Static Bending Properties Research Articles

Behavior of notched and unnotched [0/±30/±60/90]s GFR/EPOXY composites under static and fatigue loads

The main objective of the present paper is to study the bending behavior of notched and unnotched angle-ply, [0/±30/±60/90] s , glass fiber reinforced epoxy (GFRE) composites under static and fatigue loads. Static and fatigue bending properties have been determined for notched and unnotched angle-ply specimens. For this purpose different circular notch sizes (2, 4.5, 7, 9 mm) were drilled at the specimen center. Constant-deflection bending fatigue tests were performed at zero mean stress and 25 Hz. A 15% reduction of the initial applied moment was taken as a failure criterion. S–N diagrams for notched GFRE specimens have been constructed based on gross and net cross-section area. The results show that the ultimate bending strength of notched GFRE specimens decreased linearly with increasing notch diameter. Based on gross-section the fatigue life increases with decreasing notch size and the longer fatigue life was for the unnotched specimens. On the other hand, the S–N diagrams based on net-section indicate the insensitivity of angle-ply composites to the notch size. This is considered to be a peculiar phenomenon to composite materials. The results also show that the S–N diagrams have not any fatigue limit rigorous within 10 7 cycles.

PRODUCTION AND PROPERTIES OF A MEDIUM DENSITY WOOD-CEMENT BOARDS PRODUCED WITH ORIENTED STRANDS AND SILICA FUME

Wood-cement board (WCB) is a panel product that has the advantages of inorganic and organic materials. However, the main problems affecting the manufacture and use of WCB are the inhibitory effects of wood on the setting of cement and the high specific gravity of the final product. This paper examines the potential of strand orientation and the use of silica fume (SiO2) to facilitate the production of a medium density WCB from Pinus taeda. Oriented wood-cement boards (OWCB) were manufactured with wood/cement (w/w) ratio of 1:1, specific gravity 850 kg/m3; and SiO2 content as cement replacement of 0%, 10% and 20%. The OWCB were tested for static bending (MOR and MOE) properties in parallel (//) and perpendicular (^) directions; internal bond (IB); compression strength parallel to surface (CP); thickness swelling (TS) and water absorption (WA). The results showed that replacement of cement with 10% of SiO2, increased MOE (//), MOR (//) and CP and, decreased WA and TS, and most importantly eliminated the inhibitory effect of wood on cement setting. The principle of strand orientation was effective to produce boards with anisotropy in the flexural properties ranging form 2.1 to 2.8 for MOR and 2.6 to 3.8 for MOE. However, boards had very low IB strength and this shortcoming must be addressed in future research

Some of the properties of wood–plastic composites

In this study some of the important properties of experimentally manufactured wood–plastic composites (WPC) were determined. Specimen having 60% and 80% particle and fiber of radiata pine (Pinus radiata ) were mixed with polypropylene (plastic) and four different additives, namely Structor TR 016 which is coupling agent, CIBA anti-microbial agent (IRGAGUARD F3510) as fungicide, CIBA UV filter coating (TINUVIN 123S), CIBA blue pigment (Irgalite), and their combinations. Based on the initial finding of this work static bending properties of the samples enhanced as above chemicals were added into both particle and fiber-based specimens. Thickness swelling of the samples were also improved with having additives in the panels. Micrographs taken on scanning electron microscope (SEM) revealed that coupling agent and pigment resulted in more homogeneous mixture of wood and plastic together. Two surface roughness parameters average roughness (Ra) and maximum roughness (Rmax) used to evaluate surface characteristics of the samples showed that particle based samples had rougher surface characteristics than those of fiber based ones. No significant influence of chemicals added in the samples was found on surface roughness values of the samples manufactured from particle and fiber of radiata pine.

Mechanical and physical properties of agro-based fiberboard

In order to better utilize agricultural fibers as an alternative resource for composite panels, several variables were investigated to improve mechanical and physical properties of agro-based fiberboard. This study focused on the effect of fiber morphology, slenderness ratios (L/D), and fiber mixing combinations on panel properties. The panel construction types were also investigated such as hardboard (HB), medium density fiberboard (MDF), and bagasse core panel (BCP) made from bagasse/bamboo combinations with a combination of 1% pMDI/4% UF as a binder. Static bending properties and tensile strength increased as fiber L/D increased from 3 to 26. Fiber separation and morphology also influenced the mechanical property development of agro-based panels. Bagasse fiber bundles and particles smaller than L/D of 5.4 were responsible for the mechanical property loss of agro-based MDF. The BCP yielded promising results for modulus of elasticity (MOE) and modulus of rupture (MOR). However, HB appeared to be a better panel type for agro-based composites based on the property enhancement compared to wood-based panel products.

