Preparation of High Strength Plywood from Partially Delignified Densified Wood

Wood and natural fibers exhibit an advantageous combination of good mechanics at comparably low density. Nevertheless, comparing absolute strength and stiffness, wood is clearly inferior to materials such as metals and engineered composites. Since there is a strong correlation between wood density and wood mechanical performance, densification by transversal compression suggests itself as a route towards improved mechanics. Partially delignified densified spruce veneers with excellent tensile properties were produced by means of an alkaline (AL) and an organosolv (OS) approach. Plywood specimens were manufactured using treated veneers glued with a phenol-resorcinol-formaldehyde adhesive and were compared with plywood samples made of native spruce veneers (Ref) and spruce veneer densified after plasticization by water impregnation (H2O). Roughly, the bending strength and the modulus of elasticity of plywood from partially delignified densified wood were improved by a factor of 2.4 and 3.5, respectively. Interlaminar shear strength did not match this improvement after partial delignification. Together with excessive thickness swelling, this might be a drawback of partially delignified densified wood in need for further research.

Download Full-text

FACTORS INFLUENCING REINFORCEMENT OF NR AND EPDM RUBBERS WITH SHORT ARAMID FIBERS

Rubber Chemistry and Technology ◽

10.5254/1.3570531 ◽

2011 ◽

Vol 84 (2) ◽

pp. 187-199 ◽

Cited By ~ 9

Author(s):

M. Shirazi ◽

J. W. M. Noordermeer

Keyword(s):

Low Cost ◽

High Strength ◽

Short Fiber ◽

Elastic Behavior ◽

Aramid Fibers ◽

Resorcinol Formaldehyde ◽

Fiber Coating ◽

Dog Bone ◽

Strength And Stiffness ◽

Microscopy Techniques

Abstract Among short fiber reinforced composites, those with rubbery matrices have gained great importance due to the advantages they have in processing and low cost, coupled with high strength. These composites combine the elastic behavior of rubbers with strength and stiffness of fibers. Aramid fibers have been chosen because of their significantly higher modulus and strength, compared to other commercial fibers. Compounds based on NR and EPDM are prepared. Short aramid fibers with different kinds of surface treatments, standard finish, and resorcinol formaldehyde latex (RFL)-coating result in different rubber–fiber interfaces. The reinforcing effect of these short aramid fibers is characterized by mechanical and viscoelastic experiments, and by studying the fracture surfaces with electron microscopy techniques. Related to the fiber coating and rubber curing system, sulfur- or peroxide-based, different reinforcement mechanisms are observed, where the combination of peroxide-cured EPDM with RFL-treated fibers is the only case showing clear signs of chemical adhesion. In all other combinations there are only indications of mechanical interactions of the fibers with the rubber matrices, due to bending/buckling of fibers, dog-bone shaped fiber ends, and surface roughness due to the RFL-coating.

Download Full-text

Intralaminar Reinforcement for Biomimetic Toughening of Bismaleimide Composites Using Nanostructured Materials

Materials ◽

10.1115/imece2005-81689 ◽

2005 ◽

Author(s):

Thomas Tiano ◽

Margaret Roylance ◽

Benjamin Harrison ◽

Richard Czerw

Keyword(s):

