The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

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378 Appendices B-6 Oven Dry Weight of Veneers of Varying Thicknesses by Species 1 Ounces Per Square Foot Veneer Specific % Air Dry Moisture Veneer Thickness in Inches Species Gravity2 Content 1 ⁄16 1 ⁄8 3 ⁄16 Birch, Yellow 0.63 9.6 3.28 6.56 9.84 13.12 Cedar, Spanish 0.37 7.3 1.92 3.85 5.77 7.70 Cedar, Red 0.31 1.83 3.67 5.49 7.34 Fir, Douglas 0.51 6.2 2.65 5.30 7.96 10.6 Mahogany, African 0.46 8.0 2.39 4.78 7.17 9.57 Mahogany, Central American 0.49 7.9 2.55 5.10 7.66 10.20 Spruce, Sitka 0.38 8.9 1.98 3.96 5.94 7.94 1 Extracted from Michelon and Devereaux, p. 163 2 Based on oven dry weight and air dry volume. B-7 Approximate Weights of Finished Western Red Cedar Laminates 1 Number of Average Pounds 1 ⁄8" Thick Layers Per Square Foot 4 (totaling 1 ⁄2") 1.30 5 (totaling 5 ⁄8") 1.65 6 (totaling 3 ⁄4") 2.00 7 (totaling 7 ⁄8") 2.35 8 (totaling 1") 2.70 9 (totaling 1") 3.00 1 Includes weight of WEST SYSTEM epoxy used in bonding and coating all surfaces. All samples were weighed at the <strong>Gougeon</strong> <strong>Brothers</strong>, Inc. test facility. 1 ⁄4
Fatigue Aspects of Epoxies and Wood/Epoxy Composites In materials science, fatigue is the name for the process of weakening materials and structures by subjecting them to repeated loads. This paper addresses the cyclic fatigue-related degradation of epoxy composite materials and serves as a guide to a better understanding of this very complex composite material failure mode. All materials suffer damage from dynamic loads–some more so than others. This damage usually cannot be seen or in any other way measured until failure is imminent. Understanding this fatigue degradation process is difficult even with homogeneous materials, such as metals. For composites, it is the mix of different materials, directional properties, and load paths, each with its own unique response to fatigue loads, that presents the greatest challenge in characterizing fatigue performance. Introduction Since the early 1980s, <strong>Gougeon</strong> <strong>Brothers</strong> has conducted an extensive series of fatigue research programs. <strong>The</strong>se were originally designed to support our efforts to build wind turbine blades that could withstand 400 million fatigue cycles over a thirty-year life span. In addition, these testing programs had to provide a basis for developing quality control procedures that could assure 100% success with a given manufacturing process. Optimizing the blade design for weight, performance, and reliability became paramount. <strong>The</strong> success of this program has been demonstrated with the manufacture of more than 4,200 rotor blades, not one of which has failed under designed operating conditions. <strong>The</strong> data presented in this paper relate to the two materials most used in <strong>Gougeon</strong> wind turbine blade and boat manufacturing: epoxy resins and Douglas fir veneer in the form of wood/epoxy composites. <strong>The</strong> purpose of presenting this data is not to attempt a definitive materials characterization, but to portray some important issues of wood composite material fatigue. Glass fiber reinforcing materials were also used in our wind blade and boat manufacturing efforts. Because this material plays a more minor role and its performance characteristics are well reported in other papers, we do not cover its performance characteristics in depth with this paper. APPENDIX C Before proceeding with a discussion of the wood-epoxy fatigue data, some key elements associated with classical fatigue testing need to be explained. First of all, when operating in fatigue mode, test machines apply a force to each material specimen that increases and decreases in a regular pattern, a pattern that corresponds to a mathematical sine-wave function. In other words, the repeating force pattern has smoothly rounded peaks and valleys. One cycle of load consists of one swing from the valley up to the summit and back down to the valley again. Note: <strong>The</strong> test force is supposed to reach the same prescribed maximum and minimum value on every load cycle, regardless of the condition of the specimen (until it breaks). Test engineers typically present the results of a particular fatigue test in terms of the cycles to failure for a specified peak load or peak stress. This is the basis of the S-N curve, a graphical display where “S” stands for the peak stress and “N” stands for the number of cycles a given specimen withstood before it broke. Sometimes the peak stress is expressed as a percent of the ultimate strength of a material, as measured in a previous static strength test (see Figure C-1). Another important term is Stress Ratio, which is sometimes designated as R Value. It is defined as the ratio of the load minimum to the load maximum for a typical fatigue cycle and is a parameter which is always specified (and held constant) in any classical fatigue test series. If the R value was set to 0.1 for a test series, it means that the load in the valley was always one-tenth of the load at the peak for all cycles. <strong>The</strong> terms “Stress Ratio” and “R Value” are interchangeable. It takes both the peak stress and the stress ratio to adequately characterize a classical fatigue test. <strong>The</strong> Fatigue Question <strong>The</strong> problem with static test data is that it only explains how a material behaves under a single application of load large enough to cause failure. Boats rarely fail under this kind of static loading. Most failures occur only after many thousands or millions of much smaller loads, which very slowly and systematically unravel a material. All materials respond differently to fatigue stresses and are characterized by a fatigue curve as
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The Gougeo
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Gougeon Br
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iv Table of Content Getting Started
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vi Table of Content Chapter 17 Mold
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viii Table of Content Later Product
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x Preface The brie
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xii Table of Content
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2 Introduction With the help of fri
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4 Introduction
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Modern Wood/Epoxy Composite Boatbui
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Chapter 2 - Modern Wood/Epoxy Compo
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Wood as a Structural Material CHAPT
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Chapter 3 - Wood as a Structural Ma
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WEST SYSTEM ® Products This chapte
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Chapter 4 - WEST SYSTEM ® Products