Enhancing environmental performance of formaldehyde‐based adhesive in lignocellulosic composites – Part II

Purpose – To investigate a new approach for the prevention of lignocellulosic composites based on agro‐fibres (e.g. sugar‐cane bagasse) from the emission of toxic formaldehyde.Design/methodology/approach – Five organic polymer containing nitrogen‐urea formaldehyde (UF) adhesive systems were used as bonding agents for bagasse fibres. The environmental performance of the lignocellulosic composites prepared were evaluated in terms of the effect of the organic polymers on the percentage of free formaldehyde in the adhesive system and the adhesion properties (static bending and water resistance properties) of the composite produced, in comparison with that prepared from un‐modified UF. The nitrogen content of the polymer and the amount of organic polymers incorporated in the adhesive system were optimised using the 3D response surface methodology and the multi‐linear regression technique.Findings – All investigated organic polymers (crude PAM‐g‐starch, PAM‐g‐starch, PAM, CE‐starch and Cm‐starch) were found to ...

Some of the properties of three-layer particleboard made from eastern redcedar

The objective of this study was to investigate the use of whole-tree eastern redcedar furnish ( Juniperus virginiana L.) in manufacturing three-layer particleboard panels. Static bending properties, internal bond strength, screw holding strength, and thickness swelling of the panels were determined according to the procedure of ASTM D-1037. Surface roughness and overlaying properties of the samples were also evaluated. No significant difference was found among the specimens prepared from 20 experimental panels at a 95% confidence level. Average physical and mechanical properties of the panels were found to be comparable to those of commercial particleboard manufactured from other species. Static bending and internal bond strength of the three-layer panels were, however, 18–20% lower than those of single-layer boards made from the same type of furnish in a previous study. Based on the findings of this study, it appears that three-layer particleboard can be manufactured from whole-tree furnish of low quality of eastern redcedar without having any adverse influence on properties of the panels.

1841 ポリ乳酸樹脂の機械的性質に及ぼす熱処理の影響(G03-6 生体材料・プラスチック,G03 材料力学)

Polylactide (PLA) is biodegradable and has relatively high strength in biodegradable plastics. Therefore, if PLA is reinforced, PLA has possibility to use as green plastics for industries. In this study, the purpose was to try to improve the mechanical property of PLA by crystallization with heat treatment. Mechanical properties were evaluated by static bending properties. At first, crystallinity adjustment method was established by isothermal crystallization. Consequently, as crystallinity was increased, the static bending properties were improved. However, static bending properties differed on the same crystallinity materials. Then, crystalline structure was observed using electron microscope, it was clarified that crystalline size varied according to heat treatment temperature. As a result, as heat treatment temperature increased, particle size of crystal was increased.

Static bending properties of Finnish birch wood

The purpose of this study was to determine the modulus of elasticity (MOE) and the modulus of rupture (MOR) in the radial bending test for small, clear specimens of Finnish birch (Betula pendula Roth and B. pubescens Ehrh) wood originating from mature trees. The dependency of MOE and MOR on the specific gravity of birch wood was studied, and the relationship between MOE and MOR was modelled at the different heights and at the different distances from the pith of the tree. For B. pendula, the mean values for MOE and MOR were 14.5 GPa and 114 MPa, whereas B. pubescens had means of 13.2 GPa and 104 MPa, respectively. At the corresponding specific gravity, the bending stiffness and strength values did not differ between the two species. The results indicated a linear relationship between the MOE and MOR, irrespective of the birch species or the within-stem location. Both MOE and MOR increased clearly from the pith towards the surface of the tree and decreased slightly from the base to the top of the tree. It seems that if products with as high stiffness and bending strength as possible are wanted, sorting of raw materials into different grades according to their within-tree origin can be of value.

