Bending Strength Parallel Research Articles

Investigation of Flexural Strength of African Copalwood (Daniella Oliveri) as Reinforcement in Concrete Slab

This study investigates the potential of African Copalwood as a reinforcing material in concrete slabs. The timber rods were randomly selected from the timber market because there is always variation in timber properties with position in stem, location and soil condition. Various test specimen were prepared according to the Code of practices BS EN 408:2003 using structural size specimens. Thirty (30) slabs of size 75 mm x 300 mm x 700 mm were cast in five sets (1 to 4%) for Timber-reinforced concrete slab (TRCS) and Steel-reinforced slab (SRS) with a mix ratio of 0.5:1:2:4 denoting water-cement ratio, cement, fine and coarse aggregate respectively. Longitudinal bars were varied in 1% to 4% slab cross-sectional area in different TRCS samples while the transverse bar was restricted to be 3% by standard and made constant in all the slab samples specimen. A 10 mm diameter steel bar is used as reinforcement in the SRS. Findings revealed that the mean failure stress for Tensile strength parallel to grain was 41.80 N/mm2, Bending strength parallel to grain was 37.05 N/mm2, Compression parallel to grain was 13.48 N/mm2, Compression perpendicular to grain was 8.88 N/mm2, Local Modulus of Elasticity (MOE) was 3800.17 N/mm2, Apparent MOE was 59.42 N/mm2. Also, with regards to TRCS, the flexural strength test at 28 days for 1% to 4% reinforcement in concrete slabs is 3.61, 5.29, 5.49 and 7.22 N/mm2 respectively. The SRS has a flexural strength of 11.54 N/mm2 at 87.5% composition in slabs. These findings indicate enhancement in the strength properties of the concrete slabs with the incorporation of the African Copalwood reinforcement.

Compression properties of glued laminated timber and tensile properties of gluelam lamellas from oil palm wood

ABSTRACT When oil palm lumber is considered for load-bearing products such as glued laminated timber (GLT), defined strength and stiffness values are required. In this investigation, combined GLT from oil palm wood is tested in compression parallel and perpendicular and glulam lamellas in tension parallel to the vascular bundles. Strength and Young´s modulus in compression and tension parallel increase with the density by power law relationship. In contrast to dicotyle­dons, the strength in construction size exceeds that of small, defect-free test specimens (compression strength perpendicular), are in the same range (tensile and bending strength parallel) or only a little below (compression strength parallel). The specimen size does not influence the strength. The ratio of fc,0 : fm : ft,0 is 1.2 : 0.8 … 1.7 … 2.6 : 1 and fc,0 : fc,90 = 2.7 … 13.0 … 32.6 : 1 for ρ = 200 … 400 … 600 kg/m³; the ratio of Ec,0 : Em : Et,0 is 1.2 : 1.3 : 1 for ρ = 400 kg/m³. Ashby´s performance indices for minimum weight design rise with the density; the strength-density performance indices are comparable or only slightly lower than that for structural size softwood, whereas the modulus-density performance indices are much lower. The challenge in use of oil palm wood for load-bearing construction products is the low stiffness.

Preparation of β"-Al2O3 electrolytes by freeze-drying and SPS

Na-ionic conductivity and mechanical strength are two important parameters for β"-Al2O3 ceramics used as electrolyte materials. In this study, the ice-templating and freeze-drying processes were used to prepare uniformly porous Al2O3 powder with a certain degree of crystallographic orientation. With the help of spark plasma sintering (SPS) process, solid samples were fabricated from the porous power at a low temperature (1100 °C). Finally, highly conductive and highly strong β"-Al2O3 electrolytes were prepared after the solid samples were subject to further treatment at a high temperature (1600 °C). The scanning electron microscopy (SEM) results indicate that integration of the initial SPS process and further high-temperature sintering treatment have turned the freeze-dried Al2O3 powder to β"-Al2O3 samples whose grain structure is similar to the “brick-bridge-mortar” structure. Regarding such β"-Al2O3 samples, the bending strength parallel to the pressure direction is up to 273 MPa; the degree of crystallographic orientation, 0.25, and the ionic conductivity perpendicular to the pressure direction, 0.239 S cm−1 at 350 °C. Therefore, it can be concluded that the combination of freeze-drying, SPS and an additional high-temperature sintering process has helped generate a structure that improves the ion mobility and bending strength of the β"-Al2O3 ceramic, and thereby improving its strength and ionic conductivity.

