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Physical and Mechanical Properties of Wood- and Bamboo-Based Materials

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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Wood Science and Forest Products".

Deadline for manuscript submissions: closed (15 July 2024) | Viewed by 7265

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Special Issue Editors

Dr. Xuehua Wang

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Guest Editor

College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing 210037, China
Interests: physical and mechanical properties; forming processing; modification and application

Prof. Dr. Yan Wu

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Guest Editor

College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing 210037, China
Interests: green manufacturing of home materials; water-based wood coatings and green coating; new wooden home materials

Special Issue Information

Dear Colleagues,

Wood and bamboo represent significant biomass materials with an extensive historical legacy of application in human civilization. Products derived from wood and bamboo find widespread utility across sectors, including construction, home furnishings, transportation and other realms, intimately intertwined with human production and daily existence. The specific performance requisites of wood- and bamboo-based materials are contingent upon their designated applications. These materials offer a series of merits, encompassing environmental sustainability, a remarkable strength-to-weight ratio, commendable seismic resilience, aesthetic appeal and facilitative processing characteristics, etc. Simultaneously, inherent to the nature of biomass materials, wood- and bamboo-based materials are not devoid of drawbacks, including variable dimensional stability, limited fire resistance and susceptibility to degradation.

Acknowledging the distinctive attributes of wood and bamboo, alongside the distinctive usage demands imposed by diverse contexts, various techniques, such as lamination gluing, reagent impregnation and softening treatments, have been employed for enhancement. These treatments are employed to achieve heightened dimensional stability, augmented strength, superior molding capabilities and enhanced processing performance, thereby broadening the spectrum of potential applications and prolonging their functional lifespan. In doing so, these endeavors leverage the carbon sequestration potential of wood and bamboo, contributing to the reduction in carbon dioxide emissions.

This Special Issue is poised to provide an avenue for scholars and stakeholders to remain at the vanguard of advancements in the field of the physical and mechanical properties of wood and bamboo. Those with an interest in the physical and mechanical attributes of wood and bamboo are cordially invited to collaborate and disseminate their latest accomplishments in this domain.

Dr. Xuehua Wang
Prof. Dr. Yan Wu
Guest Editors

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Keywords

wood- and bamboo-based materials
physical and mechanical properties
modification and application
microstructure

Published Papers (10 papers)

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Research

15 pages, 5697 KiB

Open AccessArticle

The Novel Applications of Bionic Design Based on the Natural Structural Characteristics of Bamboo

by Siyang Ji, Qunying Mou, Ting Li, Xiazhen Li, Zhiyong Cai and Xianjun Li

Forests 2024, 15(7), 1205; https://doi.org/10.3390/f15071205 - 12 Jul 2024

Viewed by 368

Abstract

The unique composite gradient structure of bamboo has made it widely recognized as an extremely efficient natural structure and material, endowing it with exceptional flexibility and resilience. This enabled bamboo to withstand the forces of wind and snow without fracturing. In this paper, the inherent structural characteristics of bamboo were examined in order to extract its biological advantages through experimental methods. Then, the structural characteristics of bamboo in its vertical and radial directions served as the respective inspiration for two bionic applications, which were further analyzed and optimized using finite element analysis to accurately evaluate their bearing capacities. It can be found that the density of vascular bundles increased proportionally with the height of the bamboo stem, while the circumference exhibited a linear decrease. The wall thickness of the bamboo decreased and stabilized after reaching a height of 10 m. The distribution of nodes exhibited a nearly symmetrical pattern from the base to the top of the bamboo stem. The tapering of the bamboo culm exhibited a non-linear pattern with height, characterized by an initial decrease followed by a slight increase ranging from 0.004 to 0.010. The vascular bundles in bamboo exhibited a functional gradient distribution, which had a 6:3:2 distribution ratio of vascular bundles in the wall’s dense, transition, and sparse areas, respectively. The bionic cantilever beam incorporated characteristics of a hollow structure, a non-uniform distribution of nodes, and a certain amount of tapering, which effectively enhanced its flexural performance compared to the traditional ones. The thin-wall tube, featuring a “dendritic” partial pressure structure, demonstrated exceptional lateral compressive performance in transverse compression, particularly when the tube incorporated a gradient distribution of partition numbers and layer spacing. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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14 pages, 6319 KiB

