Failure Analysis of Wood and Wood-Based Products

Dr. Dirk Lukowsky started his career as a finish carpenter, eventually qualifying as a master cabinetmaker. After ten years spent learning his craft, he studied wood science and technology at the University of Hamburg and earned his Ph.D. with a thesis on the protection of wood with melamine resins. Since 1999, he has worked at the Fraunhofer Institute for Wood Research (WKI) in Brunswick, where he specializes in failure analysis and wood protection.

• 1 Preface 2 Principles of failure analysis 2.1 Avoiding mistakes 2.2 Sampling 2.3 Differential findings 2.3.1 Patterns 2.3.2 Time of appearance 2.3.3 Organizational hints 2.3.4 Comparison with common materials 3 Failure characteristics 3.1 Cracks 3.1.1 Cracks in MDF edges 3.1.2 Cracks in solid wood 3.2 Delamination 3.2.1 Adhesives 3.2.2 Coatings 3.3 Surface defects 3.3.1 Discoloration 3.3.2 Maceration 3.4 Deformation 4 Causes for failures 4.1 Solid wood4.1.1 Fiber deviations 4.1.2 Slip planes 4.1.3 Extractives 4.2 Wood composites 4.2.1 Delamination of coatings 4.2.2 Large particles/holes in the surface layer 4.2.3 Veneer cracks 4.3 Bonding 4.3.1 Glue thickness/pressure 4.3.2 Unpressed glue beads 4.3.3 Adhesive bleeding 4.4 Coating 4.4.1 Coating thickness 4.4.2 Microfoam 4.4.3 Surface preparation 4.4.4 Elasticity/ductility 4.5 Chemical influences 4.5.1 Coatings and adhesives 4.5.2 Reactions with iron 4.6 Geometrical aspects 4.6.1 Stress concentrations 4.6.2 Parallel veneers in plywood 4.6.3 Edge loss 4.7 Conditions of use 4.7.1 Moisture 4.7.2 UV radiation 4.7.3 Temperature 4.7.4 Mechanical stresses 5 Methods 5.1 Sampling 5.2 Documentation 5.2.1 Photography5.2.2 Scanning 5.2.3 Imprints 5.2.4 Frottage 5.2.5 Fluorescence 5.2.6 Accuracy of measurements 5.2.7 Estimation of distributions and amounts 5.3 Sanding from above 5.4 Patterns of features 5.4.1 Large scale patterns 31 drawings show possible patterns of defects and their interpretation. I have never seen anything similar in a publication. 5.4.2 Distribution in buildings 5.5 Chronology of patterns5.5.1 Discolorations and layer analysis5.5.2 Fungi/Insects 5.5.3 Honey bread effect 5.5.4 Thickness of materials 5.6 Reproduction of production- and use conditions 5.7 Wood moisture content 5.7.1 Electronic measurement5.7.2 Oven drying 5.7.3 Geometrical moisture estimation 5.7.4 Further hints for moisture conditions 5.8 Physical methods .5.8.1 Bonding tests 5.8.2 Mechanical coating testing 5.8.3 Water uptake/wetting/capillarity 5.8.4 Density 5.8.5 Thermal flow thermography5.8.6 Estimation of stresses 5.9 Microscopy 5.9.1 USB-Microscopes 5.9.2 Sample preparation 5.9.3 Lighting methods 5.9.4 Microscopic features in cross sections 5.9.5 Coating thickness and coating buildup 5.9.6 Analysis of starch grains 5.10 Chemical methods 5.10.1 Staining 5.10.2 Instrumental techniquesReferences Index