Tensile Strength Parallel Research Articles

Effect of size on tensile strength parallel to grain of high-performance wood scrimber

With its high strength and excellent dimensional stability, high-performance wood scrimber (HPWS) holds significant promise for applications in load-bearing structures within buildings. However, understanding its behavior concerning size effects, particularly in terms of strength variation with stressed volume dimensions, is essential for establishing design parameters. Despite this importance, research on this aspect remains scarce. To address this gap, this study conducted tension tests on 304 specimens divided into 10 groups, covering a wide range of sizes, with the largest specimen’s volume 162 times that of the smallest. Utilizing the weakest link theory, the study investigated the size effect on tensile strength parallel to grain. Size effect factors were estimated using the shape parameter and slope methods, with discussions on differences related to volume, length, and cross-sectional area factors. It was found that the size effect related to the length and cross-sectional area were 0.0804 and 0.0671, respectively. This difference was due to the load-sharing ability within the cross-section, as the HPWS in tension resembles a net-like structure more than a chain-like structure. The specimens with the smallest cross-section didn’t exhibit the greatest strength. This was because the effects of sawing are particularly severe for very small specimens. This issue requires careful consideration when developing calculation methods. Finally, a calculation method for the tensile strength reduction coefficient, considering size effects, was proposed and demonstrated to align well with experimental findings. This comprehensive analysis serves to advance the structural utilization of HPWS as an innovative building material.

Study on the influence of wood ray morphological characteristics on the tensile strength of wood parallel to grain

The tensile strength of wood parallel to grain is one of the important indicators of wood physical and mechanical properties. Cross-sectional shape possesses a significant effect on the tensile strength parallel to grain, especially for broad-leaved trees with broad wood rays. However the influence of the structural feature of wood rays on the test results, which was commonly ignored. The article focuses on the beech tree with two types of wood rays: broad and narrow, poplar wood with extremely fine wood rays, and dilleniad with extremely rich wood rays. The relationship between the inclination angle and fracture mode of wood rays and the microstructure of wood rays is studied, in order to provide a more accurate scientific basis for determining the tensile strength of wood parallel to grain. The results showed that the inclination angle between the wood ray and the tensile direction has a significant impact on the fracture mode and tensile strength, and the tensile strength parallel to grain without inclination angle is greater than that with inclination angle. Different types of wood rays have a effect on the coefficient of variation of the tensile strength parallel to grain of the specimen. Under the same inclination angle, the Pearson correlation between the wood ray parenchyma ratio and the tensile strength parallel to grain is significantly negative at the 0.01 level (double tailed) or 0.05 level (double tailed). Besides, as the wood ray parenchyma ratio gradually increases, the overall tensile strength of wood parallel to grain shows a downward trend. The fracture surface morphology characteristics of specimens with different fracture modes are different.

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.

Enhancing flame retardancy and antibacterial properties of wood veneer by promoting crosslinking in metal-organic framework structures

Decorative veneer, rotary cut from wood, serving as the outermost layer of decorative plates and is exposed to potential risks of fire hazards and bacterial growth. In this study, following the principle of eco-friendly and cost-effective, the polyamino polyether methylene phosphonate (PAPEMP) and magnesium chloride (MgCl2) were sequentially impregnated into the veneer, and then the alkaline environment was employed to facilitate the complexation, leading to the formation of cross-linked chains within the porous wood structure. Consequently, the modified wood veneer, endowed with exceptional flame retardancy, smoke suppression, antibacterial properties, and good wettability was successfully achieved. Through optimization in an alkaline environment, the modified decorative veneer exhibits a remarkable increase in limiting oxygen index from 19.7% in the pure veneer to 36.9%, coupled with a significant reduction of 19.38% in total heat release and 65.22% in total smoke release compared to the pure veneer. Additionally, the peak mass loss rate (PLMR) of the modified veneer was 66.41% lower than that of the pure veneer, and the char residue increased to 46.1%, representing a 149.19% improvement over the pure veneer. Compared with pure veneer, the wettability of modified veneer increased by 37.93%. Additionally, the tensile strength parallel to the grain of the modified veneer was enhanced by 22.09% compared to the veneer without NaOH solution treatment, and exhibits strong inhibitory effects on colony reproduction. The developed flame-retardant and antibacterial treatment processes for decorative veneers offer a novel and environmentally friendly method for utilizing precious tree veneers, suitable for a variety of precious woods, and successfully applied to decorative wooden doors and wooden fire-resistant doors.