Open AccessArticle

Optimizing the Preparation Process of Bamboo Scrimber with Bamboo Waste Bio-Oil Phenolic Resin Using Response Surface Methodology

by Ying Li, Chunmiao Li, Xueyong Ren, Fuming Chen and Linbi Chen

Forests 2024, 15(7), 1173; https://doi.org/10.3390/f15071173 - 5 Jul 2024

Viewed by 449

Abstract

Bamboo scrimber is a new type of biomass fiber-based composite material with broad application. In this study, self-developed bio-oil phenolic resin (BPF) was used to prepare bamboo scrimber. The effects of hot-pressing temperature, hot-pressing time, and BPF resin solid content on the modulus of rupture (MOR) and modulus of elasticity (MOE) were systematically investigated through single-factor experiments and response surface methodology (RSM). According to the Box-Behnken design (BBD) experiment of the RSM, the effects of all three factors on MOR and MOE are significant. The effects of the main factors affecting the MOR and MOE decreased in the order of resin solid content, hot-pressing temperature, and hot-pressing time. Based on BBD, the optimal conditions for the preparation of bamboo scrimber were determined as follows: a hot-pressing temperature of 150 °C, a hot-pressing time of 27.5 min, and a resin solid content of 29%. Under these conditions, the MOR is 150.05 MPa and the MOE is 12,802 MPa, which are close to the theoretical values, indicating that the optimization results are credible. This study helps to promote the full utilization of bamboo components and provides a reference for the development of high-quality bamboo scrimber. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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13 pages, 5018 KiB

Open AccessArticle

Consolidation and Dehydration Effects of Mildly Degraded Wood from Luoyang Canal No. 1 Ancient Ship

by Weiwei Yang, Wanrong Ma, Xinyou Liu and Wei Wang

Forests 2024, 15(7), 1089; https://doi.org/10.3390/f15071089 - 23 Jun 2024

Viewed by 455

Abstract

To ensure the conservation of waterlogged archaeological wood, sustainable, safe, and effective methods must be implemented, with consolidation and dehydration being crucial for long-term preservation to maintain dimensional stability and structural integrity. This study compares the permeability of 45% methyltrimethoxysilane (MTMS) and 45% trehalose solutions to evaluate the dimensional changes, hygroscopicity, and mechanical properties of treated wood. Since the collected samples (from an ancient ship, Luoyang Canal No. 1) were mildly degraded, the drying method had a slight impact on the properties of archaeological wood. Consolidated with trehalose and MTMS agents, the longitudinal compressive strength of the waterlogged wood’s cell walls increased by 66.8% and 23.5%, respectively. Trehalose proved to be more advantageous in filling pores and reducing overall shrinkage, while MTMS significantly reduced the hygroscopicity and surface hydrophilicity of the wood substance. Overall, the MTMS treatment has a smaller effect on the appearance of samples, making it more suitable for the consolidation of mildly degraded waterlogged archaeological wood. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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14 pages, 5820 KiB

Open AccessArticle

The Gradient Variation of Location Distribution, Cross-Section Area, and Mechanical Properties of Moso Bamboo Vascular Bundles along the Radial Direction

