braga Neto ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Glass Fiber ◽  
Residual Strength ◽  
Composite Laminates ◽  
Fiber Material ◽  
Middle Layer ◽  
Damage Area ◽  
Residual Properties ◽  
Layer Composite

The aim of this study was to analyze the effect of hybridization on impact and residual strength in composites as well as the types of damage caused by the impacts, quantifying the delaminated area of the test specimens. Two 11-layer composite laminates were developed, one with bidirectional glass fiber woven and the other a hybrid with three layers of bidirectional aramid fiber substituting the outer layers and the middle layer of the glass fiber. The materials revealed that the hybrid laminate obtained greater impact strength withstanding one impact of 76 J, albeit with an increase in the damaged area of between 64 and 85 cm2, resulting in a decline in mechanical properties along nearly the entire test specimen. This contrasts with what occurred in the glass fiber laminates, which recovered over 80% of their mechanical properties for a distance of 35 mm from the edge of the impactor. Moreover, it demonstrated that the variation in residual strength can be represented by an equation and that there is a relation between the damage area and the residual properties of the glass fiber material.

Sign in / Sign up

Export Citation Format

Share Document