Influence of Moisture Content on Physical and Mechanical Properties of Chinese Ash Bolts for Anchoring Earthen Sites

Abstract Chinese ash bolts are extensively utilized for anchoring earthen sites in China, but their physical and mechanical properties are influenced by changes in moisture content during the grout curing process. This study reveals significant effects on compressive strength parallel to the grain and flexural strength, with a comparatively lower influence on tensile strength parallel to the grain. As moisture content increases, the failure mode shifts from fiber fracture to inter-fiber destruction, resulting in a transition from brittleness to elastoplasticity in the bolts’ properties. Additionally, we observed that the diameter of the samples has a less pronounced effect on mechanical strength and modulus compared to moisture content, though it notably enhances resistance to deformation. Scanning electron microscopy images show interlocking textures within the wooden fibers, effectively enhancing the strength and toughness of the bolts. Importantly, this research presents quantitative results: Chinese ash bolts exhibit a natural density range of 0.65 to 0.78 g/cm3 and a saturation moisture content spanning from 93.15 to 114.15 %. Furthermore, in their natural state, these bolts display remarkable tensile strength (126.56 MPa), compressive strength (55.91 MPa), and bending strength (106.34 MPa). This study highlights the critical significance of carefully choosing the most suitable bolt diameters to fortify resistance against deformation. The concrete data provided contribute significantly to improving conservation practices for earthen sites.

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.

Ascent and emplacement controls of mafic magmas in the mid crust − evidence from 3D modelling of basic bodies of the Koperberg Suite, Namaqualand

Abstract The 3D modelling of basic bodies of the Koperberg Suite (1060 to 1030 Ma) and their wall rocks from Narrap Mine illustrates the distribution, geometries and, by implication, processes that determined the ascent and emplacement of the mantle-derived mafic magmas into the partially-molten, mid-crustal granite-gneiss sequence of the Okiep Copper District in Namaqualand. The lens-like, discontinuous geometry of basic bodies suggests the transfer of the mafic magmas as self-contained, buoyancy-driven hydrofractures. The presence of both shallowly-dipping, foliation-parallel sills and subvertical lenses in zones of steep foliation development, so-called steep structures, indicates an emplacement of the mafic magmas under low deviatoric stresses and irrespective of the regional stress field. Instead, the emplacement of the mafic magmas parallel to pre-existing anisotropies (tectonic fabrics or lithological contacts) highlights those differences in tensile strength and fracture toughness parallel to or across anisotropies determined the propagation of the magmas. This also accounts for the common occurrence of basic bodies in steep structures in which the vertical gneissosity promoted the buoyancy-driven ascent of the mafic magmas. On a regional scale, the mechanical stratification of the subhorizontal, sheet-like granite gneisses and interlayered metasediments exerted important controls on the ascent of Koperberg Suite magmas. The preferential emplacement of basic bodies in schist and gneiss units suggests that the lower rigidity of the ductile wall rocks facilitated magma emplacement through a combination of viscous wall-rock deformation and fracture blunting that led to the arrest of the magma-filled hydrofractures. Multiple intrusive relationships of successively emplaced magma batches suggest that later magmas reutilised earlier established magma pathways, particularly in steep structures. High-rigidity lithologies, such as the massive Springbok Quartzite, in contrast, only allowed for smaller fracture apertures and limited dilation, resulting in the pinching of basic bodies and rather stringer-like geometries. It is conceivable that the higher fracture toughness of the quartzite may also have prevented propagation of the mafic magmas through the Springbok Quartzite and, instead, led to the ponding of basic bodies below the metasediments. The geometry and structural and lithological controls of basic bodies at Narrap Mine are similar to Koperberg Suite intrusions documented from many of the other mine workings in the Okiep Copper District. This suggests similar underlying emplacement controls of the cupriferous rocks, which can be extrapolated on a regional scale and that may guide exploration.

