Evaluation of the stiffening mechanism based on micro-sized particle inclusions in laminated composites

Rigid particles have been incorporated into laminated composites, especially to enhance their bending performance attributed to the stiffening of the matrix phase (i) and the increased interlaminar shear resistance (ii). In order to better evaluate the improvement mechanism provided by the particulate inclusions, this work investigates the incorporation of micro-sized silica on the top, bottom and both surfaces of glass fibre laminates, mitigating the interference of the interlocking effect. Three-point bending, and impact tests are performed to evaluate the hybrid glass fibre composites containing 5, 7.5 and 10 wt% of micro silica. In addition, the effect of the micro silica particles into epoxy polymers is verified under tensile, compressive and abrasion tests. A finite element model is developed to simulate the three-point bending test and to better assess the behaviour of the composite laminate. Although silica particles lead to increased compressive modulus of the epoxy polymers, their positive effect on glass fibre composites under flexural loads is more evident when placed on the bottom side of the laminates subjected to the maximum tensile stress. The incorporation of 7.5 wt% silica microparticles at the bottom surface of the laminates achieves higher flexural strength and lower impact resistance

Effect of siderurgical aggregates on concrete exposed to saline environments

ABSTRACT: Using recovered waste to obtain high-performance structural concrete is possible and justified by the saving in natural resources and the avoidance of deposit in landfills. The technical justification for these new and ecological concretes must be based on proving their mechanical performance and durability. The former has been widely studied, while the latter has been very vaguely studied, with controversies being found in this regard. This research aims to shed light on the ability of concrete with siderurgical aggregates to resist processes that lead to early deterioration or alteration of its microstructure. To this end, concrete with siderurgical aggregates and limestone reference concrete were subjected to traditional durability tests, as well as novel tests consisting of exposure to saline environments. The results obtained show that the concretes with siderurgical aggregates exhibit a similar behavior in terms of gas and water permeability, accelerated carbonation and resistance to freeze-thaw cycles (except for total replacements) to the limestone reference concrete. Exposure to a salt spray chamber and to seawater show the same effect in terms of chloride profiles, while the steel reinforcements embedded in the concrete did not suffer corrosion for any of the exposure times. These results open the door to using these concretes in maritime work, both onshore and offshore.This research was co-financed by the European Regional Development Fund (ERDF) and the Ministry of Economy, Industry and Competitiveness (MINECO) within the framework of the project RTC-2016-5637-3 and R&D project RES2020PU03 financed by the Department of Universities, Equality, Culture and Sports of the Government of Cantabria, Spain. The research was possible thanks to the collaboration of the company INGECID, the department LADICIM (University of Cantabria) and the companies ROCACERO and SIDENOR, as well as the Department of Universities and Research, Environment and Social Policy of the Government of Cantabria (Spain)

Alternative Methodology For Calculating The Modulus Of Elasticity Of Wooden Beams Of Structural Dimensions

This study aims to present an alternative calculation methodology based on the Least Squares Method for determining the modulus of elasticity in bending wooden beams of structural dimensions. The equations developed require knowledge of three or five points measured in displacements along the piece, allowing greater reliability on the response variable, using the statistical bending test at three points and non-destructively, resulting from imposition of measures from small displacements L/300 and L/200, the largest being stipulated by the Brazilian norm NBR 7190:1997. The woods tested were Angico, Cumaru, Garapa and Jatoba. Besides obtaining the modulus of elasticity through the alternative methodology proposed, these were also obtained employing the Brazilian norm NBR 7190:1997, adapted to the condition of non-destructive testing (small displacements) and for pieces of structural dimensions. The results of the modulus of elasticity of the four species of wood according to both calculation approaches used proved to be equivalent, implying the good approximation provided by the methodology of calculation adapted from the Brazilian norm.341153160(1997) Standard test method of static tests of lumber in structural sizes, , AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM). ASTM D 198. Annual book of ASTM standards, v. 03.01. West Conshohocken(1996) Standard test methods for mechanical properties of lumber and wood-base structural material, , AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM). ASTM D 4761-96. Annual book of ASTM standards. West Conshohocken(1997) Projeto de estruturas de madeira, , ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS (ABNT). NBR 7190. Rio de JaneiroBurdzik, W.M.G., Nkwera, P.D., Transverse vibration tests for prediction of stiffness and strength properties of full size Eucalyptus grandis (2002) Forest Products Journal, Madison, 52 (6), pp. 63-67Chou, Y., Polansky, A.M., Mason, R.L., Transforming non-normal data to normality in statistical process control (1998) Journal of Quality Technology, Milwaukee, 30, pp. 133-141Christoforo, A.L., Panzera, T.H., Batista, F.B., Borges, P.H., Rocco, F.A.L., Numerical evaluation of the longitudinal modulus of elasticity in structural round timber elements of Eucalyptus genus (2011) Revista Engenharia Agrícola, Jaboticabal, 31, pp. 1007-1014Dong, X.H., Hai, W.L., Comparative study on four different methods for measuring the dynamic modulus of elasticity of Acer mono wood (2011) Advances in Materials Research, New York, 160-162, pp. 384-388(1995), EUROPEAN STANDARD. Estruturas de madeira-Métodos de teste-Determinação das propriedades mecânicas de painéis derivados de madeira. Versão portuguesa. Bruxelas, (EN, 789)Fiorelli, J., Estudo teórico e experimental de vigas de madeira laminada colada reforçadas com fibra de vidro (2005), 108 f. Tese (Doutorado), Ciência e Engenharia de Materiais, Escola de Engenharia de São CarlosLiang, S., Fu, F., Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber (2007) Journal of Forestry Research, Colombo, 18, pp. 309-312Miná, A.J.S., Oliveira, F.G.R., Calil, C., Dias, A.A., Sales, A., Avaliação não destrutiva de postes de madeira por meio de ultra-som (2004) Scientia Forestalis, Piracicaba, (65), pp. 188-196Miotto, J.L., Dias, A.A., Produção e avaliação de vigas de madeira laminada colada confeccionadas com lâminas de Eucalipto (2009) Revista Tecnológica, Maringá, 18, pp. 35-45. , Edição EspecialMontgomery, D.C., (2005) Design and analysis of experiments, , Arizona: John Wiley & Sons, 6th edOliveira, F.G.R., Sales, A., Ultrassonic measurements in Brazilian hardwood (2002) Materials Research, São Carlos, 5 (1), pp. 51-55Pigozzo, J.C., Pletz, E., Lahr, F.A.R., Aspectos da classificação mecânica de peças estruturais de madeira (2000), In: VII ENCONTRO BRASILEIRO EM MADEIRAS E EM ESTRUTURAS DE MADEIRA, 7°, São Carlos. AnaisRocco Lahr, F.A., (1983), 216f Sobre a determinação de propriedades de elasticidade da madeira. Tese (Doutorado), Engenharia de Estruturas, Escola de Engenharia de São Carlos, Universidade de São Paulo, São Carlos, 1983Ross, R.J., Brashaw, B.K., Pellerin, R.F., Nondestructive evaluation of wood (1998) Forest Products Journal, Madison, 48 (1), pp. 14-19Sales, A., Candian, M., Cardin, V.S., Evaluation of the mechanical properties of Brazilian lumber (Goupia glabra) by nondestructive techniques (2011) Construction and Building Materials, Guildford, 25 (3), pp. 1450-1454Wang, S.Y., Chen, J.H., Tsai, M.J., Lin, C.J., Yang, T.H., Grading of softwood lumber using non-destructive techniques (2008) Journal of Materials Processing Technology, Amsterdam, 208, pp. 149-15