Shear Strength ◽

Carbon Fiber ◽

Laminated Composite ◽

High Strength ◽

Interlaminar Shear Strength ◽

Aircraft Wings ◽

Trailing Edges ◽

Interlaminar Shear ◽

Strength And Stiffness ◽

Walled Carbon Nanotubes

Many conventional composite materials are composed of multiple layers of continuous fiber reinforced resin produced by lamination of b-staged prepreg and subsequent cure. These materials exhibit very high strength and stiffness in the plane, dominated by the properties of the fibers. The Achilles heel of such composites is the interlaminar strength, which is dependent on the strength of the unreinforced resin, often leading to failure by delamination under load. Current methods for increasing the interlaminar shear strength of composites consist of inserting translaminar reinforcement fibers through the entire thickness of a laminated composite, such as z-pin technology developed by Foster-Miller [1]. While effective, this technique adds several processing steps, including ultrasonic insertion of the z-pins into the laminate, subsequently causing a significant cost increase to laminated composites. Described in this paper is a process utilizing single-walled carbon nanotubes (SWNTs) and vapor grown carbon nanofibers as reinforcing elements promoting interlaminar shear strength and toughness in carbon fiber/bismaleimide (BMI) resin composites. The resulting composites mimic the natural reinforcing mechanism utilized in insect cuticles. Three different methods of increasing the affinity of these carbon nanofillers for the BMI matrix were explored. The mechanical properties of these composites were assessed using end notch flexure testing. The results indicated that including nanofiller at the laminae interface could increase the interlaminar shear strength of carbon fiber/BMI composites by up to 58%. SEM micrographs revealed that the nanofiller successfully bridged the laminae of the composite, thus biomimicking the insect cuticle. Composite fabrication techniques developed on this program would have a wide variety of applications in space and aerospace structures including leading and trailing edges of aircraft wings.

Download Full-text

Mechanical Properties of Hydrogen Functionalized Graphyne - A Molecular Dynamics Investigation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.1813 ◽

2012 ◽

Vol 472-475 ◽

pp. 1813-1817 ◽

Cited By ~ 1

Author(s):

Yu Lin Yang ◽

Zhe Yong Fan ◽

Ning Wei ◽

Yong Ping Zheng

Keyword(s):

Mechanical Properties ◽

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Young’S Modulus ◽

Mechanical Performance ◽

Young's Modulus ◽

High Strength ◽

Strength And Stiffness ◽

Dynamics Simulations ◽

Structure Engineering

In this paper the mechanical properties of a series of hydrogen functionalized graphyne are investigated through acting tensile loads on the monolayer networks. Molecular dynamics simulations are performed to calculate the fracture strains and corresponding maximum forces for pristine graphyne along both armchair and zigzag directions. Furthermore, hydrogen functionalized graphynes with different functionalization sites are analyzed to investigate the effect of functionlization on the mechanical performance. Finally, Young's modulus of all the investigated architectures are computed. The obtained results show that monolayer graphyne is mechanically stable with high strength and stiffness, and the mechanical performance can be tuned through structure engineering and functionalization.

Download Full-text

Experimental Research on Physical and Mechanical Properties of Steel Fiber High-Strength Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.1061 ◽

2010 ◽

Vol 168-170 ◽

pp. 1061-1064 ◽

Cited By ~ 1

Author(s):

Yu Dong Wang ◽

Xiao Chun Fan

Keyword(s):

High Strength Concrete ◽

Bending Strength ◽

Steel Fiber ◽

Mechanical Performance ◽

Physical And Mechanical Properties ◽

Drying Shrinkage ◽

High Strength ◽

Engineering Practice ◽

Strength Concrete ◽

Mix Proportion

Based on experiment, the mix proportion matching with the design and construction requirements is obtained. It meets with the requirement of pump structure on the basis of meeting the strength requirement. On this basis, the basic physical and mechanical performance is studied and the conclusion is that steel fiber high-strength concrete has excellent resistance to splitting, bending and drying shrinkage. The splitting strength and bending strength of steel fiber high-strength concrete named CF60-2 is respectively 38.7% and 56.8% higher than that of plane concrete named C60. The drying shrinkage rate of CF60-2 is 45.5% lower than that of C60 in three days. The results have an important guiding significance to steel fiber high-strength concrete in theoretical and engineering practice.

