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97 pages, 144318 KiB

Open AccessArticle

A Review on Acoustics of Wood as a Tool for Quality Assessment

by Voichita Bucur

Forests 2023, 14(8), 1545; https://doi.org/10.3390/f14081545 - 28 Jul 2023

Cited by 7 | Viewed by 2917

Abstract

Acoustics is a field with significant application in wood science and technology for the classification and grading, through non-destructive tests, of a large variety of products from standing trees to building structural elements and musical instruments. In this review article the following aspects [...] Read more.

Acoustics is a field with significant application in wood science and technology for the classification and grading, through non-destructive tests, of a large variety of products from standing trees to building structural elements and musical instruments. In this review article the following aspects are treated: (1) The theoretical background related to acoustical characterization of wood as an orthotropic material. We refer to the wave propagation in anisotropic media, to the wood anatomic structure and propagation phenomena, to the velocity of ultrasonic waves and the elastic constants of an orthotropic solid. The acoustic methods for the determination of the elastic constants of wood range from the low frequency domain to the ultrasonic domain using direct contact techniques or ultrasonic spectroscopy. (2) The acoustic and ultrasonic methods for quality assessment of trees, logs, lumber and structural timber products. Scattering-based techniques and ultrasonic tomography are used for quality assessment of standing trees and green logs. The methods are based on scanning stress waves using dry-point-contact ultrasound or air-coupled ultrasound and are discussed for quality assessment of structural composite timber products and for delamination detection in wood-based composite boards. (3) The high-power ultrasound as a field with important potential for industrial applications such as wood drying and other applications. (4) The methods for the characterization of acoustical properties of the wood species used for musical instrument manufacturing, wood anisotropy, the quality of wood for musical instruments and the factors of influence related to the environmental conditions, the natural aging of wood and the effects of long-term loading by static or dynamic regimes on wood properties. Today, the acoustics of wood is a branch of wood science with huge applications in industry. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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Review

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44 pages, 109167 KiB

Open AccessReview

Hardwoods: Anatomy and Functionality of Their Elements—A Short Review

by Luis G. Esteban, Paloma de Palacios, Peter Gasson, Alberto García-Iruela, Francisco García-Fernández and Lydia García-Esteban

Forests 2024, 15(7), 1162; https://doi.org/10.3390/f15071162 - 4 Jul 2024

Cited by 1 | Viewed by 2027

Abstract

Hardwoods are complex heterogeneous and orthotropic structures that have evolved to the present day, adapting to successive climate episodes to prosper on Earth. Attributing a specific functionality to individual hardwood elements is difficult because of their interconnection in this heterogeneous three-dimensional network. However, [...] Read more.

Hardwoods are complex heterogeneous and orthotropic structures that have evolved to the present day, adapting to successive climate episodes to prosper on Earth. Attributing a specific functionality to individual hardwood elements is difficult because of their interconnection in this heterogeneous three-dimensional network. However, tree physiology research is helping to enhance knowledge in this field. This work is a short review of the possible functionalities of hardwood elements, in some cases supported by experimentation and in others by comparative anatomy. It is intended for students or researchers starting out in the world of hardwood anatomy to aid their understanding of the functionality of hardwood elements. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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61 pages, 12964 KiB

Open AccessReview

Mechanical Properties of Wood: A Review

by Francisco Arriaga, Xiping Wang, Guillermo Íñiguez-González, Daniel F. Llana, Miguel Esteban and Peter Niemz

Forests 2023, 14(6), 1202; https://doi.org/10.3390/f14061202 - 9 Jun 2023

Cited by 22 | Viewed by 14834

Abstract

The use of wood in construction requires knowledge of the mechanical properties and the particularities that wood presents in comparison with other materials used for structural purposes such as steel, concrete, brick, or stone. The introduction mentions the environmental advantages that justify the [...] Read more.