Behavioral change in physical, anatomical, and mechanical characteristics of thermally treated Pinus roxburghii wood

Thermal treatment of pine wood was carried out at 80, 120, 160, and 200 °C for 2, 4, and 6 hours. The highest mean values were, for specific gravity (0.492), moisture content (29.1%), and maximum moisture content (191%), whereas the lowest mean values were for specific gravity (0.418), moisture content (1.20%), and maximum moisture content (127%). The maximum mean values were for shrinkage in longitudinal plane (0.42%), radial plane (4.63%), volumetric shrinkage (9.28%), and maximum mean value tangential plane (3.67%). The minimum mean values were for shrinkage in longitudinal plane (0.04%), radial plane (2.22%), tangential plane (1.55%), and volumetric shrinkage (4.88%). Maximum mean values were for swelling in longitudinal (0.41%), radial (5.22%), and tangential plane (3.15%) and maximum mean volumetric swelling (7.71%), while minimum mean values were for swelling in longitudinal plane (0.08%), radial plane (2.26%), and tangential plane (1.29%) and minimum mean volumetric swelling (3.15%). The highest mean values were for tensile strength (57.3 MPa) and compression parallel to the grain (50.3 MPa), the maximum mean value of bending strength (84 MPa) and compression strength perpendicular to grain (27 MPa), whereas the lowest values were for tensile strength (42.7 MPa), bending strength (7.33 MPa), compression parallel to the grain (7.33 MPa) and compression strength perpendicular to grain (12.3 MPa).

Effect of softening duration on physical, mechanical and microstructural properties of flattened densified Bambusa bambos

The half-split Bambusa bambos culms were flattened after subjecting them to different steaming durations in the range of 20–40 min. The flattened bamboos from bottom, middle and top sections were further subjected to the densification process using a hot press. Various physical and mechanical properties of the flattened and densified bamboo (FDB) were evaluated and compared with control. Analytical techniques such as scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were applied to study the microstructure and chemical changes due to flattening and densification. The results showed that softening duration had significant effect on all the properties of the FDB. The flattened sheets prepared from the bottom, middle and top portions of bamboo showed different properties. The density of the FDB was observed to increase significantly compared to untreated bamboo. The significant density improvements lead to relatively uniform distribution of the vascular bundles through the radial direction of the culm wall. Although the water absorption of the FDB boards was significantly reduced compared to control, no improvement was observed in the dimensional stability after water submersion for 24 h. With the increase in softening duration, various mechanical properties such as flexural strength, flexural stiffness and tensile strength parallel to fibre direction of FDB were improved significantly. The SEM observations showed that the microstructure of parenchyma and vessel elements changed significantly while fibre microstructure was undisturbed. FTIR analysis showed that hemicellulose content was slightly reduced while other chemical constituents of bamboo were not much affected. The crystallinity of the bamboo was found to be increased after flattening and densification leading to improvement in strength properties. These findings may be of practical importance for efficient utilization of bamboo in production of value-added FDB composites.

Fabrication of a bamboo-based glulam based on reconstitution unit innovation: Mechanical property investigation and carbon footprint evaluation

The development of high-quality, large format bamboo structural materials is a hot spot. Here, we fabricated a flattened bamboo board (FB) with a large size, which was further laminated and lengthened to prepare FB-based glulam. Two kinds of FBs were fabricated based on different flattening methods: notched-FB and smooth-FB. Compared with the notched-FBs, the modulus of rupture (MOR) and modulus of elastic (MOE) values of smooth-FBs which were previously softened at 175 °C increased by 9.2% and 7.7%, respectively. The FB-based laminated boards whose middle bonding layer is yellow surface to yellow surface show the best mechanical properties among all the three candidates, with dry shear strength, compressive strength parallel to grain, tensile strength parallel to grain, MOR and MOE values of 20.7 MPa, 52.5 MPa, 115.6 MPa, 119.6 MPa and 14.2 GPa, respectively. Finally, two lengthening methods of horizontal and vertical finger connections were introduced to enlarge the size. The results indicate that the FB-based glulam with extension interfaces near to the two terminal points of each laminated boards exhibits better bending resistance with a MOR value as large as 95.9 MPa, being attributed to the corresponding distributed stress and extended the stress transmission distance. The FB-based glulam is proved to be a carbon-neutral product with a carbon footprint value of − 1.12 kg CO2/t. This work is the first time to use FBs as reconstituted units for bamboo glulam. We hope to discuss the effects of changes in process parameters and methods at different manufacturing stages on the physical and mechanical properties of the material, thus providing an experimental and theoretical basis for the application of FBs in the field of large-scale bamboo-based structural materials and also broadening the application field of bamboo with high added value.

