CHAPTER 11 Wood-Based Composite Materials Panel Products, Glued Laminated Timber, Structural Composite Lumber, and Wood–Nonwood Composites Nicole M. Stark, Research Chemical Engineer Zhiyong Cai, Supervisory Research Materials Engineer Because wood properties vary among species, between Contents trees of the same species, and between pieces from the Conventional Wood-Based Composite Panels 11–2 same tree, solid wood cannot match reconstituted wood Wood Elements 11–3 in the range of properties that can be controlled. Wood Adhesives 11–3 with localized defects (such as knots) can often be utilized effectively in wood-based composites. When wood with Additives 11–6 defects is reduced to wood elements, the influence of these Plywood 11–6 characteristics in the manufactured product is reduced. Oriented Strandboard 11–10 To reinforce sustainable harvesting efforts, wood derived Particleboard 11–11 from small-diameter timber, forest residues, or exotic and invasive species may also be used in wood-based Fiberboard 11–13 composites. Specialty Composite Materials 11–16 Wood-based composite materials can be made up of various Performance and Standards 11–17 wood elements, including fibers, particles, flakes, veneers, Glued Laminated Timber 11–18 or laminates. Properties of such materials can be changed Advantages 11–18 by combining, reorganizing, or stratifying these elements. Types of Glulam Combinations 11–19 When raw material selection is paired with properly selected processing variables, the end result can surpass nature’s best Standards and Specifications 11–19 effort. Manufacture 11–20 The basic element for composite wood products is the fiber, Structural Composite Lumber and Timber with larger particles composed of many fibers (Fig. 11–1). Products 11–21 Elements used in production of wood-based composites can Laminated Veneer Lumber 11–22 be made in a great variety of sizes and geometries and can Parallel Strand Lumber 11–22 be used alone or in combination. The choices are almost unlimited. The control of these characteristics—size and Laminated Strand Lumber and Oriented Strand geometry—provide the chief means by which composite Lumber 11–22 materials can be fabricated with predetermined properties. Advantages and Uses 11–22 Currently, the term composite is being used to describe Standards and Specifications 11–23 any wood material adhesively bonded together. This Wood–Nonwood Composite Materials 11–23 encompasses a range of products from fiberboard to Cement-Bonded Composite Materials 11–24 laminated beams and components. Table 11–1 shows a Ceramic-Bonded Composite Materials 11–26 logical basis for classifying wood composites proposed by Maloney (1986). For this chapter, these classifications Wood–Thermoplastic Composite Materials 11–26 were slightly modified from those in the original version to Cellulose Nanocomposites 11–28 reflect the latest product developments. Composites are used Literature Cited 11–28 for a number of nonstructural and structural applications Additional Reference 11–29 in product lines ranging from panels for interior covering 11–1 General Technical Report FPL–GTR–282 Table 11–1. Classification of wood- based compositesa Veneer based material Plywood Laminated veneer lumber (LVL) Parallel-strand lumber (PSL) Laminates Glue laminated timbers Overlayed materials Laminated wood–nonwood compositesb Multiwood composites (COM-PLYc) Composite material Fiberboard (low-, medium-, or high-density) Cellulosic fiberboard Figure 11–1. Common wood elements used in wood-based Hardboard composites from top left, clockwise: shavings, sawdust, Particleboard fiber, large particles, wafers, and strands. Waferboard Flakeboard Oriented strandboard (OSB) Laminated strand lumber (LSL) Oriented strand lumber (OSL) Wood–nonwood composites Wood fiber–polymer composites Inorganic-bonded composites Cellulose nanocomposites aAdapted from Maloney (1986). bPanels or shaped materials combined with nonwood materials such as metal, plastic, and fiberglass. cRegistered trademark of APA–The Engineered Wood Association. fiberboard. Specialty composites are also discussed. Figure 11–2. Wood-based composites used in the The second section covers structural composite lumber Centennial Research Facility at the Forest Products and timber products, including glued laminated timber, Laboratory. Glulam timbers support composite I-joists and laminated veneer lumber, parallel strand lumber, laminated plywood sheathing. (Photo by Steve Schmieding, Forest Products Laboratory.) strand lumber, and oriented strand lumber. Wood–nonwood composites are discussed in the third section, including purposes to panels for exterior uses and in furniture and inorganic-bonded composites and wood-thermoplastic support structures in many different types