Download Full-text

Investigation of the mechanical and thermal characteristics of an eco-insulating material made of plaster and date palm fibers

Selected Scientific Papers - Journal of Civil Engineering ◽

10.2478/sspjce-2021-0016 ◽

2021 ◽

Vol 16 (2) ◽

pp. 55-66

Author(s):

Mokhtar Rachedi ◽

Abdelouahed Kriker

Keyword(s):

Building Materials ◽

Date Palm ◽

Bending Strength ◽

Mechanical Performance ◽

Negative Impact ◽

Low Cost ◽

Natural Fibers ◽

Thermal Characteristics ◽

Chemical Degradation ◽

Date Palm Fibers

Abstract The negative impact of the production and use of building materials on the environment has become evident, so in recent decades, to find more sustainable, eco-friendly, and low-cost materials, the last research tends to reconsider the use of natural fibers and traditional building materials. This paper aims to develop a bio-composite based on the southern Algerian region's local materials consisting mainly of plaster and waste from date palm trees. Many properties were examined experimentally through previous research of our team (physical, mechanical, and microstructure characteristics) [1, 2] to characterize these materials. Several samples of bio-composite of plaster configurations with short length (20mm) and eight-weight ratios (0.5% - 4%) of palm fibers were prepared for mechanical, thermal, and physical characterizations. In addition, tested all previous properties on the specimens after 28 days of curing in normal conditions. The results show a clear improvement in the bio-composites mechanical performance (an increase in the bending strength with achieving compressive strength) and their thermal properties, which have been well developed (density, thermal conductivity, and specific heat capacity). To enhance the resistance of palm fibers to chemical degradation in the plaster's alkaline environment and improve the adhesion between them, these fibers were treated with a NaOH solution of 1% concentration. The plaster's composites reinforced with date palm fibers can be qualified as eco-friendly and thermal insulation building materials.

Download Full-text

Mechanical and Geometric Performance of PLA-Based Polymer Composites Processed by the Fused Filament Fabrication Additive Manufacturing Technique

Materials ◽

10.3390/ma13081924 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1924 ◽

Cited By ~ 3

Author(s):

José María Reverte ◽

Miguel Ángel Caminero ◽

Jesús Miguel Chacón ◽

Eustaquio García-Plaza ◽

Pedro José Núñez ◽

...

Keyword(s):

Carbon Fibre ◽

Mechanical Performance ◽

Dimensional Accuracy ◽

Point Of View ◽

Fused Filament Fabrication ◽

Sem Images ◽

Tensile Performance ◽

Interlaminar Shear ◽

Strength And Stiffness ◽

Short Carbon

In this work, the effect of short carbon fibre (CF) on the mechanical and geometric properties of 3D printed polylactic acid (PLA) composite parts processed using the Fused Filament Fabrication (FFF) technique have been analysed. Tensile, flexural and interlaminar shear strength (ILSS) tests were performed to obtain the mechanical performance of the different samples. The surface quality and geometric accuracy of the printed specimens were also evaluated. Finally, Scanning Electron Microscope (SEM) images of the printed samples are analysed. The results revealed that the addition of carbon fibres effectively improved all assessed mechanical properties of PLA-CF composites as compared to the neat PLA. In particular, Flat PLA-CF samples showed an average increase in tensile performance of 47.1% for the tensile strength and 179.9% for the tensile stiffness in comparison to the neat PLA. From the flexural behaviour point of view, Flat PLA-CF samples revealed an increase in average flexural strength and stiffness of 89.75% and 230.95%, respectively in comparison to the neat PLA. Furthermore, PLA-CF samples depicted the best ILSS performance. In general, the use of short carbon fibre as reinforcement did not affect the dimensional accuracy of the PLA-CF samples, and even improved the surface roughness in certain cases, particularly in Flat and On-edge orientations.

Download Full-text

Effects of core grain orientation on the mechanical properties of wood sandwich composite

Journal of Tropical Resources and Sustainable Science (JTRSS) ◽

10.47253/jtrss.v6i1.723 ◽

2021 ◽

Vol 6 (1) ◽

pp. 27-30

Author(s):

Noor Sharina Azrin Zakari ◽

Julie Juliewatty Mohamed ◽

Nurul Basyirah Aryani Abdul Rahman ◽

Slina Anjang Ab Rahman ◽

Zairul Amin Rabidin

Keyword(s):

