Delamination in Wood, Wood Products and Wood-Based Composites

ISBN-13: 9789048195497 / Angielski / Twarda / 2010 / 401 str.

Voichita Bucur

Opis

In the last quarter century, delamination has come to mean more than just a failure in adhesion between layers of bonded composite plies that might affect their load-bearing capacity. Ever-increasing computer power has meant that we can now detect and analyze delamination between, for example, cell walls in solid wood. This fast-moving and critically important field of study is covered in a book that provides everyone from manufacturers to research scientists the state of the art in wood delamination studies. Divided into three sections, the book first details the general aspects of the subject, from basic information including terminology, to the theoretical basis for the evaluation of delamination. A settled terminology in this subject area is a first key goal of the book, as the terms which describe delamination in wood and wood-based composites are numerous and often confusing. The second section examines different and highly specialized methods for delamination detection such as confocal laser scanning microscopy, light microscopy, scanning electron microscopy and ultrasonics. Ways in which NDE (non-destructive evaluation) can be employed to detect and locate defects are also covered. The book's final section focuses on the practical aspects of this defect in a wide range of wood products covering the spectrum from trees, logs, laminated panels and glued laminated timbers to parquet floors. Intended as a primary reference, this book covers everything from the microscopic, anatomical level of delamination within solid wood sections to an examination of the interface of wood and its surface coatings. It provides readers with the perspective of industry as well as laboratory and is thus a highly practical sourcebook for wood engineers working in manufacturing as well as a comprehensively referenced text for materials scientists wrestling with the theory underlying the subject.

