Bending Strength Values Research Articles

Yeni geliştirilen bir kompozit rezin materyalinin bükülme dayanımının karşılaştırılmalı olarak değerlendirilmesi: Bir in vitro çalışma

Amaç: Bu in vitro çalışmada Mikrohibrid doldurucu içeriği ile yeni geliştirilen bir dental kompozitin mekanik özelliklerinden bükülme dayanımının iki farklı mikrohibrit dolduruculu kompozit materyal ile karşılaştırılmalı olarak değerlendirilmesi amaçlanmıştır.
 Gereç ve Yöntem: Mevcut çalışmada, yeni üretilen bir Üniversal Kompozit (Dolgunn, Himg Seramik ve Medikal Kompozit San.Tic. Ltd.Sti, Türkiye) ile 2 farklı mikrohibrit kompozit (G- aenial Anterior, GC-Japonya ve Filtek Z250 3M, USA) kullanıldı. Her bir dolgu materyalinden 10 adet dikdörtgenler prizması şeklinde (2x2x25 mm boyutunda) örnekler hazırlanarak, instron test cihazında 1 mm/dk hızda bükülme dayanım değerleri ölçüldü. Verilerin istatistiksel analiz için Kruskal-Wallis testi kullanıldı. Tüm testler için istatistiksel anlamlılık düzeyi p=0.05 alındı.
 Bulgular: Tüm test materyalleri arasında bükülme dayanımları açısından istatistiksel olarak anlamlı farklılıklar gözlendi (p

The effect of the use of dimethyloldihydroxyethyleneurea (DMDHEU) chemical in MDF production on the properties of the board

Odun esaslı levhaların hidrofilik malzeme olmalarından dolayı üretimleri sırasında hidrofob özellik kazandıran kimyasal maddeler ile muamele edilmeleri gerekmektedir. Bu çalışmada, orta yoğunluklu lif levha üretiminde çapraz bağlayıcı su itici reçine kimyasalı olan Dimetiloldihidroksietilenüre (DMDHEU) kimyasalı kullanılarak, levha yoğunluğunun ve levha üretim sırasında kimyasalın life farklı ilave edilme şeklinin, levhanın mekanik ve fiziksel özellikleri üzerine etkilerininin araştırılması amaçlanmıştır. Levha üretiminde Melamin Üre Formaldehit tutkalı (1,16 mol, %5 melamin katkılı), sertleştirici olarak amonyum klorür ve %2,2 oranında DMDHEU kimyasalı kullanılmıştır. DMDHEU kimyasalı lifin tutkallama işleminde life tutkallama öncesi (TÖ), tutkallama sonrası (TS) ve tutkal ile birlikte (TB) olmak üzere üç farklı şekilde ilave edilmiştir. DMDHEU kimyasalının ilavesi ile üretilen levhaların su alma ve şişme değerleri kontrol levhasına göre daha düşük olarak bulunmuştur. Üretilen levhaların yoğunluk değerlerinin artması ile su alma ve kalınlığına şişme değerlerinin azalma eğiliminde olduğu tespit edilmiştir. Levhaların mekanik özelliklerinde levha yoğunluğunun artması ile iyileşmeler elde edilmekle birlikte kimyasalın TS ilavesinde ise özellikle eğilme (43,78 N/mm2) ve çekme direnci (1,78 N/mm2) değerlerinde en iyi sonuçlar elde edilmiştir.

