A.T. Marques

Flexural performance of polyester and epoxy polymer mortars under severe thermal conditions

Abstract A comparative study of the influence of thermal effects on flexural strength of two different binder formulations of polymer mortars was performed. For this purpose, specimens of unsaturated polyester and epoxy polymer mortars were exposed to a large range of temperatures, between −20 and +100 °C, and tested afterwards in bending. For each temperature level, flexural strengths at test temperature, and residual flexural strengths after temper, were determined. The strength degradation process occurring in the material, as a consequence of positive thermal fatigue cycles (+20 °C/+100 °C) and freeze–thaw cycles (−10 °C/+10 °C), was also quantified and analysed. Obtained results show the relevance of material properties assessment with temperature.

Modelling of concrete beams reinforced with FRP re-bars

Abstract A finite element analysis of reinforced concrete beams with fiber-reinforced plastic re-bars is performed. Corrosion of steel re-bars is a common problem encountered in the civil construction sector, due to the porosity of concrete. The use of fiber-reinforced polymers (FRP) instead of steel re-bars can lead to a better corrosion-resistant reinforced concrete with applications in many construction fields. The need for non-linear geometrical and material models implies the use of numerical methods such as the finite element method. In this paper the use of a first-order shear-deformation theory in the analysis of concrete shells reinforced with internal composite unidirectional re-bars is proposed. The theory is implemented in a shell element that allows for a layered discretization of the laminate materials. A perfect plastic and a strain-hardening plasticity approach are used to model the compressive behavior of the concrete. A dual criterion for yielding and crushing in terms of stresses and strains is considered, which is complemented by a tension cut-off representation. The material law for the unidirectional re-bars is linear elastic/brittle, whereas the concrete allows for elasto-plastic–brittle behavior. A simply-supported concrete beam, reinforced with composite re-bars is analysed. The effects of the reinforcement and the comparison of composite and steel re-bars on concrete are discussed. Comparison between numerical and experimental results is made for a RC beam reinforced with pultrusion rods.

A NDT assessment of fracture mechanics properties of fiber reinforced polymer concrete

An acoustic emission (AE) methodology has been used to measure the fracture toughness and associated energy using three point bending tests, according to the Two Parameter Model (TPM). The aim of this article is to identify how acoustic emission can measure the damage of polymer concrete and compare the fracture mechanics characteristics with concrete specimens. Polyester and epoxy resins were considered and glass fibers were used as reinforcement for the epoxy polymer concrete.

Tool Effects on Hybrid Laminates Drilling

Fiber reinforced plastics are increasing their importance as one of the most interesting groups of material on account of their low weight, high strength, and stiffness. To obtain good quality holes, it is important to identify the type of material, ply stacking sequence, and fiber orientation. In this article, the drilling of quasi-isotropic hybrid carbon +glass/epoxy plates is analyzed. Two commercial drills and a special step drill are compared considering the thrust force and delamination extension. Results suggest that the proposed step drill can be a suitable option in laminate drilling.

Advances in Thermoplastic Matrix Towpregs Processing

The present work reports the development of new technologies to fabricate long and continuous-fiber-reinforced composite structures from low-cost thermoplastic matrix semiproducts. These semiproducts, thermoplastic matrix towpregs and preconsolidated tapes (PCTs), were produced in a purposely-built prototype machine, by deposition of a thermoplastic polymer in powder form on continuous fibers. The work also presents the advances made in the processing of these materials into composites by conventional techniques, such as pultrusion, filament winding and compression molding. Finally, it describes the investigation of the optimal processing conditions that maximize the mechanical properties of the composites. These properties are good enough for the composites to be used as engineering materials in many structural applications.

Nonlinear Finite Element Analysis of Rubber Composite Shells

A finite-element solution for rubber composite shells is presented. Sandwich laminates with a rubber core have also been studied. Incompressibility of a rubber matrix and complexity of composite shells bring forth the need for a sound numerical model to describe the behavior of such engineering materials. The developed model was applied to a degenerate shell element within the limits of the first- and third-order shear deformation theories. The model allows to predict with a sufficient accuracy the nonlinear behavior of sandwich shells with composite skins and rubber cores and composite shells with a rubber matrix.

Impact of the geometry of inclusions at the micro-scale on the overall stochastic properties

ABSTRACT In this contribution, the establishment of relationships between the microstructure of the material and the macroscopic properties is numerically investigated. The material under study is composed by inclusions randomly distributed on a uniform matrix and its heterogeneous nature is characterized by the size, shape, spatial distribution, and properties of the inclusions. To conduct these analyses, a general framework that generates and simulates representative volume elements (RVEs) based on the commercial finite element (FEM) software ABAQUS and existing homogenization techniques is developed. Two- and three-dimensional RVEs are generated and the variation of the properties investigated using a statistical approach.

Modelling of fibre Bragg grating sensor plates

In this paper is presented the design of a composite sensor plate, based on fibre Bragg grating (FBG) sensors, to be used as alternative to the conventional electric strain gages. The use of such composite sensor plate will permit to profit of FBG sensors advantages compared to conventional electrical strain gages increasing its safety considering that they are commonly simply surface mounted in structure using adhesives.