by Hongbo Li, Qipeng Zhu, Pengchen Lu, Xi Chen and Yu Xian

Forests 2024, 15(6), 1023; https://doi.org/10.3390/f15061023 - 13 Jun 2024

Viewed by 595

Abstract

Bamboo is a typical natural fiber-reinforced composite with excellent mechanical properties, which are determined by its special micro-structure. As the reinforcing phase, the vascular bundles play a central role in the control of the mechanical properties of bamboo macro-structure. To find the exact gradient variation of the mechanical properties of these continuously distributed vascular bundles within the bamboo culm, 4-year-old Moso bamboo was chosen to investigate the variation of locate-distribution, cross-section area, and mechanical properties of single vascular bundles along the longitudinal and radial directions with respect to their location from the base, middle, and top sections of bamboo culm, respectively. It shows that the spatial distribution of vascular bundles along the column is distributed exponentially from the inside to the outside of the culm. The cross-section area of the vascular bundles decreased exponentially from the inside to the outside along the radial direction. All the vascular bundles were then carefully separated from bamboo strips and tested via the tensile tests. Test results show that the longitudinal tensile strengths of vascular bundles ranged from 180.44 to 774.10 MPa, and the longitudinal Young’s modulus ranged from 9.00 to 44.76 GPa. The tensile strength of vascular bundles at the outer side was three times higher than that of the inner side, while Young’s modulus at the outer side was three to four times higher than that of the inner side. For all three height positions, the strengths and Young’s modulus of vascular bundles are all exponentially increased from the inner side to the outer side along the radial direction. This work will provide a basis for the highly processed product’s application of bamboo resources and a reference for further study on the trans-scale analysis of the mechanical properties of bamboo. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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11 pages, 14843 KiB

Open AccessArticle

Evaluation of Deterioration Degree of Archaeological Wood from Luoyang Canal No. 1 Ancient Ship

by Weiwei Yang, Wanrong Ma and Xinyou Liu

Forests 2024, 15(6), 963; https://doi.org/10.3390/f15060963 - 31 May 2024

Cited by 1 | Viewed by 408

Abstract

This study provides a detailed investigation of archaeological wood samples from the Luoyang Canal No. 1 site, focusing on wood species identification, physical properties, mechanical property analyses, and morphological examination. The identified wood species, belonging to the Ulmus genus, exhibited a 43% decline in compressive strength in waterlogged environments. Further, the wood exhibited increased moisture content, higher porosity, reduced basic density, and elevated shrinkage rates, indicating a mild level of degradation. X-ray diffraction was employed for the observation of cellulose structure, and Fourier transform infrared spectroscopy (FT-IR) demonstrated significant removal of cellulose and hemicellulose components. These findings emphasize the importance of understanding wood degradation mechanisms to evaluate structural integrity and durability in guiding the development of effective preservation strategies for archaeological wood artifacts. Continued research and conservation are crucial to deepen our knowledge of wood deterioration processes and enhance the implementation of preservation techniques. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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13 pages, 9668 KiB

Open AccessArticle

Highly Mechanical Strength, Flexible and Stretchable Wood-Based Elastomers without Chemical Cross-Linking

by Yongyue Zhang, Jiayao Li, Yun Lu and Jiangtao Shi

Forests 2024, 15(5), 836; https://doi.org/10.3390/f15050836 - 10 May 2024

Viewed by 690

Abstract

Wood exhibits a limited elastic deformation capacity under external forces due to its small range of elastic limit, which restricts its widespread use as an elastic material. This study presents the development of a stretchable wood-based elastomer (SWE) that is highly mechanical and flexible, achieved without the use of chemical cross-linking. Balsa wood was utilized as a raw material, which was chemically pretreated to remove the majority of the lignin and create a more abundant pore structure, while exposing the active hydroxyl groups on the cellulose surface. The polyvinyl alcohol (PVA) solution was impregnated into delignified wood, resulting in the formation of a cross-linked structure through multiple freeze–thaw cycles. After eight cycles, the tensile strength in the longitudinal direction reached up to 25.68 MPa with a strain of ~463%. This excellent mechanical strength is superior to that of most wood-based elastomers reported to date. The SWE can also perform complex deformations such as winding and knotting, and SWE soaked in salt solution exhibits excellent sensing characteristics and can be used to detect human finger bending. Stretchable wood-based elastomers with high mechanical strength and toughness have potential future applications in biomedicine, flexible electronics, and other fields. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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18 pages, 4009 KiB