The Technological Properties of Oriental Beech (Fagus orientalis Lipsky) Impregnated with Boron Compounds and Natural Materials

Impregnation, drying, and varnishing are performed to increase the usage life of wood material by making it resistant to chemical, physical, and biological agents. The most common wood protection procedures are chemical methods. Therefore, it is essential to develop new impregnation substances that do not harm the environment and human health but are still economically efficient. In this study, oriental beech (Fagus orientalis Lipsky) was impregnated with borax and boric acid in 1%, 3%, and 5% aqueous solutions. Quechua (Caesalpinia spinosa) was also used as a natural impregnation substance. The retention amount of the impregnated samples was examined for the oven-dried density, bending strength, elastic modulus, screw holding strength tests, compression strength parallel to the grain, and Bending strength parallel to the grain. The samples impregnated with borax had higher oven-dried density, bending strength, elasticity modulus in bending, and Bending strength parallel to the grain tests than samples treated with boric acid; however, the screw holding strength tests showed the opposite trend. The screw holding strength was higher in the impregnated samples than in controls. The bending strength, the elasticity modulus in bending, and the Bending strength parallel to the grain were lower in the control samples.

Bending Strength of Sandwich-Type Particleboard Manufactured from Giant Reed (Arundo donax)

Abstract This study evaluated the effects of treatment type of reed (Arundo donax) particles bonded with urea-formaldehyde resin in panels, press closing time, and amount of almond shell powder used as an extender in the glue line had on the modulus of rupture (MOR) of sandwich panels in dry and wet conditions. The differences between the bending strength parallel and perpendicular to the face/back veneer grain in dry (MOR||dry and MOR⊥dry) and wet (MOR||wet and MOR⊥wet) conditions were determined using the t test. According to the results, the selected variables significantly affected the bending strength. The highest dry and wet MORs were obtained by using hot-water–leached particles in the core layer, increasing the press closing time, and increasing the extender content in the glue line. According to the t test, there was a statistically significant difference between the t values of MOR||dry and MOR⊥dry and also between MOR||wet and MOR⊥wet. The maximum MOR||dry and MOR||wet (15.33 and 13.13 N/mm2, respectively) were observed to be higher than those of MOR⊥dry and MOR⊥wet (13.37 and 12.41 N/mm2, respectively).

The study of magnetic properties, coercivity mechanism and bending strength of hot-deformed RE-Fe-B magnets

The effect on mechanical properties and magnetic properties of hot-deformed magnets with different rare earth (RE) content has been investigated. The results show that the optimal comprehensive magnetic properties are obtained at 13.09at% RE. The bending strength parallel to c-axis orientation increases with the increasing of RE content, while that perpendicular to c-axis orientation exhibits decrease. Moreover, the micro magnetic structure was observed and the coercivity mechanism of the hot-deformed magnet sample was discussed.

Determination of Some Physical Attributes for Wooden Construction Elements Strengthened with Woven Wire Fiberglass