Farklı yöntemlerle ısıl işlem uygulanmış ağaç malzemelerde yoğunluk ve eğilme direncinin belirlenmesi

Bu çalışmada, ağaç malzemelerin hava kurusu yoğunluk ve eğilme direnci üzerine farklı yöntem ve sıcaklık koşullarında uygulanan ısıl işlemlerin etkisi analiz edilmiştir. Sarıçam (Pinus silvestris L.) ve kayın (Fagus sylvatica L.) odunu örnekleri ThermoWood, yağlı işlem ve sıcak hava yöntemleri kullanılarak üç farklı sıcaklıkta (170 °C, 190 °C ve 210 °C) ayrı ayrı ısıl işleme tabi tutulmuştur. Deney örneklerinin yoğunluk ve eğilme direnci sırası ile TS 2472 ve TS 2474 esaslarına uyularak belirlenmiştir. Araştırma sonuçlarına göre, ısıl işlem yöntemi ve işlem sıcaklığındaki farklılaşma ahşap örneklerin yoğunluk ve eğilme direnci değerleri üzerinde önemli bulunmuştur. Isıl işlem yöntemi açısından, her iki ağaç türü için en yüksek yoğunluk ve eğilme direnci yağlı ısıl işlem görmüş örneklerde elde edilmiştir. Ayrıca, sıcak hava yöntemine göre ThermoWood yöntemi ile işlem görmüş örneklerde daha yüksek direnç değerleri bulunmuştur. Tüm yöntemler için, ısıl işlem sıcaklığındaki artışa bağlı olarak ahşap örneklerde yoğunluk ve eğilme direnci değerleri azalmıştır. Sıcaklık artışından kaynaklanan yoğunluk ve direnç kayıpları yağlı ısıl işlem yönteminde en az seviyede iken, sıcak hava yönteminde en fazla orana sahiptir.

Effect of freezing temperature on impact bending strength and shore-D hardness of some wood species

Wood is exposed to variable environmental conditions during its use. Low temperature is one of the most important environmental factors affecting the behavior of wood in use. Contrary to other mechanical properties, there are not enough studies on how the impact bending strength is affected during freezing of wood. This study evaluated the effect of various freezing temperatures (-20, -40, -78.5, and -196 °C) on the impact bending strengths of beech (Fagus orientalis Lipsky), Scotch pine (Pinus sylvestris L.), fir (Abies nordmanniana subsp. bornmulleriana), and spruce (Picea orientalis L.) wood in comparison with non-frozen wood (+20 °C). During the freezing, the impact bending strength generally increased in softwood species but decreased in hardwood. The highest drop in impact bending strength value of -30.6% was found at -196 °C for beech wood. For this reason, precautions should be taken when using beech wood at ultra-low temperatures, due to substantial decreases in impact bending strength values. The good impact bending strength properties of the softwood while frozen allows application in low temperature environments.

Effects of Resin Content on Mechanical and Physical Properties of Treated Kenaf Particleboard

Kenaf whole stems were obtained from kenaf plantation located in Chendor, Cherating, Pahang. The stems were cut into small particles with sizes ranging between 0.5 mm to 2.0 mm. Kenaf particles were treated using 2 % NaOH solution. Phenol formaldehyde (PF) adhesive was used to bind the kenaf particles together with resin contents of 8 and 10 %. The objectives of this study were to evaluate the effect of resin content on mechanical and physical properties of treated kenaf particleboard. The boards were cut and tested according to the Malaysian Standard (MS1787:2004) for furniture grade particleboards for use in humid condition. Results showed that the values of modulus of rupture, modulus of elasticity and internal bonding strength increased with an increase in resin content, while thickness swelling and water absorption increased with a decrease in resin content. Kenaf board treated with sodium hydroxide gave the highest value of bending strength and internal bonding strength compared to untreated particleboard which acted as a control board. Although all boards did not achieve the minimum standard values requirement according to the Malaysian standard, kenaf has been proven to have a great potential as raw materials in the particleboard industry. Further studies are needed to improve its properties particularly for exterior applications.