The use of wood in construction requires knowledge of the mechanical properties and the particularities that wood presents in comparison with other materials used for structural purposes such as steel, concrete, brick, or stone. The introduction mentions the environmental advantages that justify the use of wood today. The orthotropy of wood is one of the differentiating characteristics that must be taken into account when studying its behaviour. The determination of the properties of wood is then addressed from a historical perspective and the differentiation is made between the properties of small clear wood (defect-free timber) and structural timber. The timber grading systems (visual and mechanical grading) and the non-destructive techniques that currently prevail are explained. Finally, the factors that influence the mechanical properties, such as duration of the load, moisture content, quality, temperature, and the effect of size are explained. The objective of this work is to provide an overview of the current knowledge on the mechanical properties of wood, based mainly on published articles and European and North American standards, including historical references to the beginnings and current trends in this field. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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36 pages, 28070 KiB

Open AccessReview

The Macroscopic Structure of Wood

by Flavio Ruffinatto, Francesco Negro and Alan Crivellaro

Forests 2023, 14(3), 644; https://doi.org/10.3390/f14030644 - 21 Mar 2023

Cited by 6 | Viewed by 7971

Abstract

Understanding the macroscopic structure of wood and its formation is essential to identifying wood and evaluating its properties and quality. Depending on genetic background, environmental conditions, and tree developmental stage, the macroscopic structure of wood can vary greatly and produce specific macroscopic signatures. [...] Read more.

Understanding the macroscopic structure of wood and its formation is essential to identifying wood and evaluating its properties and quality. Depending on genetic background, environmental conditions, and tree developmental stage, the macroscopic structure of wood can vary greatly and produce specific macroscopic signatures. Here, a comprehensive outline of the wood’s macroscopic structure and the features that can be used to identify wood by macroscopic examination is presented. The planes of observations are first depicted, and the fundamental differences between softwoods and hardwoods are outlined. Then, all the different cell characteristics, arrangements, and distributions that can be macroscopically observed are illustrated with their influence on wood figure and texture and non-anatomical features. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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67 pages, 137730 KiB

Open AccessReview

Softwood Anatomy: A Review

by Luis G. Esteban, Paloma de Palacios, Immo Heinz, Peter Gasson, Alberto García-Iruela and Francisco García-Fernández

Forests 2023, 14(2), 323; https://doi.org/10.3390/f14020323 - 6 Feb 2023

Cited by 12 | Viewed by 5083

Abstract

Although conifers have very homogeneous wood anatomical structure, some of their features allow differentiation of genera or groups of genera. Softwood anatomy is reviewed and the authors have added contributions, grouping features in five blocks (axial tracheids, axial parenchyma, rays, resin canals and [...] Read more.

Although conifers have very homogeneous wood anatomical structure, some of their features allow differentiation of genera or groups of genera. Softwood anatomy is reviewed and the authors have added contributions, grouping features in five blocks (axial tracheids, axial parenchyma, rays, resin canals and mineral inclusions), with special attention to their diagnostic value at the family, genus or species levels. The discussion addresses, in axial tracheids: growth rings, intercellular spaces, pit arrangement, presence of scalloped tori, torus extensions, notches, warty layer, organic deposits, helical and callitroid thickenings, bars of Sanio and trabeculae; in axial parenchyma: presence or absence, arrangement and type of transverse end walls; in rays: composition, type of horizontal and end walls and cross-field pitting; in resin canals: epithelium and the presence of normal or traumatic resin canals; and in mineral inclusions: presence or absence. Wood structure is characterised at the family level, discussing the main elements that can be used for diagnosis at the genus level or in groups of genera. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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34 pages, 7584 KiB

Open AccessReview

Biological Deterioration and Natural Durability of Wood in Europe

by Juan A. Martín and Rosana López

Forests 2023, 14(2), 283; https://doi.org/10.3390/f14020283 - 1 Feb 2023

Cited by 20 | Viewed by 9333

Abstract

In recent years, the use of wood has gained social interest, leading to a global increase in its demand. Yet, this demand is often covered by the production of woods of low natural durability against biological deterioration. The main biological agents with the [...] Read more.