This study designed composite wooden construction elements strengthened with woven wire fiberglass netting and determined the technical attributes. Scots pine (Pinus sylvestris L.) was used in wooden layers, and woven wire fiberglass netting was used in intermediate layers. Layers were pressed with polyvinyl acetate (PVAc) D3 and Desmodur-VTKA adhesives to form 7 solid 13-layer laminated composite specimens. Experiments on 95 specimens determined density, bonding strength, bending resistance, and compression strength; solid and solid laminated wooden materials were tested and compared. BS EN 204 and BS EN 205 standards were complied with for bonding strength tests, TS 5497 EN 408 was used for densities, and TS 549 EN 408 was followed for bending resistance and compressive strength. Most factors, except for intermediate layer material in compressive strength and bending resistance tests perpendicular to the glue line, did not cause significant differences. Variables (adhesive, intermediate layer material) used for determining bending strength parallel to the glue line were effective. Polyurethane adhesive increased resistance to bending parallel to the glue line. These composite wooden construction elements supported with woven wire fiberglass netting could be advantageous for applications that require high bending resistance perpendicular to the glue line. However, these composites do not hold a compressive strength advantage.

Reliability Studies on Timber Data from Nigerian Grown Iroko Tree (<i>Chlorophora excelsa</i>) as Bridge Beam Material

This paper provides the results of structural reliability analysis carried out on the data of Nigerian grown Iroko tree (Chlorophora excelsa), to ascertain its structural performance as timber bridge beams. Five pieces of 50mm x 75mm x 3600mm of Nigerian grown Iroko hardwood were bought, seasoned naturally and 200 pieces of samples were prepared for determination of their strength properties, (which include bending strength parallel to grain, tensile strength parallel to grain, compressive strength parallel to grain, compressive strength perpendicular to grain and shear strength parallel to grain) at a moisture content of 18%, in accordance with the British Standard BS 373 of 1957. Statistical analysis was carried out using the strength properties for determination of mean, standard deviation, coefficient of variations, confidence limits and Chi-Square goodness of fits. Structural analysis and design of a timber bridge beam using the determined data from the Nigerian grown Iroko timber, in accordance with BS 5268 were carried out under the Ultimate Limit State of loading (ULSL). Reliability analysis was carried out to ascertain its level of safety using First-Order Reliability Method (FORM). Sensitivity analysis was also carried out by varying the depth of beam, imposed live load, breadth of the beam, unit weight of the Iroko timber, span of the beam as well as the end bearing length. The result revealed that the Nigerian grown Iroko timber is a satisfactory structural material for timber bridge beams at depth of 400mm, breadth of 150mm and span of 5000mm under the ULSL. The probabilities of failure of the Nigerian grown Iroko timber bridge beam in bending, shear, compression and deflection are respectively, under the specified conditions of loading.

Relationships between mechanical properties of oak timber (Quercus robur L.)

AbstractRing-porous hardwoods such as oak are in high demand for furniture-making, cooperage, flooring, and construction. However, evaluating the quality of such timber is difficult and time consuming, and simpler tests are required. Models for predicting as many mechanical properties as possible, based on easier-to-determine mechanical tests, may help. In this study, the hardness, modulus of elasticity, bending, compression, and impact bending strength parallel to grain were tested on defect-free laths obtained from a sample of 42 oak trees. The relationships between the variables were investigated. Three models that relate the resistance to axial compression with bending strength and stiffness (R2>0.55; P<0.01) are proposed for defect-free oak timber. Selection of models mainly depended on the bias, which was highly variable among the models tested. The prediction models proposed in the international standard EN 384:2004 for structural dimension timber are not suitable for small clear wood specimens, especially in very elastic woods. The relative independence of hardness and impact bending strength as regards the other mechanical properties is also demonstrated.

Strength and structure of stems from fast grown Pinus radiata

Segments of living stems from 2-year-old, fast growing Pinus radiata, established on a fertile ex-pasture, were examined in terms of their bending strength parallel to the grain. Stem anatomical and structural variables were examined to identify variables that could explain variation in bending strength. Half of the seedlings were physically supported to minimise the confounding effects of compression wood production in response to environmental stresses. Differences between seedlings and cuttings were examined. Variation in microfibril angle and lignin content was sufficient to account for 81% of the variation in bending strength. A positive correlation between both of these variables and elasticity was evident. Few differences were found to be caused by the support treatment or between seedlings and cuttings. The support treatment resulted in significantly fewer branches in the top most whorl, while cuttings had less branches in this whorl than seedlings.