Open AccessArticle

The Effect of Wet and Dry Cycles on the Strength and the Surface Characteristics of Coromandel Lacquer Coatings

by Wenjia Liu, Ling Zhu, Anca Maria Varodi, Xinyou Liu and Jiufang Lv

Forests 2024, 15(5), 770; https://doi.org/10.3390/f15050770 - 27 Apr 2024

Viewed by 644

Abstract

Research on the degradation mechanism of coating materials is crucial for the preservation of cultural heritage. The purpose of this study was to evaluate the protective effect of Coromandel coatings on wooden substrates by analyzing their dimensions, weight, adhesion strength, hydrophobicity, and glossiness. The results indicate that after five cycles, the radial moisture expansion rate of the wood specimen is 0.332%, while that of the lacquer specimen is 0.079%, representing 23.8% of the radial moisture expansion rate of untreated wood specimens. This performance is superior to that of the ash and pigment specimens. Across different experimental conditions, the change in the mass of the Coromandel specimens aligns with the trend in their dimensional changes, indicating that moisture absorption and desorption are the primary reasons for dimensional changes. The influence of temperature on mass and dimensional stability is significant only in terms of dry shrinkage rate. After wet and dry cycles at 40 °C, the adhesion strength of the Coromandel specimens decreases the most, with the ash specimens decreasing by 7.2%, the lacquer specimens by 3.2%, and the pigment specimens by 4.5%. Following wet and dry cycles at three different temperatures, the contact angle of the lacquer layers changes by less than 5%, with their contact angle values exceeding 120°. These data indicate that among the Coromandel coatings, the lacquer layer provides the best protection for the wooden substrate, while the ash coating is the most fragile. The degradation rate of the Coromandel specimens increases with rising temperatures. These findings emphasize the critical roles of humidity and temperature in protecting wooden coatings and aim to provide theoretical insights and practical significance for the preservation of wooden artifacts and the assessment of coating performance. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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17 pages, 5617 KiB

Open AccessArticle

A Novel Bamboo–Wood Composite Utilizing High-Utilization, Easy-to-Manufacture Bamboo Units: Optimization of Mechanical Properties and Bonding Performance

by Yifan Ma, Yu Luan, Lin Chen, Bin Huang, Xun Luo, Hu Miao and Changhua Fang

Forests 2024, 15(4), 716; https://doi.org/10.3390/f15040716 - 18 Apr 2024

Viewed by 859

Abstract

Bamboo–wood composites have found extensive applications in the container flooring, furniture, and construction industries. However, commonly utilized bamboo units such as four-side-planed rectangular bamboo strips and bamboo scrimber suffer from either low utilization rates or high adhesive content. The recently developed bamboo-flattening technology, which employs softening methods with saturated high-pressure steam, may improve the utilization rate and reduce the adhesive content, but its complex processes and high cost restrict its widespread application. This study introduces a novel bamboo–wood composite utilizing high-utilization, easy-to-manufacture bamboo units processed through a straightforward flattening-and-grooving method. However, the stress concentration introduced by the grooving treatment may affect the mechanical properties and stability of the bamboo–wood composites. In order to optimize the mechanical properties and bonding performance, response surface methodology based on a central composite rotatable design was used to map the effects of hot-pressing parameters (time, temperature, and pressure) on the mechanical properties. The bamboo-woodbamboo–wood composites prepared with optimized conditions of 1.18 min/mm pressing time, 1.47 MPa pressure, and a 150 °C temperature had a 121.51 MPa modulus of rupture and an 11.85 GPa modulus of elasticity, which exhibited an error of only ~5% between the experimental and model predictions. Finite element analysis revealed that, in comparison to homogeneous flat bamboo composites, grooved bamboo composites exhibited distinct tensile ductility and toughness due to discontinuous stress fields and alternating rigid–soft layers, which alter the stress transmission and energy dissipation mechanisms. Additionally, grooving treatment not only effectively improved the surface wettability of the bamboo plants, thus enhancing the permeability of the adhesive, but also facilitated adhesive penetration into parenchymal cells and fibers. This led to the formation of a more robust glue–nail structure and chemical bonding. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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15 pages, 4872 KiB

