Contact Information
Office: E-307
Phone: (619) 594 3752
FAX: (619) 594 0933
email: ldemasiATmail.sdsu.edu
Education
M.Sc., Aeronautical Engineering, Politecnico di Torino (Italy), 1999
Ph.D., Aeronautical Engineering, Politecnico di Torino (Italy), 2004
Research Interests
Nonlinear Equivalent Plate Model for Wing Systems
This research presents a comprehensive nonlinear
structural analysis method and simulation capability for equivalent
plate wing systems.
This work, through thorough correlation studies with commercial
Finite-Element codes such
as NASTRAN, maps the regions of applicability of equivalent-plate
modelling when nonlinear
composite wings are involved and leads to new understanding
regarding the numerical issues,
accuracy, and computational cost of nonlinear equivalent plate
methods considered earlier as
a potential important element in multidisciplinary design
optimization technology for airplane
conceptual design.
- Demasi L., Livne E., “Structural Ritz-Based Simple-Polynomial Nonlinear Equivalent Approach - An Assessment”, Journal of Aircraft Vol. 43, No. 6, 2006, pp. 1685-1697
- Demasi L., Livne E., “ Structural Ritz-Based Simple-Polynomial Nonlinear Equivalent Approach - An Assessment”, Presented at the 46th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, Austin, Texas, 18-21 April 2005
Dynamic Aeroelasticity and Aeroelasticity of Joined-Wings
This research focuses on the development of a new nonlinear Finite-Element
modelling capability for general thin-walled aerospace structures
undergoing large deformation and its
integration with Doublet Lattice Method
(and transformation to the time domain)
to create a nonlinear aeroelastic simulation capability.
The goal of this work is to allow aeroelastic
studies of Joined-Wings and other non-conventional airplane configurations,
where compression in major
lifting surfaces makes it necessary to model nonlinear structural behaviour.
The methodology and resulting computer tools are applicable to other
nonlinear aeroelastic systems
such as high-altitude long-endurance (HALE) vehicles.
- Demasi L., Livne E., “Dynamic Aeroelasticity of Structurally Nonlinear Configurations Using Linear Modally Reduced Aerodynamic Generalized Forces”, AIAA Journal, Vol. 47, No. 1, January 2009
- Demasi L., Livne E., “ Aeroelastic Coupling of Geometrically Nonlinear Structures and Linear Unsteady Aerodynamics: Two Formulations ”, Presented at the 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, Schaumburg, Illinois, 7-10 April 2008
- Demasi L., Livne E., “Nonlinear Aeroelastic Simulation Using Linear Modal Unsteady Aerodynamics - Two Time Integration Approaches”, Journal of Fluids and Structures, in press
- Demasi L., Livne E., “ Dynamic Aeroelasticity of Coupling Full Order Geometrically Nonlinear Structurs and Full Order Linear Unsteady Aerodynamic - The Joined Wing Case ”, Presented at the 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, Schaumburg, Illinois, 7-10 April 2008
- Styuart A., Demasi L., Livne E. and Lin K., “ Probabilistic Modeling of the Aeroelastic Life Cycle for Risk Evaluation of Composite Structures ”, Presented at the 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, Schaumburg, Illinois, 7-10 April 2008
- Demasi L., Livne E., “ Exploratory Studies of Joined Wing Aeroelasticity ”, Presented at the 46th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, Austin, Texas, 18-21 April 2005
Finite Element Applications and Theoretical Plate Models
In the analysis of multilayered composite plates the interlaminar continuity of the displacements and
transverse stresses must be taken into account.
This research addresses the formulation of new layerwise and higher order
plate theories. Both displacement-based and mixed variational statements are adopted.
To take into account the so called zig-zaf form of the displacements, improved zig zag models based on Murakami's zig zag
function are presented.
- Demasi L., “2D, quasi 3D and 3D Exact Solutions for Bending of Thick and Thin Sandwich Plates”, Journal of Sandwich Structures and Materials 2008, 10, pp. 271-310, doi:10.1177/1099636208089311
- Demasi L., “Quasi-3D Analysis of Free Vibration of Anisotropic Plates”, Composite Structures 2006, 74, pp. 449-457
- Demasi L., “Treatment of Stress Variables in Advanced Multilayered Plate Elements Based Upon Reissner's Mixed Variational Theorem ”, Computers & Structures 2006, 84, pp. 1215-1221
- Demasi L., “Refined Multilayered Plate Elements Based on Murakami Zig-Zag Functions”, Composite Structures 2005, 70, pp. 308-316
- Carrera E., Demasi L., “Two benchmarks to assess two-dimensional theories of Sandwich Composite Plates”, AIAA Journal Vol. 41, No. 7, pp. 1356-1362, July 2003.
Three Dimensional Elasticity Solution for Plates
This work focuses on the classical problem of
finding the elasticity solution of simply supported rectangular plates.
New alternative methods are presented. For the case of isotropic materials
an alegbraic formulation is developed. For the multilayered case the
imposition of interlaminar compatibility of the displacements and
equilibrium of the transverse stresses is naturally done with the adoption
of Mixed Form of Hooke's Law.
- Demasi L., “Three-Dimensional Closed Form Solutions and Exact Thin Plate Theories for Isotropic Plates”, Composite Structures 2007, 80, pp. 183-195, doi:10.1016/compstruct.2006.04.073
- Demasi L., “2D, quasi 3D and 3D Exact Solutions for Bending of Thick and Thin Sandwich Plates”, Journal of Sandwich Structures and Materials 2008, 10, pp. 271-310, doi:10.1177/1099636208089311
- Demasi L., “Three-dimensional closed form solutions and ∞3 theories for orthotropic plates ”, Mechanics of Advanced Materials and Structures, 2008, in press
Aerodynamics of Non-conventional Wing Configurations
This research focuses on
planar and non-planar wing systems.
In particular, the cases of C-wings and annular wings (which could represent Joined-Wings) are analyzed.
A new theoretical method for predicting minimum induced-drag conditions is
utilized. The procedure is based on lifting
line theory and the small perturbation acceleration potential.
Optimality conditions are formulated using the Euler-Lagrange integral
equation with constraints on fixed total lifting force and wing span.
Particular attention is paid to analysis and numerical treatment of
the Hadamard finite-part integrals involved in the solution process.
The minimum induced-drag problem is then formulated and solved numerically
and analytically. It is possible to demonstrate that
closed wing systems present aerodynamic advantages (reduced induced drag)
with respect to the traditional planar configurations.
- Demasi L., “Induced Drag Minimization: a Variational Approach Using the Acceleration Potential”, Journal of Aircraft, Vol.43, No. 3, 2006, pp. 669-680
- Demasi L., “Investigation on Conditions of Minimum Induced Drag of Closed Wing Systems and C-Wings”, Journal of Aircraft, Vol.44, No. 1, 2007, pp. 81-99
Curriculum and list of publications (PDF)
Current Research Projects
Dynamic aeroelasticiy, Advanced formulations for multifidelity models of composite structures
There are possibilities of joint research activities with Universities in Europe.
To inquire about research opportunities please send an email.
Are you interested in our Joint Doctoral Program? Please read here .