Synthesis and Effect of Nanocellulose Obtained from East Java Kenaf Fiber on Mechanical Properties of Polyurethane Foam Composites as Strong and Lightweight Materials

Cellulose is a fascinating biopolymer and sustainable raw material. Cellulose particles with at least one dimension in the nanoscale are referred to as nanocellulose. Kenaf fiber is a natural fiber used in this study because it has high mechanical properties and strong interface adhesion with polymers so it provides superior properties to other natural fibers. Polyurethane (PU) foam is widely used as a core layer in sandwich composite construction to produce a lightweight material. This study presents a synthesis of cellulose nano-fibrils (CNF) extracted from East Java, Indonesia based kenaf fibers, an analysis of the effect of adding CNF as a filler and a reinforcement in PU foam composites, and a formulation of PU-CNF foam composite that provided the best mechanical properties as strong and lightweight materials in structural applications. The CNF extraction from kenaf fiber started by fiber pre-treatment including alkalization and bleaching, then mechanical treatment with an Ultra Fine Grinder to produce CNF suspension. The weight variations of CNF in PU foam were 0, 3, 5, 7, and 10 wt%. PU-CNF composite fabrication using the in-situ polymerization method. CNF characterization included TEM, XRD, and FT-IR. TEM results on CNF show that the CNF diameter is in the range of 40-70 nm. The functional group from the FT-IR results showed that the pre-treatment process on kenaf fiber was successful in reducing the lignin and hemicellulose content. XRD results showed that the CNF crystallinity was 75.22%. The PU-CNF foam composite characterization included a compressive test, 3-point bending test, and SEM. The PU foam composite with 3 wt% CNF reinforcement is the best composite which has the optimum value from the results of the compression test and the 3-point bending test. The compressive strength value increased by 20.01%, from 236.997 kPa to 284.434 kPa, the compressive modulus value increased by 29.21% from 5.67 MPa to 7.32 MPa, and the 3-point bending strength value increased 28.29% from 572.24 to 734.15 kPa. All the results expected to support that CNF was a potential reinforcement material with a high surface area for a wide variety of applications.

Canola Meal as Raw Material for the Development of Bio-Adhesive for Medium Density Fiberboards (MDFs) and Particleboards Production.

In the context of natural resource scarcity, environmental challenges and human health concerns, the development of alternative solutions becomes crucial to sustainable development. Sustainable and renewable protein-containing materials such as soy or canola have proved to have wood bonding properties comparable to those of synthetic binders. In addition, the availability of canola meal offers a great possibility for the development of bio-adhesives for the wood-based panel industry. Furthermore, direct utilization of canola meal helps to avoid expensive and low-yield protein isolation processes. Using three different solvent solutions (water and 1 mol and 2 mol sodium hydroxide), canola-based bio-adhesives were prepared and used for the production of medium-density fiberboards (with 10 mm thickness and 800 kg/m3 target density) and three-layer particleboards (with 15 mm thickness and 640 kg/m3 target density). The produced boards were tested for their mechanical properties and dimensional stability according to European norms. With the MDFs’ bending strength values above 40 N/mm2 and internal bonding strength greater than 0.5 N/mm2, the results show that there is indeed a possibility to achieve good mechanical properties using canola meal as a binder. The use of NaOH solutions as denaturants, as well as the addition of colasol, helped improve the bonding properties of the boards by 35.49% and 64.52% for 1 mol and 2 mol NaOH solutions, respectively. The obtained results show that the developed canola-based bio-adhesive can compete with conventional ones. However, despite the good mechanical properties of the produced boards, their poor dimensional stability due to the low water resistance of natural proteins suggests further improvement for industrial application.

Investigation of Mechanical Strength and Weight Fraction of Date Palm Fibre Hybrid Composites Reinforced with Polyethylene

Polyethylene, elastomer, and date palm fibre are all readily available, it have an positive impact on growth of new composite materials with desirable features and characteristics. There are many different types of composites, but they all have the same goal: to create a new material with greater qualities than the constituent materials. Date palm fibre was employed to reinforce a composite matrix made of polyethylene (PE) plastic and elastomer. To find out the tensile, impact, and bending strength values of composites by weight fractions of 25% (75:25), 35% (65:35), and 45% (55:45), this research set out to find (55:45). Composites with a weight percentage of 25% (75:25) had less Tensile strength (TS) 1.213 MPa, though mixtures with weightage proportion of 45% (55:45) had the maximum TS of 2.613 MPa. The minimum tensile strain value was discovered in composites with a weight fraction of 25% (75:25), while the maximum tensile strain value was identified in composites with weight fraction of 45 percent (0.0067). (55:45). 45 % (45-55) weight ratio mixture had the minimum impact strength of 45321 kJ/mm2, while the 25 percent (75-25) weight ratio mixture had the maximum impact strength of 17721.41 kJ/mm2. A 25 percent weight fraction (75:25) composite had the lowest bending strength measurement result (1.816 MPa), whereas a 35 percent weight fraction (65:35) composite had the highest measurement result (4.9 MPA) in this category. At 75:25 (75:25), the bending strain of the composite was at its highest, with a value of 0.0216