Grain Orientation ◽

Mechanical Performance ◽

High Strength ◽

Sandwich Composite ◽

Supporting Cells ◽

Parallel Direction ◽

Plane Direction ◽

Continuous Support ◽

Strength And Stiffness ◽

Core Materials

Utilization of sandwich composite during recent year has been driven by the fact that compositematerial has ultimately high strength and stiffness by weight than any other materials. The skins ofsandwich composites technically bear most of the applied loads, however, the core materials alsoplay an important role as it functions in providing continuous support to resist the shear stress.Hence, proper selection of core materials is required to establish a sturdy sandwich compositestructure. This paper presents an experimental investigation on the sandwich structure consists offibreglass/epoxy face skins and a mahang wood core. Sandwich composite with core grain orientedin parallel and perpendicular to the flat plane direction were tested for mechanical performance intension, compression and flexure. The results indicate that sandwich composite with grain orientedin parallel direction performed better in tensile properties with strength of 201.98 MPa whereassandwich composite with perpendicular core grain produced a higher value of compressionproperties with strength of 70.11 MPa. However, no significant effect of grain orientation wasobserved in flexural strength. The strength of sandwich composite is dependent on the grainalignment of the wood core as it functions exclusively as mechanical supporting cells to supportthe wood structure.

Download Full-text

Mixed Visual and Machine Grading to Select Eucalyptus grandis Poles into High-Strength Classes

Forests ◽

10.3390/f12121804 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1804

Author(s):

Michele Brunetti ◽

Giovanni Aminti ◽

C. Brand Wessels ◽

Michela Nocetti

Keyword(s):

Modulus Of Elasticity ◽

Dynamic Modulus ◽

Bending Strength ◽

Eucalyptus Grandis ◽

High Strength ◽

Multivariate Regression Analysis ◽

Acoustic Velocity ◽

Dynamic Modulus Of Elasticity ◽

Graded Material ◽

Strength And Stiffness

Before round timber can be profitably used in construction, it needs structural characterization. The visual grading of Eucalyptus grandis poles was integrated with additional parameters developed by multivariate regression analysis. Acoustic velocity and dynamic modulus of elasticity were combined with density and pole diameter in the estimation of bending strength and stiffness. The best models achieved were used to group the visually graded material into qualitative structural classes. Overall, dynamic modulus of elasticity was the best single predictor; and adding density and diameter to the model improved the estimation of strength but not of stiffness. The developed parameters separated the material into two classes with very distinct mechanical properties. The models including velocity as a parameter did not perform as well. The strength grading of Eucalyptus grandis poles can be effectively improved by combining visual parameters and nondestructive measurements. The determination of the dynamic modulus of elasticity as a grading parameter should be preferred over that of acoustic velocity.

Download Full-text

Electrophoresis deposited halloysite nanotubes as modifying additive for carbon fiber and CFRP

Modern Physics Letters B ◽

10.1142/s0217984919400232 ◽

2019 ◽

Vol 33 (14n15) ◽

pp. 1940023 ◽

Cited By ~ 2

Author(s):

Tianyu Yu ◽

Zixuan Chen ◽

Soo-Jeong Park ◽

Yun-Hae Kim

Keyword(s):

Carbon Fiber ◽

Bending Strength ◽

Sodium Dodecyl ◽

High Strength ◽

Halloysite Nanotubes ◽

Fiber Reinforced Polymers ◽

Carbon Fiber Reinforced Polymers ◽

Mode Ii Fracture Toughness ◽

Interlaminar Shear ◽

Fabric Surface

Carbon-fiber reinforced polymers (CFRPs) are widely applied to high-grade, precision and advanced industry fields due to its high strength-to-weight and stiffness-to-weight ratios. However, its poor through-thickness properties is becoming an issue. The objective of this study is to examine electrophoresis deposition (EPD) process of depositing halloysite nanotubes (HNTs) onto the carbon fabric surface for enhancing the through-thickness strength. The neutral HNTs were negatively charged and dispersed by adding sodium dodecyl sulfate (SDS) in aqueous solution and the CFRPs were fabricated using Vacuum-assisted Resin Transfer Molding (VaRTM). The bending strength and modulus, interlaminar shear strength, Mode I and Mode II fracture toughness were obtained according to ASTM standards. Electronic scanning microscope (SEM) were adopted to do the micromorphology observation.

Download Full-text