Using Surface Modified E-Glass Fiber Cloths to Enhance Poplar Laminated Veneer Lumber Composites: Effects of Modification Conditions, Gluing Processes, Hot-Pressing Parameters, and Assembly Patterns on Physical-mechanical and Interfacial Properties

To develop construction and building materials from low-quality fast-growing wood, poplar laminated veneer lumber composites reinforced by E-glass fiber cloths (GFC) were prepared with phenol-formaldehyde adhesives. The GFCs were modified with γ-aminopropyltriethoxysilane solution (concentration: 0.8%, 1.3%, and 1.8%). Between each veneer, 260, 330, or 400 g/m2 adhesives were spread on one or both sides of veneers. The composites were hot-pressed under different temperatures (130, 145, and 160 °C) and gauge pressures (0.7, 1.2, and 1.7 MPa). The GFC dosages and positions in composites were varied. To evaluate the effects of variables on composites, analytical methods included the contact angle, scanning electron microscopy, and physical-mechanical measurements (flexural strength, flexural modulus, horizontal shear strength, internal bond strength, thickness swelling, and dip peel). The results showed that γ-aminopropyltriethoxysilane made GFC more hydrophilic and compatible with adhesives, enhancing their interfacial adhesion. Considering most of the physical-mechanical and interfacial properties, the optimum parameters for preparing composites were determined to be 1.3% (γ-aminopropyltriethoxysilane), 330 g/m2 (adhesive, double-sided gluing), 160 °C (temperature), and 1.2 MPa (pressure). Varying GFC dosages and positions in composites had positive or negative effects on different physical-mechanical properties. Models were developed to correlate flexural data with GFC dosages and positions.