Static and Dynamic Notched-bar Bending Properties of Ferritic Spheroidal Graphite Cast Iron

Static and Dynamic Notched-bar Bending Properties of Ferritic Spheroidal Graphite Cast Iron

US: Onaga — wood/plastic composites

In this study some of the important properties of experimentally manufactured wood–plastic composites (WPC) were determined. Specimen having 60% and 80% particle and fiber of radiata pine (Pinus radiata ) were mixed with polypropylene (plastic) and four different additives, namely Structor TR 016 which is coupling agent, CIBA anti-microbial agent (IRGAGUARD F3510) as fungicide, CIBA UV filter coating (TINUVIN 123S), CIBA blue pigment (Irgalite), and their combinations. Based on the initial finding of this work static bending properties of the samples enhanced as above chemicals were added into both particle and fiber-based specimens. Thickness swelling of the samples were also improved with having additives in the panels. Micrographs taken on scanning electron microscope (SEM) revealed that coupling agent and pigment resulted in more homogeneous mixture of wood and plastic together. Two surface roughness parameters average roughness (Ra) and maximum roughness (Rmax) used to evaluate surface characteristics of the samples showed that particle based samples had rougher surface characteristics than those of fiber based ones. No significant influence of chemicals added in the samples was found on surface roughness values of the samples manufactured from particle and fiber of radiata pine.

マトリックスハイブリッド積層板の力学的特性

Matrix hybrid laminates are defined to be materials fabricated by the combination of two or more kinds of matrices. The wide ranges of stiffness and damping property may be produced by changing various designing parameters, the resin ratio and/or the stacking sequence. In this study, two kinds of resins are used as matrices. One is a vinyl ester resin with high stiffness and the other is unsaturated polyester resin with low stiffness. As a reinforcement, plain woven glass cloth is used. Matrix hybrid laminates with various flexible resin ratios and stacking sequences are fabricated. The static and dynamic bending properties are investigated by the three-point bending and the vibration tests, respectively. In addition, antisymmetric matrix hybrid laminates are also investigated by the above tests. For the above all experimental results, the influences of designing parameters on both static and dynamic bending properties are discussed in detail. It is confirmed that matrix hybrid laminates can have the wide ranges of stiffness and damping properties by changing the flexible resin ratio and the stacking sequence.

Mechanical strength of tooth fragment reattachment.

The aim of this study was static and fatigue test investigation of the strength of a tooth fragment reattached with adhesives to the tooth body. Central bovine incisor teeth were used, and standardized fragments were obtained by cutting the incisal edge of the selected teeth. All the fragments were reattached using a multistep dentine adhesive system, and the specimens were randomly divided into two groups (A and B). Group B specimens underwent a further dental treatment: a circumferential double chamfer prepared around the external cut interface was filled with light cured composite restorative resin. Static and fatigue bending tests were performed and linear elastic equations were used to analyze and compare the strength of the treated teeth. The results indicated that the static and fatigue bending properties were improved by using reinforcement with composite restorative resin.

Effects of moisture content and specific gravity on static bending properties and hardness of six wood species

This study was designed to investigate the effects of moisture content (MC) and specific gravity (SG) on the bending strength and hardness of six wood species including Japanese cedar (Cryptomeria japonica D. Don), China fir (Cunninghamia lanceolata), western hemlock (Tsuga heterophylla), red meranti (Shorea spp.), Selangan batu (Shorea spp.), and red oak (Quercus spp.). The experimental results are summarized as follows: Effects of MC and SG on the strength (MOR), stiffness (MOE), and hardness (H B) could be represented by a multiregression formulas. A negative correlation existed between these properties and MC, whereas a postive correlation showed between them and the SG. The changing rate of these properties induced by 1% MC changes varied with the wood species: 2.6% change in MOR was observed in Japanese cedar, China fir, western hemlock, red meranti, and Selangan batu; and 3.9% was found in red oak. For MOE, a 0.58% change was observed in Japanese cedar, China fir, and red meranti; western hemlock and Selangan batu exhibited 1.2% and red oak 2.5%. For hardness, a 1.1% change was observed in Japanese cedar, western hemlock, and red oak; red meranti and China fir exhibited 3.3%; and Selangan batu 1.8%.