Open AccessArticle

Effect of High-Intensity Microwave Treatment on Structural and Chemical Characteristics of Chinese Fir

by Xiaomei Liao, Xuan Fang, Xin Gao, Songlin Yi and Yongdong Zhou

Forests 2024, 15(3), 516; https://doi.org/10.3390/f15030516 - 11 Mar 2024

Viewed by 1157

Abstract

High-intensity microwave (HIMW) treatment is a time-saving and environmentally friendly method widely applied in the wood processing industry. It enhances wood permeability, making it suitable for drying and impregnation modification. This study aimed to investigate the effects of HIMW on macroscopic and microscopic cracks, tracheid cell wall damage, and the chemical structure of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] wood. Through the use of a camera, optical microscope, scanning electron microscope, transmission electron microscope, Fourier-transform infrared spectroscopy, and X-ray diffraction, the morphology of cracks, cell wall damage, the chemical composition of the cell wall, and the crystalline structure of cellulose treated with HIMW were examined and analyzed. The results revealed that the initial moisture content (MC) and microwave energy density (MWED) significantly influenced the crack characteristics and cell wall structure and slightly influenced the chemical composition and crystalline structure of cellulose of the Chinese fir cell wall. HIMW treatment can produce different characteristics of wood cracks. The size and number of cracks were significantly increased with the increase in MWED, and more cracks were found in low MC. Microcracks caused by HIMW treatment tended to initiate at the ray parenchyma, resulting in the stripping of ray cells along its radial direction. Meanwhile, the cracking of adjacent cell junctions, the rupturing of the pit margo and pit torus, and cell wall parts tearing along the direction of microfibers occurred as a result of the HIMW treatment. The most severe damage to the cell walls occurred at the interface of S1/S2, S1, and ML layers, and the cell walls were torn in the S2 layer. There were no significant changes in the FTIR spectra of the HIMW treatment samples. Hemicellulose degradation occurred first, which increased with the increase in MWED. The recrystallization of cellulose and the lignin content increased because of the change in the aromatic C=O groups. As MWED increased, both the crystallinity index (CI) and cellulose crystal width (D₂₀₀) of the samples that underwent HIMW treatment increased accordingly, and the number of low-MC samples was greater than that of the high-MC samples. The findings contribute to understanding the crack characteristics and damage mechanism induced by HIMW treatment on wood. This study provides valuable insights into regulating the effects of HIMW treatment and expanding its application in wood processing, such as wood drying and functionalized impregnation, according to the specific end-use requirements. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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14 pages, 4697 KiB

Open AccessArticle

The Influence of Treatment Methods on Bending Mechanical Properties of Bamboo Strips

by Shiyu Cao, Jiagui Ji, Haowei Yin and Xuehua Wang

Forests 2024, 15(3), 406; https://doi.org/10.3390/f15030406 - 21 Feb 2024

Viewed by 993

Abstract

This study aimed to obtain a comprehensive understanding on bamboo as a curve-member manufacturing material by comparative analysis of how different treatment methods on bending properties improve the effect on bamboo strips. In order to achieve this purpose, bamboo strips were subjected to water boiling, 15% NaOH, and 25% NH₃ impregnation; the impact of physical, mechanical and chemical properties were explored. The results revealed that: (1) Water boiling significantly affected crystallinity, cellulose, and lignin content, with a treatment duration of 10 h showing the most favorable results for flexibility and plasticity, greatly improving bending performance. (2) An amount of 15% NaOH treatment significantly increased bending MOE and plastic displacement by 73% and 122.7%. However, it led to a noticeable decrease in bending strength (MOR). A treatment above 8 h could cause irreversible damage to bamboo strips. (3) The improvement of 25% NH₃ on bamboo bending ability was lower than water boiling. The effects of chemical composition were obvious in the initial five days and changed little after five days. Generally, water boiling for over 10 h is suitable for applications with significant bending requirements. While for maintaining bamboo color, original strength, and bending performance, 25% NH₃ for five days was recommended, and 15% NaOH was not advised for improving bamboo bending performance and its applications. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Wood- and Bamboo-Based Materials)

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