Influence of Specimen Size on Accelerated Weathering of Laminated Veneer Lumber

2019 ◽  
Vol 69 (1) ◽  
pp. 70-80
Author(s):  
Daniel Way ◽  
Frederick A. Kamke ◽  
Arijit Sinha
Keyword(s):  
Mechanical Properties ◽  
Edge Effect ◽  
Edge Effects ◽  
Total Surface Area ◽  
Specimen Size ◽  
Accelerated Weathering ◽  
Surface Area Ratio ◽  
Constant Length ◽  
Laminated Veneer Lumber ◽  
Durability Assessment

Abstract Moisture intrusion can be significantly higher along specimen edges, particularly at edges where longitudinal grain is exposed, which is referred to as the edge effect. The influence of edge effects on moisture durability are assumed to decrease as the edge area to total-surface-area ratio decreases. Moisture durability assessment of laminated veneer lumber (LVL) is commonly evaluated using accelerated weathering (AW) and outdoor exposure methods, where small specimens are analyzed. The influence of specimen size (i.e., edge effect) on moisture durability evaluation of LVL was investigated in this study. To vary specimen size, three widths with constant length and thickness were evaluated. In addition, three AW methods were used to characterize how the method of inflicting degradation influenced edge effects. No consistent trends in mechanical property loss were found across AW methods, indicating that the influence of specimen size varied with AW method. The greatest influence of specimen size occurred when cyclic vacuum-soak-dry was included, where water absorption decreased significantly with increasing width, and three of four mechanical properties evaluated displayed an influence of specimen size. The smallest influence of specimen size occurred when a single soak-dry procedure was included, where only one of four mechanical properties evaluated displayed an influence of specimen size. Results from this study provide evidence that edge effects may occur during LVL moisture durability assessment but that the severity is dependent on AW conditions.

scholarly journals Tentative Investigations on Reducing the Edge Effects in Pre-Polishing the Optics

2020 ◽  
Vol 10 (15) ◽  
pp. 5286
Author(s):  
Xiaolong Ke ◽  
Lei Qiu ◽  
Chunjin Wang ◽  
Zhenzhong Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Edge Effect ◽  
Edge Effects ◽  
Material Removal ◽  
Processing Time ◽  
Grinding Process ◽  
Element Analysis ◽  
Edge Zone ◽  
The Finite Element Analysis

The material removal depth in the pre-polishing stage of the precision optics is usually tens of microns to remove the subsurface damage and grinding marks left by the previous grinding process. This processing of the upstand edge takes a large part of the time at this stage. The purpose of this paper is to develop a method that can reduce the edge effect and largely shorten the processing time of the pre-polishing stage adopting the semirigid (SR) bonnet. The generation of the edge effect is presented based on the finite element analysis of the contact pressure at the edge zone firstly. Then, some experimentations on the edge effect are conducted, and the results proved that the SR bonnet tool can overhang the workpiece edge in the pre-polishing stage to reduce the width and height of the upstand edge to largely shorten the subsequent processing time of it. In addition, there exists a perfect overhang ratio, which generates the upstand edge with the smallest width and height, with no damage to the bonnet tool in the meantime. In addition, one combination of the pre-polishing parameters is concluded according to this method, which can be safely adopted in practical process.

Size Effect on Mechanical Properties of LVL

2014 ◽  
Vol 887-888 ◽  
pp. 824-829
Author(s):  
Qing Fang Lv ◽  
Ji Hong Qin ◽  
Ran Zhu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Size Effect ◽  
Tensile Test ◽  
Compression Test ◽  
Test Results ◽  
Laminated Veneer Lumber ◽  
Object Of Study ◽  
The Relationship

Laminated veneer lumber is taken as an object of study, and use LVL specimens of different sizes for compression test and tensile test. The goal of the experiment is to investigate the size effect on compressive strength and tensile strength as well as the influence of the secondary glued laminated face, which appears in the secondary molding processes. The results show that both compressive strength and tensile strength have the size effect apparently and the existence of the secondary glued laminated face lower the compressive strength of LVL specimens. Afterwards, the relationship between compressive strength and volume along with tensile strength and area are obtained by the test results.

scholarly journals Comparison of Bonding Performance Between Plywood and Laminated Veneer Lumber Induced by High Voltage Electrostatic Field.

2019 ◽  
Vol 275 ◽  
pp. 01013
Author(s):  
Qian He ◽  
Tianyi Zhan ◽  
Haiyang Zhang ◽  
Zehui Ju ◽  
Lu Hong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Voltage ◽  
Electrostatic Field ◽  
Wood Surface ◽  
Bonding Strength ◽  
Surface Characteristics ◽  
Wood Failure ◽  
Photoelectron Spectra ◽  
Masson Pine ◽  
Laminated Veneer Lumber

High voltage electrostatic field (HVEF) was applied in order to improve wood surface characteristics, bonding and mechanical properties of wood composites. Masson pine (Pinus massoniana Lamp.) plywood and laminated veneer lumber (LVL) were selected in this study. Surface characteristics were conducted by the electron spin resonance (ESR) and X-ray photoelectron spectra (XPS). Bonding interphase and mechanical properties were investigated by fluorescence microscopy and vertical density profile (VDP), bonding strength, wood failure ratio, MOE and MOR. The results indicated that more increments were obtained in free radicals, O/C ratios and C2-C4 components. This is because electrons broke more wood chemical groups and new ions occurred among wood surface under HVEF. Significantly decreased PF adhesive penetration depth (PD) and increased density at bonding interphase was achieved in HVEF treated composites. More decrease of PD and increment of density were observed in plywood than that of LVL. This was attributed to cross linked wood fibers among bonding interphase in plywood. Mechanical properties of bonding strength, wood failure ratio, MOE and MOR were significantly increased under HVEF treatment both for two composites. Higher bonding strength, MOE and MOR were obtained in plywood and their increments were as 98.53%, 33.33%, 18.55% and 12.72%.