Through-thickness distribution of bamboo tensile strength parallel to fibres

A tensile test program of Moso bamboo samples was carried out in order to obtain information on the radial distribution of elastic and strength properties. In accordance with previous studies, the elastic modulus and the tensile strength were found to increase outwards in the radial direction. This spatial dependence was compared with the distribution of the fibre content of the layers and found excellent correlation suggesting that the fibres are the main load bearing components. The fibre content was quantified using regression analysis in the radial direction as 0.1 (inner layer), 0.19 (middle-1 layer), 0.28 (middle-2 layer) and 0.44 (outer layer). The Rule of Mixture theory allowed the estimation of the elastic modulus and the tensile strength of the main individual components, the fibres and the parenchyma matrix.Article HighlightsRadial distribution of bamboo fibres across the culm wall and stiffness properties obtained from tensile test parallel to fibres were compared.The radial distribution of bamboo fibres was analysed in layers using image analysis software.The tensile failure mechanisms of bamboo samples were identified and found to depend on fibre content.

A study on some physical and mechanical properties of molded thermal insulation materials produced from perlite and boric acid added forestry by-products

ABSTRACT The tree bark and cones are either burned or left in the forest. In both cases, it causes both environmental problems and a significant loss of economic potential. In this study, some physical and mechanical properties of molded thermal insulation materials produced from natural raw materials were investigated experimentally. In this context, 15 types of sandwich panel materials containing honeycomb-shaped core were produced from pine (Pinus brutia Ten.) bark and cones. The mean moisture content, density, compressive strength, tensile strength perpendicular to the surface, tensile strength parallel to the surface, and dimensional stability values of the materials were 10.6%, 269.717 kg/m3, 0.493.06 N/mm2, 0.011 N/mm2, 0.150 N/mm2 and −0.156%, −0.054%, 0.942%, respectively. According to the results, it was determined that the increase in particle size and perlite ratio in the materials produced from the bark decreased the density. Moreover, it was found that the particle size-moisture content relationship and the perlite ratio-moisture content relationship varied in the materials containing bark and cones, that the mechanical properties were higher in the materials containing cones, and that the dimensional stability did not show a regular change.

SOME PHYSICAL AND MECHANICAL PROPERTIES OF KATHBADAM (Terminalia catappa Linn.) WOOD OF BANGLADESH

The present study was undertaken to represent mainly some strength properties of kathbadam (Terminalia catappa Linn.) wood of Bangladesh along with finding out some relevant physical properties of the same. The research works were carried out following standard test methods comparing the findings with those of standard Chittagong teak (Tectona grandis L.f.) reported earlier. The longitudinal, radial, tangential and volumetric shrinkages of T. catappa wood from green to oven-dry conditions were found 0.64%, 2.71%, 5.08% and 8.43% respectively. The specific gravity of the wood species based on oven-dry weight by green volume and oven-dry weight by oven-dry volume were found 0.46 and 0.52 respectively. The green moisture content of T. catappa wood was found 92.51%. Regarding green mechanical properties, the fibre stress at elastic limit and modulus of rupture was found 408.61 and 666.16 kg cm-2 respectively. Similarly the revealed green compressive strength parallel to grain at elastic limit and at maximum load was 210.54 and 273.74 kg cm-2 respectively. The green tensile strength parallel to grain at maximum load was revealed 438.41 kg cm-2. At the same moisture conditions the screw withdrawal capacity was determined 187.16 kg at sawn face and 170.53 at edge. All these properties of T. catappa wood were found relatively and reasonably lower than those of Chittagong teak.

Impact of the Heat Treatment Duration on Color and Selected Mechanical and Chemical Properties of Scots Pine Wood.