Effect of spacing on growth, carbon sequestration, and wood quality of 8-year-old clonal teak plantation for sustainable forest teak management in Java Monsoon Forest, Indonesia

Abstract. Rahmawati RB, Widiyatno, Hardiwinoto S, Budiadi, Nugroho WD, Wibowo A, Rodiana D. 2022. Effect of spacing on growth, carbon sequestration, and wood quality of 8-year-old clonal teak plantation for sustainable forest teak management in Java Monsoon Forest. Biodiversitas 23: 4180-4188. Lowland monsoon forest dominated by teak was one of the tropical forest types that can contribute to producing wood production, carbon storage, reduction of emissions, and other ecosystem services. Increasing teak forest productivity could be obtained through teak breeding to get superior teak clones with high diameter growth. Thus, spacing is an important consideration for optimizing the growth, carbon sequestration, and wood properties of teak. However, the study of the growth, carbon sequestration, and wood quality of teak was conducted separately. This research used a selected teak clone aged 8 years with RCBD design with 4 blocks as replications. There were four different spacing as treatments, namely 10 m x 2 m, 8 m x 2 m, 6 m x 2 m, and 3 m x 3 m. The results showed that spacing was a significant effect on DBH, tree height, bole height, carbon sequestration, and volume of teak clones aged 8 years. On the other hand, spacing didn’t significantly affect the physical and mechanical properties of wood. The wood quality test showed that the 6 m x 2 m spacing had high values of bending strength and compressive strength parallel. The highest percentage of heartwood was at a narrow spacing of 6 m x 2 m and did not differ significantly with wide spacing. This indicated that wide spacing was beneficial in terms of teak growth, but wide spacing didn’t significantly affect on wood quality of the teak.

Chemical, Physical, and Mechanical Properties of Belangke Bamboo (Gigantochloa pruriens) and Its Application as a Reinforcing Material in Particleboard Manufacturing.

This study aimed to analyze the basic properties (chemical composition and physical and mechanical properties) of belangke bamboo (Gigantochloa pruriens) and its potential as a particleboard reinforcement material, aimed at increasing the mechanical properties of the boards. The chemical composition was determined by Fourier transform near infrared (NIR) analysis and X-ray diffraction (XRD) analysis. The physical and mechanical properties of bamboo were evaluated following the Japanese standard JIS A 5908 (2003) and the ISO 22157:2004 standard, respectively. The results showed that this bamboo had average lignin, holocellulose, and alpha-cellulose content of 29.78%, 65.13%, and 41.48%, respectively, with a degree of crystallinity of 33.54%. The physical properties of bamboo, including specific gravity, inner and outer diameter shrinkage, and linear shrinkage, were 0.59%, 2.18%, 2.26%, and 0.18%, respectively. Meanwhile, bamboo’s mechanical properties, including compressive strength, shear strength, and tensile strength, were 42.19 MPa, 7.63 MPa, and 163.8 MPa, respectively. Markedly, the addition of belangke bamboo strands as a reinforcing material (surface coating) in particleboards significantly improved the mechanical properties of the boards, increasing the modulus of elasticity (MOE) and bending strength (MOR) values of the fabricated composites by 16 and 3 times.