of buildings composites. Books have been written about each of these (Fig. 11–2). categories, and the constraints of this chapter necessitate that the discussion be general and brief. References are This chapter describes the general composition of wood- provided for more detailed information. based composite products and the materials and processes used to manufacture them. It describes conventional wood- based composite panels and structural composite materials Conventional Wood-Based intended for general construction, interior use, or both. Composite Panels This chapter also describes wood–nonwood composites. Conventional wood-based composites are used for a number The mechanical properties of these types of composites are of structural and nonstructural applications, including panels presented and discussed in Chapter 12. Because wood-based for exterior uses, panels for interior uses, and furniture. composites come in a variety of forms, we briefly describe Performance standards are in place for many conventional several of the most common commercial products. wood-based composite products (Table 11–2). This chapter is organized into three sections. The first Conventional wood-based composites are manufactured section covers conventional wood-based composite panels. products made primarily from wood with only a few percent Woody material types, adhesives, and additives common resin as the bonding agent. Product types of conventional to conventional wood-based composites are summarized. wood-based composites made from various constituent Specific products addressed include panel products such materials can be sub-categorized based on the physical as plywood, oriented strandboard, particleboard, and 11–2 CHAPTER 11 | Wood-Based Composite Materials Table 11–2. Commercial product or performance standards for conventional wood-based composites Product category Applicable standard Name of standard Source Plywood PS 1–09 Voluntary product standard PS 1–09 APA 2010a structural plywood PS 2–10 Voluntary product standard PS 2–10 APA 2010b performance standard for wood-based structural-use panels HP–1–2016 American national standard for hardwood DHA 2016 and decorative plywood ANSI/HPVA HP-1-2016) Oriented strandboard (OSB) PS 2–10 Voluntary product standard PS 2–10 APA 2010b performance standard for wood-based structural-use panels Particleboard ASTM D7033–14 Standard practice for establishing design ASTM 2014 capacities for oriented strand board (OSB) wood-based structural-use panels ANSI A 208.1–2016 Particleboard standard CPA 2016a Fiberboard ANSI A 208.2–2016 MDF standard for interior applications CPA 2016b ANSI A 135.4–2012 Basic hardboard CPA 2012a ANSI A 135.5–2012 Pre-finished hardboard paneling CPA 2012b ANSI A 135.6–2012 Engineered wood siding CPA 2012c ANSI A135.7-2012 Engineered wood trim CPA 2012d ASTM C208–12(2017) Cellulosic fiber insulating board ASTM 2017a Glued-laminated timber (glulam) ANSI A190.1-2017 Standard for Wood Products—structural APA 2017 glued laminated timber Structural composite lumber ASTM D3737-2018 Standard practice for establishing ASTM 2018 (including laminated veneer allowable properties for structural glued lumber (LVL), laminated strand laminated timber (glulam) lumber (LSL), and parallel strand ASTM D5456–19 Standard specification for evaluation of ASTM 2019a lumber (PSL)) structural composite lumber products configuration of the wood elements used to make these A useful way to classify conventional wood-based products: veneer, particle, strand, or fiber. Morphology of composites based on material characteristics is shown in the wood elements influences the properties of composite Figure 11–4. It presents an overview of the most common materials and can be controlled by selection of the wood types of commercial products discussed in this chapter and raw material and by the processing techniques used to a quick reference to how these composite materials compare generate the wood elements. Composite properties can to solid wood from the standpoint of density and general also be controlled by segregation and stratification of processing considerations. The raw material classifications wood elements having different morphologies in different of fibers, particles, and veneers are shown on the left layers of the composite material. In conventional wood- y-axis. Specific gravity and density are shown on the top based composites, properties can also be controlled by use and bottom horizontal axes (x-axes), respectively. The right of adhesives with different cure rates in different layers. y-axis, wet and dry processes, describes in general terms Varying the physical configuration of the wood element, the processing method used to produce a particular product. adjusting the density of