Spis treści

PART 1: GENERAL ASPECTS. 1. Introduction. 1.1 Solid wood. 1.2 Wood-based composites. 1.3 Summary;V. Bucur.- 2. Terms for delamination in wood science and technology;2.1 General terms. 2.2 Terms for delamination in solid wood. 2.3 Terms for delamination in cell wall. 2.4 Terms for delamination in laminated wood products. 2.5 Terms for delamination in wood-based fiber and particle panels. 2.6 General classification terms. 2.7 Summary; V. Bucur.- 3. Delamination evaluation - a vibration-based approach. 3.1 Introduction. 3.2 Delamination evaluations with ultrasonics. 3.3 Model-based methods using low frequency vibrations. 3.3.1 Linear behavior. 3.3.2 Nonlinear behavior. 3.4 Summary. Appendix: Dynamics of delaminated beams; V. Bucur.- 4. Crack initiation and growth of delamination in wood and wood-based composites: a Fracture Mechanics approach. 4.1 Introduction. 4.1.1 Linear elastic Fracture Mechanics. 4.1.2 Nonlinear Fracture Mechanics. 4.2 Structural aspects in wood. 4.2.1 Cell wall level – micro scale. 4.2.2 Growth ring level – meso scale. 4.2.3 Clear wood – macro scale. 4.2.4 Structural wood products – massive scale. 4.3 Structural aspects in wood-based composites. 4.3.1 Laminated wood-based composites. 4.3.2 Fibrous based composites. 4.4 Delamination and ecological relevance. 4.6 Summary; V. Bucur.- 5. A theoretical model of collapse recovery. 5.1 Introduction. 5.2 Repeating cell unit model with cyclical constrains. 5.2.1 Cell wall layer properties. 5.2.2 Circular based cell model. 5.2.3 Square based model. 5.3 Summary; P. Blakemore.- PART 2: METHODOLOGY FOR DELAMINATION DETECTION AND FACTORS INDUCING AND AFFECTING DELAMINATION. 6. Delamination of wood at the microscopic scale: current knowledge and methods. 6.1 Anatomical features of wood delamination. 6.1.1 Weathering and decay. 6.1.2 Internal and intra – ring checking. 6.1.3 Resin pockets. 6.1.4 Shelling. 6.1.5 Reaction wood. 6.1.6 Induced delamination. 6.2 Ultrastructural features of cell wall delamination. 6.2.1 Ultrastructure of wood cell walls. 6.2.2 Location of cell wall delamination. 6.2.3 Mechanism of delamination. 6.2.4 Influence of microfibril angle. 6.2.5 Influence of delignification and pulp refining. 6.2.6 Influence of species. 6.2.7 Influence of moisture content. 6.2.8 Influence of temperature. 6.3 Microscopic methods for evaluation of delamination in wood. 6.3.1 Light microscopy. 6.3.2 Confocal microscopy. 6.3.3 Electron microscopy. 6.4 Conclusion. 6.5 Summary; L. Donaldson.-7. Probing the wood coating interface at high resolution. 7.1 Introduction. 7.2 Confocal laser scanning microscopy. 7.2.1 High resolution CLSM examination of wood-coating interface: coating penetration into cell-wall micro-cracks. 7.2.2 Combined light microscopy, confocal laser scanning microscopy and scanning electron microscopy reveals a complex wood-coating interaction. 7.3 Wood-coating interface examined by field emission scanning electron microscope in combination with backscattered electron imaging. 7.4 Conclusion. 7.5 Summary; A.P. Singh, B.S.W. Dawson.- 8. Delamination in timber induced by microwave energy. 8.1 Introduction. 8.2 Dielectric properties of wood. 8.3 The mechanism of wood delamination induced by microwaves. 8.4 Solid wood delamination in various microwave applications. 8.4.1 Impregnation. 8.4.2 Drying. 8.4.3 Bending. 8.5 Controlling the microwave delamination zone in timber. 8.6 Conclusion. 8.7 Summary; G. Daian.- 9. Delamination in wood and wood products induced by weathering. 9.1. Background. 9.2. Delamination in solid wood. 9.2.1 Methods of measurements. 9.2.2 Macroscopic aspects. 9.2.3 Microscopic aspects. 9.3. Delamination in wood products and wood panels. 9.3.1 Outdoor exposure. 3.2 Artificial exposure. 9.4 Summary; V. Bucur.- 10. Delamination in timber induced by drying. 10.1 Introduction. 10.2 Influence of temperature, relative humidity and rate of air circulation on drying. 10.2.1 Temperature. 10.2.2 Relative humidity. 10.2.3 Air circulation rate. 10.3 Wood drying. 10.3.1 Air drying. 10.3.4 Kiln drying. 10.4 Kiln drying schedules. 10.5 Drying defects. 10.6 Prediction of drying stress and strain using mathematical models. 10.6.1 Hardwood. 10.6.2 Softwood. 10.7 Conclusion. 10.8 Summary; N. Haque.- PART 3: DELAMINATION IN DIFFERENT PRODUCTS. 11. Industry prospective of delamination in wood and wood products. 11.1 Introduction. 