Strengthening mechanical properties of glulam with Basalt Fiber.
Timber is the most ancient and widely used traditional construction material. Glued laminated (glulam) timber material has been in existence since the 1800s . It has been used in numerous applications including arches for airplane hangers, timber for floors, dome structures, timber bridge decks etc.
The earliest recorded studies on wood beams reinforced with fibre and FRP materials were in 1964 and 1965 by Wangaard  and Biblis  respectively when they studied the effect of bonding unidirectional fibre-glass/ epoxy reinforced plastic to the compression and tension faces of wood cores of various species and Theakson  in 1965 studied the feasibility of strengthening both laminated and solid wood beams with fibre-glass. In 1974, Krueger  studied laminated timber reinforced in the tension zone with a composite of high-strength bronze coated woven steel wire and epoxy. Later in 1981, Spaun  studied finger-jointed western hemlock cores reinforced with wood veneers and fibre-glass roving.
By the 2000s, better enhanced FRP composites called hybrid FRP and Ultra hybrid FRP composites were being developed and more research work into their uses were made. Fiorelli and Dias in 2002  analysed the strength and stiffness of timber beams reinforced with carbon fibre and glass fibre composites. Lopez-Anido and Xu  that same year published work they had done on the structural characterization of hybrid FRP-glulam panels for bridge decks.
In 2006 Dempsey and Scott  studied the effects of mechanically fastening FRP strips to wood members as a strengthening feature. That same year, Johnsson, Blanksvard and Carolin  worked on some glulam members strengthened by carbon fibre reinforcement by first running pull-out tests on four pairs of glulam members at four different anchoring lengths.
Xiongchen Fu studied the bonding performance between BFRP (Basalt fiber reinforced polymer) and timber , the results shows that: the treatment of wood surface greatly enhanced the bonding performance between BFRP and wood composite materials by HMR(hydroxy methylated resorcinol). The stripping rate reached 0.00% to 1.03% on the layer between wood composite and the BFRP which is treated by HMR, and it reached the ASTM D2559 standard requirements (outdoor structure with a laminated strip ratio <1%).
In 2008, Li Yunfeng, etc. studied the bonding performance of BFRP-Structural laminated timber, the results shows that the time is a greatly important factor for the bonding performance of BFRP-Structural laminated timber, while the unit pressure and the amount of glue still need further test to be determined . In 2010, Li Long, Zhang Peng-Yi studied the bonding performance of BFRP-bamboo-wood composite laminated glulam, the large daters shows the optimum gluing process of BFRP-bamboo-wood composite laminated glulam by Polyurethane adhesive .
1.1 Basalt FRP
The bonding experiment used was Basalt Fiber, which is a basalt fiber directional sheet, of thickness 1.4[+ or -]0.01mm made by Hicome in Nanjing, and designed for the strengthening of structural members against tensile, shear and impact forces. The mechanical properties of the basalt fiber had been measured in the experiment. The sheet is supplied with Vinyl resin and forms the Basalt Fiber Externally Bonded Reinforcement System.
The strengthened glulam material consisted of 48 Larch laminate sections, prepared for bonding experiment and flexural testing; 24 samples were cut in lengths of 1000mm with widths 50 mm, and other 24 samples were cut in lengths of 500mm with widths 50 mm The thickness of the laminate material used was 25mm, which is provided by IKEA Wood in Mohe.
1.3 Adhesives and Coupling Agents
Two types of adhesives were prepared, one is Resorcinol Adhesive, and the other is Polyurethane Adhesive. Both were provided by related company. Coupling agent is constituted by Formaldehyde, Sodium dodecyl sulfate, Sodium hydroxide, Resorcinol, and water. They were purchased in the chemical store.
2. SPECIMENS PREPARATION
The laminate materials were cut to sizes consisting three beam members for width and cleaned with aid of a sharp sand paper to ensure a flat, clean and degreased surface. Saw dust particles were removed with the aid of a hand vacuum cleaner. Likewise, the BFRP reinforcing material was cut to the same widths as the beams and vacuumed ready for application.
The coupling agent was made up at the specified ratio, and then, the coupling agent applied with the aid of a roller onto the surface of BFRP and laminate materials. They were then left to place in the next 24 hours.
The BFRP was then placed onto the tension face of the ply beam at equidistance from the beam centre line and set firmly onto the substrate using a suitable hand roller. The specimens were then formed on through different bonding processes. The following picture is a schematic diagram of the Bonding Process.
[FIGURE 1 OMITTED]
3. TEST PROCEDURES
Six groups BFRP samples in universal mechanical testing machine for BFRP bending, inter-laminar shear, tensile test, which is shown in Figure 2, the inter-laminar shear performance of BFRP. The loading rate is 2mm per minute.
[FIGURE 2 OMITTED]
Each beam was placed on the inverted test rig on a clear base. The Strengthening side is close to the steady. An external load was applied on the either side of the beam centre line. A picture of the beam test arrangement is placed in Fig. 3. The beams were loaded to failure on the three point bending test apparatus; the load rate was 3mm per minute.
[FIGURE 3 OMITTED]
4. TEST RESULTS
Results from the first test showed that the mechanical properties of the basalt fiber had a good performance. The average Inter-layer strength was 252.69MPa, the average tensile strength was 940.00MPa, and the average bending strength was 1011.20MPa. Fig. 1 shows the process of testing.
Results from the second test showed that BFRP timber can significantly enhanced the elastic modulus and bending strength, while the corresponding deflection reduced, which is shown in Figure 4 and Table 2.
