Experimental Evaluation of the Employment of a Laminated Composite Material with Sisal Fibres as Reinforcement in Timber Beams

Timber is the oldest construction materials in the world, have been widely used in structures in addition to having a high longevity, if treated properly (maintenance). If this does not occur, the wood deteriorates due to the action of insects, fungi and other aggressive agents. There are several materials and techniques used to reinforce the damaged parts. This paper presents an experimental study ofEucalyptus grandis and Pinus elliiottiitimber beams rein forced with sisal fibres laminated composite materials. The composite material and the wood were prepared for testing. In order to simulate the defect, some parts were cracked. The study was to determine the maximum load (rupture) applied on the timberin the conditions: without defect, with defect and without composite and with defect and with composite, aiming to verify the efficiency of the laminate as reinforcement in the wooden beams. The experimental results indicate the possible use of the laminated composite as reinforcement, presenting considerable increase in the maximum strength supported by the timber when compared to unreinforced cracked condition, being more efficient for the Pinus elliiottii species.


Introduction
Beams are structural elements present in most of buildings. Among the usual materials engineering h ighlights the wood, to be from natural and renewable source, low density and good mechanical performance. Timber structures when not treated properly can present problems due to the attack of biological degrading agents that contribute to the loss of their physical and mechanical properties, comp ro mising the integrity of the structural components.
The study of repair and reinforcement in the structure of wood has been the focus of technical and scientific papers, aimed at developing viable solutions to be used in the recovery of the same [1][2][3][4][5][6][7].
Of the possible materials used as reinforcement and repair wooden structures stand out from the composites, because it is a material designed, in order to obtain a resultant mechanical properties superior to those of constituent phases [8].
With the purpose of developing alternatives as reinforcement in beams, this paper aims at the development and characterization of co mposite laminated polymer matrix reinforced with sisal fibres to be used as reinforcement in Eucalyptus grandis and Pinus elliottii timber beams. The wooden beams with and without the use of the composite laminate is tested in bending, by making use of the static three point bending tests, and comparing the ma ximu m strengths condition to the faultless timber, and defective unreinforced and reinforced, and faulty, making it possible to evaluate the efficiency of the manufacture composite.

Material and Methods
The raw material used is a vegetable fiber and sisal as reinforcement and resin epoxy as matrix fase. The laminate composite was manufacture with a layer. The fiber used was obtained fro m the Sisal co mpany (Brazil), with caution as the use of fibres fro m the same batch. The Pinus elliottii and Eucalyptus grandis timber used in the fabrication of the specimens was obtained in a local sawmill in São João del-Rei (M G-Brazil), having as a precaut ionary pre-screeni ng of samples free defects.
Brackets have been manufactured of cast iron with 225 mm by 160 mm wide synthetic enamel coated. The sisal  To elaborate the composite material, the volu me of the fibre should correspond to thirty precents of the total [8], and the remain ing seventy percents should correspond to the volume of resin. Fro m these data the total weight of resin to be applied in the co mposite was then calculated. Eight specimens of timber, four of each species, were made by sawing them pris matic shape with square cross section with dimensions60×2.5×2.5cm ( Figure 2). Four of these (two of each species) were damagein the centre of their bases, measuring 8×2.5×1cm (Figures 3b and 3c). Finally, two of the specimen defective (one for each species) have been reinforced with the laminate (Figure 3a) and its adhesion was performed by use of the resin wh ile maintaining a bonding with 10cm 2 of area of each side groove ( Figure 2c) and curing by seven days. For adhesion of the laminate to the timber (Figure 3d) was used in the same proportions resin used to manufacture the composite.
The mechanical bending tests were performed in an EMIC testing machine with loading speed of 1 mm/ min. The modulus of elasticity (E m ) and strength flexural modulus (f m ) of the specimenswithout defect (no failure) was obtained according to the Brazilian standard NBR 7190 [13], respectively expressed by Equations 1 and 2, F 10% and F 50% and 10% and 50% of ma ximu m load (F max ), L is the length of the useful parts (distance between supports) and b and hthe width and height measures of the cross section respectively.
The dimensions of the specimens follo wing the L≥21·h relation, neglecting the effect o f shear forces in the calcu lus of the displacements [20][21][22].

Results andDiscussions
Os testes realizados com as madeiras íntegras geraram fraturas frágeis (Figura 4a) e também por propagação de trincas (Figuras 4b, 4c e 4d). The tests performed with the wood cracked generated crack propagation precisely in points where there stress concentrators, as shown in Figure 5. Finally, tests carried out with the additional have differentfailure mechanis ms. While in the Pinus was disruption of the composite material ( Figure 6), there was a break in Eucalyptusspecies, which has subsequently damage the composite material (Figure 7).    Figure 8 it is noted that the intact samples shows the maximu m fo rce (F MAX ) higher than the strengthened, which in turn was superior to those at the specimens with defects.
It is also noted that Pinus support a load lower than the Eucalyptus in all conditions tested, but can also be seen in Table 1. The cracks in Pinus provided an average drop in maximu m load in relation to intact timber about 82.96%, while the reinforcement was able to increase the maximu m load supported by 66.66% co mpared to flawless Pinus.Eucalyptus already cracked gave an average drop in maximu m load in relation to intact timber about 74.04%, while the reinforcement was able to increase the maximu m load supported by 18.52% co mpared to flawless Eucalyptus.Given the above, it appears that when the timber is not enhanced fracture during the imposition o f charges, the strengthening of the composite material has become mo re efficient. Table 2 shows the individual values of the modulus of elasticity in bending (E m ) and flexural strength modulus (f m ) obtained for the intact Pinus elliiottiiand Eucalyptus grandis timber.
In Table 2, the Eucalyptushad a higher modulus of elasticity and flexu ral strength modulus that Pinus timber.

Conclusions
Currently, researches are being directed to the production of laminates for structural reinforcement and low cost. These factors are affected by material selection, environ mental conditions of rolling, the characteristics of the tooling and manufacturing methodology.
After a few tests on the materials presented in this work, we can conclude that the flawless specimens had a considerable reduction of its resistance to bending in relation to the intact timber. The addition of natural fiber reinforcement allo wed reasonable increase in the flexural strength modulus of the flawless timber.
In future studies, we intend to evaluate other bonding areas, new timber species and the variation in the nu mber of layers used in the preparation of the composite.