Determination of Strength Characteristics of Construction Timber Strengthened with Carbon and Glass Fibre Composite Using a Destructive Method
Beams strengthened with a composite material consisting of carbon and glass fibre stabilised with two types of adhesives were evaluated. The primary objective was to determine the technical attributes of joints, the maximum bending strength capacity, deflection, and modulus of elasticity. The reinforcement fibres tested were based on carbon and glass fibre. Epoxy and polyurethane adhesives were used for stabilising the fibres on a spruce timber beam. Composite beams glued in both a prestressed and non-prestressed condition were tested and then compared with non-reinforced control beams. A four-point deflection pursuant to EN 408 (1995) was used in the determination of the strength of the load-bearing construction beams based on composites, consisting of a fibre type, adhesive type, and spruce timber. This approach was applied to define the size of the construction beams and process the measurement results. Reinforcing construction beams with fibres applied in a prestressed condition resulted in an increase in the bending strength capacity by 31.6 to 44.4% compared with a non-reinforced solid timber construction beam. These construction elements, strengthened with carbon and glass fibre composites glued with epoxy and polyurethane adhesives, are suitable for applications that require bending resistance perpendiculary to the glued joint direction.
Determination of Some Physical Attributes for Wooden Construction Elements Strengthened with Woven Wire Fiberglass
This study designed composite wooden construction elements strengthened with woven wire fiberglass netting and determined the technical attributes. Scots pine (Pinus sylvestris L.) was used in wooden layers, and woven wire fiberglass netting was used in intermediate layers. Layers were pressed with polyvinyl acetate (PVAc) D3 and Desmodur-VTKA adhesives to form 7 solid 13-layer laminated composite specimens. Experiments on 95 specimens determined density, bonding strength, bending resistance, and compression strength; solid and solid laminated wooden materials were tested and compared. BS EN 204 and BS EN 205 standards were complied with for bonding strength tests, TS 5497 EN 408 was used for densities, and TS 549 EN 408 was followed for bending resistance and compressive strength. Most factors, except for intermediate layer material in compressive strength and bending resistance tests perpendicular to the glue line, did not cause significant differences. Variables (adhesive, intermediate layer material) used for determining bending strength parallel to the glue line were effective. Polyurethane adhesive increased resistance to bending parallel to the glue line. These composite wooden construction elements supported with woven wire fiberglass netting could be advantageous for applications that require high bending resistance perpendicular to the glue line. However, these composites do not hold a compressive strength advantage.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.