In recent years, the use of wood has gained social interest, leading to a global increase in its demand. Yet, this demand is often covered by the production of woods of low natural durability against biological deterioration. The main biological agents with the potential to attack the structural integrity of wood are wood-decay fungi, saproxylic beetles, termites, and marine molluscs and crustaceans. In most circumstances, fungi are the main wood-deteriorating agents. To attack the cell wall, wood-decay fungi combine a complex enzymatic mechanism with non-enzymatic mechanisms based on low-molecular-weight compounds. In some cases, the larvae of saproxylic beetles can also digest cell wood components, causing serious deterioration to wooden structures. The impact of subterranean termites in Europe is concentrated in the Southern countries, causing important economic losses. However, alien invasive species of voracious subterranean termites are expanding their presence in Europe. Wooden elements in permanent contact with marine water can be readily deteriorated by mollusc and crustacean borers, for which current preservatives lack efficacy. The natural durability of wood is defined as the inherent resistance of wood to catastrophic action by wood-destroying organisms. Besides exposure to the climate, product design and use conditions, the natural durability of wood is key to the prediction of the service life of wooden products, which can be shortened due to the impact of global change. The major wood properties involved in natural durability are related to the composition of lignin in the cell wall, the anatomy of the xylem, nutrient availability, the amount and composition of heartwood extractives, and the presence of moisture-regulating components since wood moisture content influences the establishment of wood-degrading organisms. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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30 pages, 3691 KiB

Open AccessEditor’s ChoiceReview

Water in Wood: A Review of Current Understanding and Knowledge Gaps

by Emil Engelund Thybring, Maria Fredriksson, Samuel L. Zelinka and Samuel V. Glass

Forests 2022, 13(12), 2051; https://doi.org/10.3390/f13122051 - 2 Dec 2022

Cited by 44 | Viewed by 13081

Abstract

Wood-water interactions are central to the utilization of wood in our society since water affects many important characteristics of wood. This topic has been investigated for more than a century, but new knowledge continues to be generated as a result of improved experimental [...] Read more.

Wood-water interactions are central to the utilization of wood in our society since water affects many important characteristics of wood. This topic has been investigated for more than a century, but new knowledge continues to be generated as a result of improved experimental and computational methods. This review summarizes our current understanding of the fundamentals of water in wood and highlights significant knowledge gaps. Thus, the focus is not only on what is currently known but equally important, what is yet unknown. The review covers locations of water in wood; phase changes and equilibrium states of water in wood; thermodynamics of sorption; terminology including cell wall water (bound water), capillary water (free water), fiber saturation point, and maximum cell wall moisture content; shrinkage and swelling; sorption hysteresis; transport of water in wood; and kinetics of water vapor sorption in the cell wall. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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46 pages, 4818 KiB

Open AccessEditor’s ChoiceReview

Review of Wood Modification and Wood Functionalization Technologies

by Samuel L. Zelinka, Michael Altgen, Lukas Emmerich, Nathanael Guigo, Tobias Keplinger, Maija Kymäläinen, Emil E. Thybring and Lisbeth G. Thygesen

Forests 2022, 13(7), 1004; https://doi.org/10.3390/f13071004 - 26 Jun 2022

Cited by 71 | Viewed by 12776

Abstract

Wood modifications are becoming popular as a way to enhance the performance of wood, either to make it more durable, improve the performance of wood, or give it new functionality as a multifunctional or smart material. While wood modifications have been examined since [...] Read more.

Wood modifications are becoming popular as a way to enhance the performance of wood, either to make it more durable, improve the performance of wood, or give it new functionality as a multifunctional or smart material. While wood modifications have been examined since the early 1900s, the topic has become a dominant area of study in wood science over the past decade. This review summarizes recent advances and provides future perspective on a selection of wood modifications, i.e., the methods that are currently commercialized (acetylation, furfurylation, and thermal modification), a rediscovered ancient practice (charring), a family of polymerization modifications that have so far made it to the pilot scale, and examples of novel wood-based functional materials explored at laboratory scale. Full article

(This article belongs to the Special Issue Reviews on Structure and Physical and Mechanical Properties of Wood)

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