Microstructural analysis to understand the strength of teak wood using experimental methods

Teak wood is a widely used material for construction applications. However, microstructural and micromechanical behavior is still unknown. This study aims to determine the micromechanical properties of teak wood using an experimental study. For strength prediction, tensile, bending, and compressive testing has been performed on micro samples of teak wood at different loading rates, i.e., 1 mm/min, 0.5 mm/min, and 0.25 mm/min. The scanning electron microscopic (SEM) technique has been adopted for microstructural analysis, and nanoindentation proceeded for local properties. This study shows that the mean value of ultimate tensile, bending, and compressive strength of teak wood is 71.15 MPa, 59.72 MPa, and 39.36 MPa, respectively, at a 1 mm/min loading rate. The tensile and compressive strength decreases with decreasing loading rate, showing direct dependence on loading rate. In contrast, the bending strength does not relate to the loading rate. Therefore, we cannot directly compare the loading rate and bending strength results. Using the SEM technique, the fracture patterns of samples have been studied. Nanoindentation of specimens shows that the cell wall plays a more crucial role in forming good mechanical properties than the material present inside the cell wall.

Evaluation of Physical and Mechanical Properties of Selected Wood Species obtained from Saw Mills in Akure, Nigeria

The strength and sorption properties of selected wood species obtained from saw mills in Akure Nigeria were investigated based on key index properties such as density, bending strength and dimensional stability using appropriate standard experimental techniques. Data obtained from the experimental investigation revealed that the wood species ranged from low density 442.8 kg/m3 for Terminalia superba (Afara), through medium density 464 kg/m3 and 552.8 kg/m3 for Pycnanthus angolensis (Akomu) and Gmelina arborea (Gmelina) respectively, to high density 635.7kg/m3 and 678.2 kg/m3 for Milicia excelsa (Iroko) and Stereospermum acuminatissimum (Omo cedar) respectively. The bending strength values obtained qualified the wood species classification into low bending strength (25 N/mm2 – 75 N/mm2 ) for Afara, Akomu and Gmelina and the medium static bending strength in the range (75 N/mm2 – 125 N/mm2) for Iroko and Omo cedar. Furthermore, results of volumetric shrinkage and swelling are 7.21%: 5.04%, 7.75%: 5.26% and 7.84%: 6.69% for Afara, Akomu and Gmelina respectively while Iroko and Omo cedar recorded 10.95%: 7.84% and 11.08%: 11.08%. These updated results could be useful for wood selection for building construction application; for structural members in roofing, posts and beams.

GL Beams Reinforced with Plywood in the Outer Layer.

Glulam beams are increasingly used in the construction industry because of their high strength and the possibility of using round timber with smaller cross-sections. The load-bearing capacity of beams is strongly related to the quality of the outer layers and, in the case of wood, especially the tension zones. For these reasons, this study decided to replace the outer lamella with tensile plywood. The produced beams were subjected to static bending strength and modulus of elasticity evaluation. It was shown that the best static bending strength values were obtained for beams containing plywood in the tension layer. However, the change in structure in the tension zone of beams made of glued laminated timber results not only in an increase in the load capacity of elements produced in this way but also in a decrease in the range/range of the obtained results of bending strength. This way of modifying the construction of glued laminated beams allows a more rational use of available pine timber.

Pengujian Sifat Fisik dan Mekanik Pada Komposit Papan Partikel Berbahan Dasar Limbah Serbuk Kayu, Serbuk Ban Bekas dan Resin Polyester

Particle board is a board made of wood particles or other particle materials bonded with organic or synthetic adhesives and with the help of one or more elements of heat, pressure, humidity, catalyst and others. particleboard composites made from sawdust, waste tire powder and polyester resin on Bending and Water Absorption Tests. Comparison of composite material composition of particleboard waste wood powder, waste tire powder and polyester resin, namely 30% : 20% : 50%, 40% : 10% : 50%, 45%: 5%: 50% and 50% : 0% : 50%. The test standard is based on SNI 03-2105-2006. The results showed that the greatest bending strength value was obtained at the composition of 50%: 0%: 50% of 186.223 Kgf/cm². and the largest water absorption value was obtained at the composition of 45%: 5%: 50% at 2.581%.Keywords: Bending, Water absorption, Particle board, ,Wood powder, Used tire powder