The aim of this study was to assess the effect of the duration of heat treatment on changes in the color, as well as the chemical and mechanical properties of Scots pine sapwood. An important element of the research was to obtain the assumed temperature in the entire volume of samples. Quantitative changes in color and its components were recorded, while mechanical properties were determined in tests of compressive strength parallel and perpendicular to the grain, longitudinal tensile strength and modulus of elasticity and impact strength. The novelty of the research was to determine the above-mentioned parameters for twin samples with identical moisture contents. Chemical analyses were conducted on heat-treated wood that was subjected to heat treatment at 220 °C for a period from 1 to 8 h. Extension of the heat treatment duration resulted in the increasing darkening of the wood, as well as a further reduction in the impact strength and tensile strength parallel to the grain by approx. 40 and 50%, respectively, compared to the control wood, but also compared to heat-treated wood for a shorter treatment duration. The heat treatment of wood caused changes in the contents of the wood components, as well as the elemental composition in the heat-treated wood, compared to the control pine. The changes in the structure of the heat-treated wood were confirmed by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Observed quantitative changes in the main wood components, its structural changes, as well as wood decomposition and increased crystallinity of cellulose explain significant changes in both the mechanical properties and the color of heat-treated wood.

Impregnation analysis of phenol-formaldehyde resin on sengon wood to explore the potential of sengon wood as construction material

The current climate emergency is a growing concern, while construction activities are one of the biggest causes. Therefore, research is needed that leads to the application of construction with environmentally friendly materials such as wood. In this study, the wood used is sengon wood (Falcataria moluccana) because it has very abundant availability. However, sengon wood has low strength and durability, so treatment is needed to improve the quality of sengon wood so that its potential can be utilized. There were seven test variables, namely untreated sengon sawn wood, vacuum pressure impregnation with 5%, 10%, 15% phenol-formaldehyde (PF) resin solution, cold immersion impregnation with 5%, 10%, and 15% PF. The results of this study showed that treatment of cold immersion concentrate PF 10% increases tensile strength parallel to fibre up to 91.5%, the biggest increase in value against one of the mechanical properties, but to improve the mechanical properties of the highest average is variable B with vacuum pressure treatment of concentrates 5% with the increase up to 9.1%. Regardless of the comparison of these variables, that the value of the mechanical properties of sengon wood as sawn wood without treatment already has the potential to be used as a construction material compared to the value of the lowest strength class of construction sawn wood material. According to this research, the average density of sengon wood is about 300 kg/m3 which tends to be categorized as a lightweight construction material, where the concept of a lightweight structure can trigger increased innovation in creating more varied architectural and structural designs.

Comparative Study on Clear Specimen Strength and Member Strength of Side‐Pressure Laminated Bamboo

Side‐pressure laminated bamboo (LB) made from heat‐modified, fast‐growing bamboo is introduced in this document. As a relatively new type of bamboo composite fabricated by bamboo strips, side‐pressure LB has some favorable mechanical properties, such as thermal insulation, light mass, high strength, and earthquake resistance. To promote the application of side‐pressure LB in structural engineering, according to the test standards for timber, the mechanical properties of bamboo, including tensile strength parallel to the grain, compressive strength parallel to the grain, bending strength and bending modulus, and shear strength parallel to the grain, were obtained by testing clear bamboo. Meanwhile, the bending and shear tests were performed on full‐sized beams of side‐pressure LB. Comparing the strength of clear bamboo and full‐sized bamboo beams under bending and shear, explore the effect of size on bending and shear strength. The results demonstrate that the size effect has a significant influence on the bending strength, and the bending strength decreases clearly with the increase of the span of member; the shear strength is mainly affected by the shear area and decreases with the increase of the shear area. Based on the measured indicators of shear strength, a formula suitable for converting the shear strength of clear bamboo to full‐sized bamboo beam is proposed. And the recommended design strengths of bamboo are given by using the limit state method, which provides a design basis for the engineering application of bamboo.

Design strengths of bamboo based on reliability analysis

To reasonably determine the design strengths of bamboo, in this work, the tensile strength parallel to particles, compressive strength parallel to particles, tensile strength perpendicular to particles, and compressive strength perpendicular to particles of bamboo were systematically investigated. The tensile strength parallel to the grain of the bamboo material was the highest, and it reached the minimum when perpendicular to the grain. The influence of the functional form of the probability distribution and data points for fitting on the reliability was evaluated by the first and second-moment checking point method. It was recommended to use the fitting results of the first 15% strength data and the 2-P-Weibull probability distribution model to determine the design values of the bamboo strength. On the basis of reliability analysis, the variation rule of reliability index and resistance coefficient of bamboo under different load combination types and load-effect ratios was calculated. The optimum partial resistance coefficient of the bamboo was determined by minimising the sum of squares of error, and the design strength of the bamboo was determined accordingly.

