Functionally graded fiber cements.

Author(s)

Cleber Marcos Ribeiro Dias

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2011-02-25

Examining board members

Vanderley Moacyr John; Vahan Agopyan; Aline da Silva Ramos Barboza; Geraldo Cechella Isaia; Emílio Carlos Nelli Silva

• Advisor: Vanderley Moacyr John

Abstract

The present study applies the functionally graded materials (FGM) concept on the development of fiber cements as an alternative to improve the mechanical performance and reduce cost of production of asbestos-free corrugated sheets. Primarily, this work establishes the concept of functionally graded fiber cement. Then, finite element modeling (FEM) is applied in the evaluation of the stresses distributions in corrugated sheets under bending and static wind loads. The simulations show that for these load cases, some regions of corrugated sheets are submitted to low stress intensities what justify the application of FGM concept for optimization of the strength distribution in such components. The experimental part of this work consists of four different studies: a) production of functionally graded fiber cements with gradation through thickness; b) development of a method for choosing formulations in functionally graded fiber cements; c) development of fiber reinforced cementitious composites for high speed extrusion and; d) pre-industrial application to evaluate the suitability of functionally graded fiber cements production. The first experimental study shows that functionally graded cementitious composites with 1.0% of PVA fibers, in mass, strategically distributed through thickness, presented similar modulus of ruptures (MORs) to that homogeneous ones with 1.8% of PVA fibers what proves that gradation of fiber content through thickness is a good approach to reduce cost of fiber cement pads without affecting the mechanical performance of the composite. The second experimental work examines sixcomponent fiber cement formulations employing the screening strategy which is a promising methodology to generate coherent mixture rules, optimize cost and performance and even facilitate the choosing of formulations for functionally graded fiber cements. PVA fibers and glass fiber reinforced cementitious composites for high speed extrusion were developed forpre-industrial application. Composites with 4.0% of alkali-resistant (AR) glass fiber, in volume, presented average tensile strength of 12.0 MPa while composites with 3.0% of PVA fibers presented 7.5 MPa. The application of these mixtures between layers of fiber cement corrugated sheets results in improvement of the performance of the product. (AU)

• FAPESP's process: 05/03943-7 - Development of fiber cements with functionally graded properties
• Grantee: Cleber Marcos Ribeiro Dias
• Support Opportunities: Scholarships in Brazil - Doctorate