KNITTED CARBON FIBER REINFORCED THERMOPLASTICS

The paper provides an overview over a 4 years research work embedded in the framework of a BRITEEURAM Project. In this study, PEEK and PA12 as matrix systems intermingled with the carbon fiber yarns, either continuous or staple spun yarns, were investigated. Structure-properties relations of knitted fabric reinforced composites were elucidated varying systematically, fiber content, number of knit layers, yarn and matrix properties. The 3-dimensional fiber orientation in the composite was assessed by reconstruction of the bundle geometry from stacked cross sections. Static tensile and bending properties were determined at various angles between wale and course direction indicating a strong correlation between these properties and the respective knit orientation. Fatigue tests revealed a considerable influence of the yarn properties indicating a higher fatigue resistance for staple yarns than for continuous yarns. Fracture mechanical as well as impact failure studies supported the importance of the fiber bundle for the understanding of the properties of the composite and they proved the insensitivity of these materials against delamination and notch effects.

Selected Properties of Laboratory-Made Laminated-Bamboo Lumber

An exploratory study was conducted to evaluate the properties of laminated-bamboo lumber, herein referred to as LBL. Quasi-flattened Moso bamboo (Phyllostachys pubescens) were laminated using a resorcinol-based adhesive to form a composite which is similar in construction to that of laminated-veneer lumber (LVL). Representative samples were tested for static bending properties, internal bond strength, and dimensional stability. The effect of initial moisture content (10 and 15 percent) and glue spread rate (220, 320 and 420 g/m 2 single glueline) on LBL properties was also analyzed. Results indicate that LBL exhibits superior strength property compared to wood-based LVL, as indicated by its higher MOR. Its MOE, however, was slightly lower. Initial MC (within 15 percent) did not have a significant effect on the mechanical properties of LBL, but it appears to have a significant effect on dimensional stability. Glue spread rate had a significant effect on both the mechanical and physical properties.

Dry-Process Hardboards from Recycled Newsprint Paper Fibers

AbstractDry-process hardboard represents a favorable option for recycling old newspaper fibers. However, dry-process boards tend to be less dimensionally stable than boards processed by other methods. Our objective was to determine the effects of various wood fiber (WF) to old newspaper (ONP) ratios (100:0, 50:50, and 0:100 WF/ONP) on the mechanical strength and water resistance of dry-process hardboards made from these fibers. Untreated and acetylated hardboards were made with 3 or 7 percent resin and 0.5 percent wax. Boards were tested for static bending and tensile strength properties and water resistance. As expected, increasing the resin level from 3 to 7 percent generally improved all measured properties. Acetylation substantially improved the water resistance of all boards; increasing the amount of ONP caused a corresponding deterioration in both mechanical properties and water resistance.

Fatigue Properties of Junction of Crown and Bridge Resin and Metal Frame : (Part 2)Relationship between Surface Treatment or Adhesive and Static Bending Properties

Fatigue Properties of Junction of Crown and Bridge Resin and Metal Frame : (Part 2)Relationship between Surface Treatment or Adhesive and Static Bending Properties

The effect of chemical treatment of wood and polymer characteristics on the properties of wood–polymer composites

AbstractThe physical‐mechanical properties and the microscopic structure of caixeta (Chrysophyllum viride) and slash pine (Pinus elliottii) impregnated with polystyrene (PS) were investigated. The influences of a pretreatment with hydrogen peroxide (H2O2) solutions utilized in the production of the wood–polymer composites (WPC) and the characteristics of polystyrene formed in situ on the properties of WPC were analyzed. The incorporation of polystyrene improved the compression and static bending properties of slash pine and caixeta. The micrographies confirmed that there were distinct but continuous phases of polymer and wood cell wall which granted the composites a better physical‐mechanical behavior. The sensibilizing treatment with dilute hydrogen peroxide solution led to an increase in the viscosity average molecular weight (Mv) of polystyrene, and to the graft polymerization of the monomer, which, in turn, enhanced the stress properties of caixeta–polystyrene composites. Concentrated H2O2 solutions degraded caixeta wood, decreasing its tensile properties. Lower initiator concentration favoured higher molecular weight of polystyrene formed in pine wood. A fivefold increase in Mv of PS, however, had little effect on the compression properties of pine–polystyrene composites.