Bearing Capacity and Mechanical Behavior of an Innovative Bamboo Fiber-Reinforced Polymer Tendon with U-Head.

The development of steel in engineering structures or components faces the problems of high cost and high carbon emission, which demands new materials used as reinforcement to be proposed and applied. Bamboo is a green and renewable natural material, and has higher tensile strength parallel to grain compared to wood. Based on the excellent mechanical properties in the parallel-to-grain direction of bamboo fiber, this paper proposed an innovative bamboo fiber-reinforced polymer tendon with U-head (BFRP tendon). To analyze the tension capacity and mechanical behavior of the BFRP tendon, the thin-shell model and thick-shell model have been proposed in succession. Both models were compared with the results of tensile test and good agreement was achieved in the stress distribution and the ultimate load. The tension capacity of the BFRP tendon has been proved to be reliable, which can give full play to the advantages of bamboo fiber.

Effect of Bamboo Nodes on the Mechanical Properties of P. edulis (Phyllostachys edulis) Bamboo

In the context of global sustainable development, the use of natural and renewable bamboo as a building material is of great significance for building engineering. As an important part of bamboo, there is still a lack of systematic research on the effect of bamboo nodes on the mechanical properties of bamboo. In this paper, compression parallel to the grain of the bamboo, bending, tensile parallel to the grain, shear parallel to the grain, compression perpendicular to the grain and tensile perpendicular to the grain tests of an entire bamboo culm of P. edulis bamboo were carried out, and the effects of bamboo nodes on moisture content, bearing capacity and mechanical properties were analyzed. The relationship between the mechanical properties and standardized parameters of the node and internode specimens was established. A conversion method of mechanical properties of the same test type was proposed, and a conversion method among different mechanical properties was proposed. The bamboo was graded by tensile strength parallel to the grain. The results show that bamboo nodes have an obvious effect on the moisture content. Bamboo nodes have different effects on the bearing capacity and mechanical properties of different types of specimens. The mechanical properties of P. edulis bamboo can be predicted by the relationship between the mechanical properties and the standardized parameters and the mechanical property conversion method. The strength classification of P. edulis bamboo can be predicted by standardized parameters.

FLAT-PRESSED WOOD PLASTIC COMPOSITES FROM COMMUNITY FOREST WOOD BARK AND RECYCLED POLYPROPYLENE: THE EFFECT OF PRESSING TEMPERATURE ON THE PHYSICAL, MECHANICAL, AND MORPHOLOGICAL PROPERTIES

The article describes a new idea related to the use of wood bark powder as a filler material in the production of wood plastic composites using flat-pressed method, based on its thermal stability and abundant availability, enabling replacing wood powder, which has been widely used. This research aims to study the effect of temperature on the physical, mechanical, and morphological properties of flat-pressed wood plastic composites made from Gmelina arborea bark and recycled polypropylene. A 40:60 mesh (5% moisture content) of G. arborea bark powder was mixed with recycled polypropylene (RPP) pellets with a weight ratio of 40:60 and a maleic anhydride (MAH) modifier as much as 5% of the weight of the RPP was added. Mixing the ingredients is done in a rotating blender for 15 minutes at a speed of 80 rpm until homogeneous. The mixture was heated at 175oC until the RPP pellets were completely melted and then cooled at room temperature. After that, the material mixture was made into powder and filtered, and then moulded in a steel plate mould at temperatures of 160, 165, and 170oC under a pressure of 30 kg/cm2 for 4 minutes with a target density of 1 g/cm3. Physical properties including density, moisture content, water absorption, thickness swelling, and volume shrinkage according to ASTM D570 standard were determined. Mechanical properties, such as modulus of elasticity (MOE) and modulus of rapture (MOR), referring to ASTM D7031 standard, and tensile strength parallel to panel length, referring to ASTM D638 standard, were also evaluated. In addition, composite morphology was also studied using scanning electron microscopy (SEM). The results showed that the increasing of pressing temperature had a significant effect on the improvement of moisture content, water absorption, thickness swelling, volume shrinkage, and MOR. MOR value increased by 34.12% when the pressing temperature increased form 160oC up to 170oC. Our method allows improving the physical and mechanical properties of wood bark plastic composites based on a pressing temperature of 170oC.