11.2 The unique structure of wood. 11.3 The raw materials: trees and stems or logs. 11.4 The manufacturing process. 11.4.1 Solid wood products. 11.4.2 Engineered wood products. 11.5 Products failure and products durability. 11.5.1 Products failure. 11.5.2 Product durability. 11.6 Summary; C.L. Huang.- 12. Internal checking during Eucalypt processing. 12.1 Introduction. 12.2 Why is drying slow and collapse high in eucalypts. 12.3 Causes of surface and internal checking in eucalypts. 12.4 Eucalypts species prone to collapse. 12.5 Collapse recovery and check closure. 12.6 Dimensional analysis and predictions from heat-transfer theory. 12.7 Effect of reconditioning on internal checking. 12.8 Summary; P. Blakemore.- 13. Acoustic tomography for tension wood detection in eucalypts. 13.1 Introduction. 13.2 Acoustic tomography. 13.2.1 Materials. 13.2.2 Methods. 13.2.2.1 Ultrasonic velocity measurements. 13.2.2.2 Stress wave velocity measurements. 13.3 Tension wood detection with ultrasonic velocity method. 13.4 Acoustic imaging with stress wave technique. 13.4.1 Radial stress waves velocities. 13.4.2 Tangential stress waves velocities. 13.5 Conclusion. 13.6 Summary; V. Bucur.- 14. Modeling of hygroscopic warping of laminated wood panels. 14.1 Introduction. 14.1.1 Background. 14.1.2 Limitations. 14.2 Theoretical background. 14.2.1 Modeling moisture movement in wood. 14.2.2 Modeling moisture induced stress and deformations. 14.3 Experimental methods. 14.4 Model validation. 14.4.1 Material properties. 14.4.2 Finite element model. 14.5 Results and discussion. 14.6 Conclusion. 14.7 Summary; T. Gereke et al.- 15. Acoustic emission activity induced by delamination and fracture of wood. 15.1 Introduction. 15.2 Parameters of the acoustic emission signals. 15.3 Parameter-based acoustic technique for wood. 15.3.1 Species effect. 15.3.2 Grain angle effect. 15.3.3 Annual ring structure. 15.3.4 Tension wood. 15.3.5 Moisture content. 15.3.6 Old, reused wood. 15.4 Some aspects relayed to the energy of acoustic signals. 15.5 Summary; V. Bucur.- 16. Delamination detection in wood-based composite panels products using ultrasonics. 16.1 Introduction. 16.2 Basic aspects. 16.2.1 Wave propagation path. 16.2.2 Linear ultrasonic inspection techniques. 16.2.2.1 Contact techniques. 16.2.2.1.1 Pulse echo technique. 16.2.2.1.2 Through transmission technique. 16.2.2.2 Non-contact techniques. 16.2.3 Ultrasonic transducers and scanning procedures. 16.2.3.1 Contact transducers. 16.2.3.2 Non contact transducers. 16.2.3.3 Scanning procedures. 16.2.4 Nonlinear ultrasonic inspection techniques. 16.3 Delamination detection in panel products. 16.3.1 Through transmission technique. 16.3.1.1 Technique with transducers in contact. 16.3.1.2 Non contact ultrasonic transducers. 16.3.2 Plate wave technique. 16.3.2.1 Technique with transducers in contact. 16.3.2.2 Non contact ultrasonic transducers. 16.3.3 Industrial applications of non contact technique. 16.4 Summary; V. Bucur, S. Kasemi-Najafi.- 17. Evaluation of in-service glulam beams by an acoustic technique. 17.1 Introduction. 17.2 Crack types. 17.2.1 Cracks between lamellae. 17.2.2 Cracks inside the laminated material. 17.3 Crack depth determination by acoustical methods. 17.3.1 Lamellae strength prediction. 17.3.2 Detection of other internal defects in glulam. 17.3.3 Shear strength between the lamellae. 17.4 Summary; F. Divos.- 18. Moisture induced stresses and deformations in parquet floors. 18.1 Introduction. 18.2 Material and method. 18.2.1 Tests on basic material. 18.2.2 Tests on parquet planks. 18.2.3 Analytical model A: calibration model. 18.2.4 Analytical model B: distortional effects. 18.2.5 Analytical model C: gap opening. 18.3 Results. 18.3.1 Model A: Calibration and comparison to test series 2. 18.3.2 Model B: Cupping of the parquet. 18.3.3 Model C: Stresses in the glue line and gap opening. 18.4 Conclusion. 18.5 Summary; S. Blumer et al.- 19. Nondestructive glue line assessment in timber laminates with an air-coupled ultrasonic technique. 19.1 Introduction. 19.2 Material and methods. 19.2.1 Sample preparation. 19.3 Theoretical considerations. 19.4 Experimental setup. 19.5 Results and discussion. 19.5.1 Imaging of glue presence and repeatability of measurements. 19.5.2 Influence of natural variability and anisotropy of wood. 19.6 Conclusion. 19.7 Summary; M.S.J. Sanabria et al.- 20. From present researches to future developments; V. Bucur.-21. Subject Index; V. Bucur.-