Statistics show that, the average tensile strength parallel to grain can reach 90MPa and the bending strength is about 90MPa for China's timber, while results show that the average tensile strength parallel to grain of Basalt Fiber can reach 940MPa, and the bending strength is 1011.20MPa. Therefore, it is greatly active and effective to use BFRP for enhancing the mechanical properties. And the results also proved the same conclusion.
Tests show that the strength of BFRP reinforced timber increased by 10% than the unreinforced timber, while the deflection of the specimen reduced by 16% under the conditions of the resorcinol adhesive. And the strength of BFRP reinforced timber increased by 15% than the unreinforced timber, while the deflection of the specimen reduced by 16% under the conditions of the resorcinol adhesive. This proves that the basalt fiber reinforced structural glulam effectively.
This paper has presented experimental results aimed at establishing the effectiveness of BFRP composite systems flexural strengthening of glulam beams. Two alternative length measurements and two different types of adhesive for the upgrading system have been investigated.
All twenty-four plywood beams were subjected to three-point loading and the upgraded ply beam lengths reached and exceeded the plastic collapse load of like-width un-strengthened ply beams.
Further investigations are currently pursued to examine various beam widths, strengthened with more than one layer of BFRP composites hoping to further improve the beam properties.
[FIGURE 4 OMITTED]
 Dagher, H. J., Kimball, T. E., Shaler S. M., & Abdel-Magid, B. (1996). Effect of FRP Reinforcement on Low Grade Eastern Hemlock Glulams. Proceedings of National Conference on Wood Transportation Structures, pp. 207213.
 Wangaard, F. (1964). Elastic Deflection of Wood-Fiberglass Composite Beams. Forest Product Journal, 14, 256-260.
 Biblis, E. J. (1965). Analysis of Wood-Fiberglass Composite Beams Within and Beyond the Elastic Region. Forest Product Journal, 15, 81-88.
 Theakston, F. H. (1 965). A Feasibility Study for Strengthening Timber Beams with Fibreglass. Canadian Agricultural Engineering Journal, (1), 17-19.
 Krueger, G. P. & Eddy, F. M. (1974). Ultimate Strength Design of Reinforced Timber: Moment-Rotation Characteristics. Wood Science, 6, 330-344.
 Spaun, F. D. (1981). Reinforcement of Wood with Fibreglass. Forest Products Journal, 13, 26-33.
 Fiorelli, J. & Dias, A. A. (2003). Analysis of the Strength and Stiffness of Timber Beams Reinforced with Carbon Fiber and Glass Fiber. Materials Research, (4-5), 6.
 Lopez-Anido, R. & Xu, H. (2002). Structural Characterization of Hybrid Fiber-Reinforced Polymer-Glulam Panels for Bridge Decks. Journal of Composites for Construction,-ASCE, 6, 194-203.
 Dempsey, D. D. & Scott, D. W. (2006). Wood Members Strengthened with Mechanically Fastened FRP Strips. Journal of Composites for Construction,-ASCE, 10, 392-398.
 Johnsson, H., Blanksvard, T., & Carolin, A. (2006). Glulam Members Strengthened by Carbon Fibre Reinforcement. Materials and Structure-ASCE, 40, 47-56.
 FU Xiongchen & SHEN Shijie (2005). Basalt Continuous Fiber Reinforced Plastic (BFRP) / Wood Composites. (Master's thesis). Beijing Forestry University, Beijing, China.
 LI Yunfeng, SHEN Shijie (2009). The Study of Basalt Fiber Reinforced Structural Timber-One-Component Polyurethane Glue Technology Research. (Master's thesis). Beijing Forestry University, Beijing, China.
 LI Long & SHEN Shijie (2011). The Technology Research of Basalt Fiber Reinforced Laminated Larch Timber. Forestry Machinery and Woodworking Equipment, 3, 31-36.
ZHANG Pengyi (1) *; SHEN Shijie (2); MA Chunmei (1)
(1) M.A. Major: Wood Science and Technology. Beijing Forestry University, Beijing, China
(2) Professor, Major: Wood Science and Technology, Beijing Forestry University, Beijing, China Corresponding author.
Received 17 September 2011; accepted 19 November 2011
Table 1 Average BFRP Mechanical Properties Results from Experiments Samples Bending Bending Tensile Tensile Modulus of Strength modulus of Strength Elasticity (GPa) (MPa) Elasticity (GPa) (MPa) 1 45.35 1004.74 46.33 947.78 2 39.14 940.65 47.91 974.83 3 42.61 1003.95 43.95 940.86 4 44.67 1073.60 50.09 944.76 5 42.10 999.30 47.55 921.92 6 45.51 1045.38 46.03 873.84 Average 43.23 1011.27 46.98 934.00 Results from the second test showed that BFRP timber can significantly enhanced the elastic modulus and bending strength, while the corresponding deflection reduced, which is shown in Figure 4 and Table 2. Table 2 Average Failure Load and Deflection Results from Experiments The type Specimen Average Failure Average Deflect of adhesive Description Load at Failure Resorcinol 76x50x500mm 14.52kN 7.39mm adhesive control 76x50x500mm 16.74kN 6.62mm BFRP 76x50x1000mm 11.20kN 15.20mm control 76x50x1000mm 13.19kN 12.10mm BFRP Polyurethane 76x50x500mm 18.39kN 6.78mm adhesive control 76x50x500mm 19.06kN 5.24mm BFRP 76x50x1000mm 16.11kN 13.52mm control 76x50x1000mm 17.97kN 11.09mm BFRP
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|Author:||Pengyi, Zhang; Shijie, Shen; Chunmei, Ma|
|Publication:||Advances in Natural Science|
|Date:||Dec 31, 2011|
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