Highly porous LAS-SiC ceramic with near-zero thermal expansion prepared via aqueous gel-casting combined with adding pore-forming agents

The main problem during preparing high porosity ceramics via aqueous gel-casting is the large drying shrinkage of green bodies. In this work, carbon fibers with high aspect ratio were introduced into aqueous gel-casting processes, which significantly inhibited the drying shrinkage of green bodies by overlapping fibers. At the same time, exhaustible carbon fibers sintered in air also act as sacrificial templates to further improve the porosity. Through the above method, porous LAS/SiC ceramics with high porosity and near-zero expansion were prepared. Drying shrinkage of the green bodies was reduced from 25.2% to 5.7% with the increase of fibers. The porosity of the obtained LAS/SiC ceramic is as high as 76.2%. When the fibers content is 20 vol% and LAS to SiC volume ratio is 6: 4, the composite has maximum value of compression and bending strength (18.2 and 14.0 MPa) and near-zero CTE (0.9 × 10−6 /K).

Mechanical Behaviour of Alkali-Treated Fabric-Reinforced Polymer Matrix Composites

Polyethylene (PE) was used as a composite material to create a fabric containing 40% pineapple, 30% jute, and 30% cotton fibres by weight. The physical characterisation is carried out, like deterioration and water absorption tests. PE-based composites were shown to have a lower water absorption rate when dipped in deionized water to perform an absorption test. Fabric/PE composites decomposed slowly in the soil during the degradation test. Alkali solution of 5 percent, 7 percent, and 9 percent sodium hydroxide by weight for 60 minutes was studied as alkali impact mechanical characteristics: mechanical testing’s like tensile strength and modulus, elongation at break, bending strength, and modulus. Data investigation exposed that the tensile strength and modulus, elongation at break, bending strength, and composite modulus values were 64 MPa and 871 MPa, 23.14 percent, 45 MPa, and 512 MPa. There were tensile strength and modulus, elongation at break, bending strength, and modulus of the neat polyethylene sheet that were 32Mpa and 342 MPa, 79 percent, 22 MPa, and 234 MPa, respectively. Compared to a polyethylene sheet, composite values for tensile strength and modulus, bending strength, and modulus raised by 107%, 156%, 110%, and 115% as a result of fabric reinforcing.

Sedir Ağacının (Cedrus libani) Farklı Kısımlarından Üretilmiş Alçı Esaslı Levhaların Özellikleri. 1. Bölüm. Fiziksel ve Mekanik Özellikler

In this study, it was found that the addition of wood had a reducing effect on water absorption (WA) and thickness swelling (TS) properties in gypsum-based boards. The lowest WA value of 41.56% was found sample prepared with cedrus’s bark/needle mixture (KaI3; 3:2 by weight). It has also been realized that experimental boards made only bark-gypsum (SKa6), cone-gypsum (SKo6) and needle-gypsum (SI6) proportions show Thickness Swelling (TS) values of 33.70%, 21.70% and 18.85%, respectively. However, the surface hardness (Shore D) has usually correlated with wood content but natural weathering negatively effects hardness that lowering from -6.9% (SKa1) to -30.3% (SKa2) in all typse experimental boards. It was found that panels produced with cedrus wood/cone (SKo); cedrus wood/needle (SI) and cedrus cone/needle (KoI) proportions have no higher values than standard Internal Bond (IB) value of 0.28 N/mm2. But the highest IB value of 0.48 N/mm2 was observed for a sample of SKa5 that produced with a ratio of 1:4 by cedrus wood/bark proportions (w/w). Moreover, the highest bending strength (MOR) values of 1.32 N/mm2 were calculated with SKa2 sample that produced with ratio of 4:1 by cedrus wood/bark proportions (w/w). These mechanical properties are probably related to experimental board manufacturing process, which consists of multi stage processing (slushing, soaking, formation, pressing and drying) may effect hindering reinforcement elements to develop the network matrix strength properly.