The Dominant Factor Analysis of Dynamic Shear Modulus of Poplar LVL Based on Grey Theory

2010 ◽  
Vol 113-116 ◽  
pp. 811-814
Author(s):  
Feng Li ◽  
Ying Cheng Hu
Keyword(s):  
Mechanical Properties ◽  
Production Technology ◽  
Dominant Factor ◽  
Process Conditions ◽  
Dynamic Shear Modulus ◽  
Grey Theory ◽  
Dynamic Shear ◽  
Experimental Conditions ◽  
Laminated Veneer Lumber ◽  
Press Temperature

Wood is one kind of natural renewable eco-material. Laminated veneer lumber (LVL) is an engineered wood product made from veneers glued together with parallelly oriented grains under heat and pressure. This paper designed Poplar LVL production experiments under different process conditions, and measured the mechanical properties of poplar LVL specimens under different experimental conditions. In this study, grey theory was used to analyze the influences of different production processes on the mechanical properties, such as press duration, press temperature, pressure and adhesive spread. The results showed that, it is feasible that grey theory is used to analyze the influence level of production technology of poplar LVL on the mechanical properties. So this paper offered a new method to analyze and design the production technology of LVL.

scholarly journals Mechanical properties and fracture dynamics of silicene membranes

2014 ◽  
Vol 16 (36) ◽  
pp. 19417-19423 ◽  
Author(s):  
T. Botari ◽  
E. Perim ◽  
P. A. S. Autreto ◽  
A. C. T. van Duin ◽  
R. Paupitz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Temperature Dependence ◽  
Young’S Modulus ◽  
Edge Effects ◽  
Critical Strain ◽  
Young's Modulus ◽  
Stress Distributions ◽  
Fracture Dynamics ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

A thorough study on the mechanical properties of silicene membranes. Young's modulus, Poisson's ratios, critical strain values, edge effects, dynamics of edge reconstructions, temperature dependence and stress distributions were investigated.

Fatigue responses of cracked Ti/APC-2 nanocomposite laminates at elevated temperature

2019 ◽  
Vol 54 (13) ◽  
pp. 1705-1715
Author(s):  
MHR Jen ◽  
GT Kuo ◽  
YH Wu ◽  
YJ Chen
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Composite Laminates ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Cyclic Tests ◽  
Constant Length ◽  
Nano Powder ◽  
Strength And Stiffness ◽  
Inclined Angle

The mechanical properties and fatigue responses of Ti/APC-2 neat and nanocomposites with inclined single-edged cracks due to tensile and cyclic tests at elevated temperature were investigated. Two types of composite laminates [Ti/(0/90)s/Ti] were fabricated with and without (W/WO) nanoparticles SiO2 of optimal 1 wt.%. The geometry and dimensions of specimens were L × W × t = 240 × 25 × 1.55 mm3. The cracks were of constant length 3 mm and width 0.3 mm. The inclined angles were 0°, 45°, and 60°. Both the tensile and cyclic tests were conducted at elevated temperatures 25℃ (RT), 100℃, 125℃, and 150℃. From the tensile tests we obtained the load vs. displacement curves for both types of laminates with varied inclinations at elevated temperatures. Next, we received the applied load vs. cycles curves for the same laminates with inclined cracks at the corresponding temperature due to cyclic tests. According to the experimental data of both tensile and cyclic tests the mechanical properties, such as strength, stiffness, and life, decreased as the temperature rises. The greater the inclined angles were, the greater the strength and stiffness were. Similarly, the fatigue life was in the same trend. However, the effect of inclined angle on mechanical properties was more strong than those of temperature. The mechanical properties of nanocomposite laminates were higher than those of neat composite laminates, but not significant. The main reason was that the enhancement of spreading nano-powder silica on the laminate interfaces did not effectively eliminate the stress intensity at the crack tip locally.

scholarly journals Vegetable Tannin as a Sustainable UV Stabilizer for Polyurethane Foams

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 480 ◽  
Author(s):  
Maria Oliviero ◽  
Mariamelia Stanzione ◽  
Marco D’Auria ◽  
Luigi Sorrentino ◽  
Salvatore Iannace ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Uv Radiation ◽  
Polyurethane Foams ◽  
Accelerated Weathering ◽  
Polyphenolic Compound ◽  
Uv Treatment ◽  
Blowing Agent ◽  
Performance Change ◽  
Urethane Linkage ◽  
Vegetable Tannin

A vegetable tannin, a flavonoid-type natural polyphenolic compound, was used to promote the stabilization of polyurethane foams against UV radiation. Several polyurethane foams were synthesized by using an isocyanate, and a mixture of ethoxylated cocoalkyl amine and vegetable tannin. The content of vegetable tannin was varied from 0 to 40 wt %. The effects of tannin and water (used as a blowing agent) on the foaming kinetics and cellular morphology of foams were investigated. Samples were subjected to accelerated weathering under UV radiation for 3 to 24 h, and FTIR and DMA analyses were conducted to assess the performance change. The former analysis revealed a strong inhibiting effect of tannin on urethane linkage degradation during the UV treatment. The mechanical properties were significantly affected by the addition of tannin. The capability of the foams to withstand UV radiation was dependent on the amount of tannin. At tannin contents higher than 20%, the decrease in mechanical properties under UV irradiation was almost avoided.

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