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Hull Construction Techniques— An
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Chapter 5 - Hull Construction Techn
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Getting Started Chapter 6 Before Yo
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46 Getting Started Finally, should
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48 Getting Started Designers’ fee
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50 Getting Started
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52 Getting Started Material Price/b
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54 Getting Started between layers o
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56 Getting Started mast; sails and
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58 Getting Started
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60 Getting Started and it is import
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62 Getting Started necessity. We al
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64 Getting Started Grit refers to t
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66 Getting Started An efficient flo
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68 Getting Started Ridge Pole Frame
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70 Getting Started
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72 Getting Started unimproved lumbe
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74 Getting Started If it is not yet
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76 Getting Started chapters, we adv
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78 Getting Started
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80 Getting Started The</str
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82 Getting Started cures quickly to
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84 Getting Started Evap. Rate LEL2
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86 Getting Started 4. Use wet, rath
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88 Getting Started
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Laminating and Bonding Techniques <
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Chapter 11 - Laminating and Bonding
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Scarfing Scarfing remains an essent
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Chapter 12 - Scarfing 109 and used
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Chapter 12 - Scarfing 111 Productio
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Chapter 12 - Scarfing 113 Figure 12
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Chapter 12 - Scarfing 115 Figure 12
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Chapter 12 - Scarfing 117 bevels on
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Synthetic Fibers and WEST SYSTEM ®
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Chapter 13 - Synthetic Fibers and W
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Hardware Bonding As stated earlier
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Chapter 14 - Hardware Bonding 135 A
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Chapter 14 - Hardware Bonding 137 F
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Chapter 14 - Hardware Bonding 141 F
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Chapter 14 - Hardware Bonding 143 W
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Chapter 14 - Hardware Bonding 147 W
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Chapter 14 - Hardware Bonding 149 K
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Coating and Finishing Broadly, the
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Chapter 15 - Coating and Finishing
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First Production Steps Chapter 16 L
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166 First Production Steps Hull Lin
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168 First Production Steps Figure 1
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170 First Production Steps 1" X 4"
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172 First Production Steps After ch
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174 First Production Steps did the
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176 First Production Steps stem or
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180 First Production Steps case you
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182 First Production Steps curve th
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184 First Production Steps Mark the
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186 First Production Steps
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188 First Production Steps will be
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190 First Production Steps Notches
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192 First Production Steps image an
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194 First Production Steps probably
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202 First Production Steps Setting
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204 First Production Steps To detec
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206 First Production Steps Beveling
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208 First Production Steps Section
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210 First Production Steps Stem lam
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216 First Production Steps Keel Fai
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Building a Mold or Plug A mold is a
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Chapter 20 - Building a Mold or Plu
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Laminating Veneer Over a Mold or Pl
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Chapter 21 - Laminating Veneer Over
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Stringer-Frame Construction While s
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Strip Plank Laminated Veneer and St
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Hard Chine Plywood Construction A s
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Chapter 24 - Hard Chine Plywood Con
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Compounded Plywood Construction Mos
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Later Production Steps Chapter 26 I
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318 Later Production Steps Figure 2
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320 Later Production Steps Figure 2
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322 Later Production Steps Material
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324 Later Production Steps Bulkhead
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326 Later Production Steps Teak ven
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The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

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