Effects of Moisture and Direction of Grain on the Thermal Conductivity and Mechanical Properties of Black Alder and Scots Pine

Aim of study: Relationships between moisture content and thermal conductivity and mechanical properties of wood species were examined. Material and methods: Black Alder (Alnus glutinosa L.) and Scots Pine (Pinus sylvestris L.) specimens were used. Thermal conductivity, modulus of rupture, compression strength and impact bending strength values were determined and analyzed. All specimens were examined at 3 different moisture levels which are oven-dry, fiber saturation point (FSP) and completely wet. Main results: The lowest thermal conductivity value was found in the perpendicular to the grain direction of oven dried Black Alder samples as 0.119 W/mK. The highest thermal conductivity value was found in the parallel direction of Scots pine samples with FSP humidity content as 0.340 W/mK. In addition, the thermal conductivity value parallel to the grain is significantly higher than perpendicular one at all three moisture levels. Highlights: While there is a positive linear relationship between the moisture content of the wood and its dynamic bending resistance and thermal conductivity; It was found that there is a negative linear relationship between bending strength and compressive strength value.

Bending Strength Design Method of Phyllostachys edulis Bamboo Based on Classification.

Phyllostachys edulis (P. edulis) bamboo is the most widely distributed and used bamboo species, and it is an ideal building material. With the in-depth implementation of the sustainable development strategy, modern bamboo structures have broad application prospects in green buildings. In order to promote the efficient utilization of bamboo resources and facilitate the design and application of bamboo structures, the bending strength test and classification of P. edulis bamboo were carried out, the factors affecting the reliability were analyzed, and the design values of the bending strength of P. edulis bamboo were proposed based on the reliability analysis. The research results show that dividing P. edulis bamboo into three levels (grade I, grade II, and grade III) can achieve efficient use of P. edulis bamboo resources; 75% fitting data points and normal distribution were used to analyze the reliability of the bending strength of P. edulis bamboo. The analysis of factors affecting reliability makes the calculation of strength design values more reliable. The reliability increases with the increase of the load ratio and the partial factor for resistance. Under the same load ratio and reliability, the partial factor for resistance of the combination of constant load and snow load is the largest, and the partial factor for resistance of the combination of constant load and office building load is the smallest. Under the same load combination and reliability, the partial factor for resistance decreases as the load ratio increases. Under the same load ratio and load combination, the partial factor for resistance of grade III is the largest, and grade I is the smallest. The bending strength design values of grade I, grade II, and grade III are 29.54 MPa, 29.62 MPa, and 30.63 MPa, respectively. This paper innovatively proposed the design values of bending strength of P. edulis bamboo based on classification. The P. edulis bamboo grading method established in this paper and the bending strength design values of P. edulis bamboo proposed can provide references for the design and engineering application of bamboo structures.

The Influence of Alternating Lower and Higher Temperatures on the Bending Characteristics of Glued Norway Spruce (Picea abies (L.) H. Karst.) and European Larch (Larix decidua Mill.) Wood

This article deals with the effect of alternating lower (freezing) and higher (heating) temperatures on the static bending characteristics of glued Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua Mill.) wood. Two types of wood, PUR (polyurethane), and EPI (emulsion polymer isocyanate), were used for the experiment. The thermal loading of glued wood was carried out at temperatures −15 °C/70 °C and −25 °C/70 °C. Static bending characteristics were determined on glued wood samples and compared with the reference samples. Freezing causes an increase in the bending properties of both glued spruce and larch wood. The highest in bending strength was obtained for EPI-glued larch wood subjected to −25 °C/70 °C loading temperature, which is by as much as 20% increase from the reference value. The maximum improvement in the modulus of elasticity was achieved for EPI-glued larch with around 11% increase, although the increased values of bending strength and modulus of elasticity were not significant. The different densities, anatomical structures, and properties of spruce and larch wood can induce varying results between the two wood species.