Browsing by Author "LOJA, M.A.R."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Exponentially graded auxetic structures: an assessment of the shear correction factor and static deflectionPublication . LOJA, M.A.R.; Barbosa, Joaquim I.This work aims to study the influence of the material and geometric parameters that characterize re-entrant hexagonal honeycomb auxetic structures in the maximum transverse static deflection of beams. In addition, this study considers the composition of the material through the thickness results from the mixture of a metallic phase and one of four different selected ceramics, using the exponential volume fraction law. The first-order shear deformation theory within an equivalent single-layer approach is used to assess the material and geometric parameters’ influence on the structures’ deflection. Considering this theoretical approach, the impact of the material and geometric parameters on the shear correction factors, calculated for each specific case, is also analyzed. The results allow us to conclude how the shear correction factors and the structures’ maximum static deflection are affected by the re-entrant hexagonal honeycomb auxetic cells’ aspect ratios, by the angle associated with the direction of the inclined members of the hexagonal cells and the use of materials with differentiated Poisson’s ratios.
- Modeling and analysis of Double-Double composite structures integrating piezoelectric materialsPublication . Lupu, Bogdan D.; LOJA, M.A.R.Multifunctional materials and structures are increasingly important for innovative structural solutions. This work aims to model such structures constituted by Double-Double composites and piezoelectric materials. Besides the homogenization trend of these laminates as the number of the replicating sub-laminates grows, other features include simple ply drop placement, and card sliding to potentially save weight. To control the mechanical response, piezoelectrics along with several types of stacking were considered. The first-order shear deformation theory implemented via the finite element method was used to assess the model, and a set of verification and parametric studies was developed, resulting in a good performance confirmation.
- A study on the static behavior of functionally graded I-shaped beamsPublication . LOJA, M.A.R.; Carvalho, André; Barbosa, InêsFunctionally graded materials are well-known for their ability to minimize abrupt stress transitions that are typical of laminated composites, as well as for being very suitable to operate in adverse high-temperature environments. They can act as thermal barriers if a proper selection of the constituent materials is considered. These materials and structures have attracted the attention of many researchers; however, previous research efforts have been focused on the systematic study of rectangular-shaped cross-section profiles. The use of beams characterized by other cross-sections, which are commonly used in metallic construction, may benefit from the continuous, smooth materials mixture that is typically found within functionally graded composites. Hence, this work aims to investigate the behavior of symmetrical, I-shaped, cross-section beams made from these advanced composites by performing a set of parametric analyses. These beams are modeled after solid finite elements to be able to describe the materials mixture evolution through the beam thickness with greater detail. Thick and moderately thick beams are submitted to static loading while considering different boundary conditions, and their linear static behavior is analyzed. As expected, the stress profiles are highly influenced by the materials' mixture profiles. Significant shear stress was found in the I-shaped cross sections.