Stato dell`arte della Simulazione di Materiali Compositi

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Stato dell`arte della Simulazione di Materiali Compositi
Stato dell'arte della Simulazione di Materiali
Compositi
Composites Structures: Civil Airplanes Applications
Boeing 787
Airbus A350
In black the composite parts
Composites Structures: Automotive & Marine
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Composites Structures: Manufacturing & Civil
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MSC Software: A Global Team
Ann Arbor
Pune
Corporate Headquarters
Munich
Tokyo Beijing
Paris
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•
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More than 10 000 customers
More than 1000 employees
More than 48 years experience
More than 200 Business Partner
Partnered with the industry majors to
deliver software which fits with
customer processes
Introduction to Composites: Technologies
• The attractiveness of composites lies in their mechanical properties; such
as weight, strength, stiffness, corrosion resistance, fatigue life. That is
why the analysis of composite structures is imperative for the industries.
The main advantage of composites is their flexibility in design. Mechanical
properties of the laminate can be altered simply by changing the stacking
sequence, fibre lay-up and thickness of each ply which leads to
optimization in a design process.
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Classical Lamination Theory (CLT)
• Laminate effective material properties
are tailored to meet performance
requirements through the use of
lamination theory integrated in the
MSC.Software products.
• Used to accurately predict laminate
properties. These analysis methods
address:
• Stress-strain relationship for
membrane and bending response
• Thermal and moisture effects
• Inelastic behavior
• Strength and failure
• Interlaminar stresses
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θ=0º, t=0.01
θ= 45º, t=0.0125
θ= -45º, t=0.01
θ= 90º, t=0.0125
θ= 90º, t=0.01
θ= -45º, t=0.0125
θ= 45º, t=0.01
θ= 0º, t=0.0125
First-Ply-Failure Analysis
• First-Ply Failure (FPF)
– Linear analysis based on failure theory
– Compute failure index or strength ratio
for the ply material
– Optimization of ply angle/thickness
Critical Margin of Safety
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Going Beyond First-Ply-Failure
• Evaluate the load redistribution in a composite structure as the plies
fail progressively
• Simulate delamination growth from initial flaw
• Study crack propagation to design for fail-safe
structures
CZM
VCCT
Delamination
PFA
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Progressive Failure Analysis
• The progressive failure analysis is a method developed for predicting the
nonlinear response and failure of laminated composite structures from
initial loading to final failure.
• Failure is indicated by the failure criteria used.
• When failure occurs, the FEM element stiffness is degraded.
• The material will not heal; the damaged elements keep the degraded
properties after unloading.
• Investigations of effect of overloads on composite structures
Progressive Failure Analysis
• Once the strains and stresses are known throughout the composite
laminate, a failure theory is used to detect failures for each lamina at a
given load level, when failure index is larger than one, degrade
material stiffnesses
• Available for existing criteria:
Hill
Tsai-Wu
Hoffman
• Available for NEW criteria:
These failure theory are able to predict the failure load and also the
mode of failure such as fiber failure and/or matrix failure.
Puck
Hashin
Hashin-tape
Hashin-fabric
Progressive Failure Analysis
• How does failure affect the different material moduli ?
• Assume
– 1-direction is fiber direction
– 2-direction is matrix direction in the plane of the ply
– 3-direction is through the ply thickness
• Fiber failure
– Reduce E1 and E3
• Matrix failure
– Reduce E2, G12, G23 and G31
Progressive Failure Analysis
Rigid elliptical cylinder hitting
composite shell
5-layered composite
Puck criterion,
PFA with element
deactivation to simulate
crack propagation
Micromechanical Composite Material Definition
• Integrated structural analysis
software suite to predict strength,
reliability and durability of
structural composite components
• Based on constituent properties,
Fiber and Matrix, evaluates the
structural and material response
including degradation of material
properties due to initiation and
growth of damage.
• Over 20 Micro Mechanical Failure
Criteria Failure Criteria available
with Nastran Adv. PFA analysis
Advanced Progressive Failure Analysis:
Failure Theories
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Longitudinal tension
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Fiber micro-buckling
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Longitudinal compression
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Tsai-Wu theory
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Transverse tension
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Hill theory
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Transverse compression
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Hoffman theory
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Normal tension
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Maximum stresses theory
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Normal compression
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Maximum strain theory
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In-plane shear
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First strain invariant failure
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Transverse normal shear
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Longitudinal normal shear
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Inter-ply relative rotation
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Modified distortion energy
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Fiber crashing
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Inter-ply relative rotation
theory
Honeycomb failure modes recognized
Wrinkling
Crimping
Dimpling
Modeling composite materials at constituent Level
Fusolage Stiffened Panel Adv. Progressive Failure Analysis with Micromecanical material definition (Fiber / Matrix)
Stress Strain
Micromechanical Damage Index
Glued Contact between frames and panel
3D composites
Continuum Elements are required for Composites Modelling:
• When detailed out-of plane stress recovery are needed
• When transverse shear effect are predominant
• When accurate interlaminate stresses such near localized
region of complex loading or geometry
• When better contact condition are needed
3D composites
Detailed out-of plane stress recovery
Delamination Introduction
Delamination is one of the main failure mechanisms in laminated composites
Possible reasons for delamination are:
Manufacturing defects and stress
Gradients near geometric discontinuities (like stiffener terminations and
bolted joints)
• Delamination may result in local failure or even a significant loss of the
structural integrity
• Three different approach available:
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– VCCT
– CZM
– Breaking glued contact
Fracture Mechanics with VCCT
(Virtual Crack Closure Tecnique)
• The VCCT is the fracture mechanics approach for studying delamination
and crack initiation and growth.
• It is used for calculating the energy release rate of single or multiple
cracks.
Fracture Mechanics with VCCT
(Virtual Crack Closure Tecnique)
• In linear fracture mechanics, a crack starts to grow when
– Total G > Gc
– G is the energy release rate
– Gc is the fracture toughness
• VCCT is a methods used to compute the energy release rate.
• Energy release rate:
G = Fu/2a
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Fracture Mechanics with VCCT
(Virtual Crack Closure Tecnique)
Mode I:
Opening
Mode II:
Sliding
Mode III:
Tearing
VCCT Examples:
VCCT with Remeshing
VCCT without Remeshing
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Delamination:
Cohesive Zone Modeling (CZM)
• The so-called interface elements can be used to simulate the onset and
progress of delamination. The constitutive behavior of these elements is
expressed in terms of tractions versus relative displacements between the
top and bottom edge/surface of the elements.
• Considering a 3-D interface element, the relative displacement
components with respect to the local element system:
Delamination:
Cohesive Zone Modeling (CZM)
• The interface elements can be modeled between 2D and 3D structural
finite elements:
• The effective traction is introduced as a function of the effective opening
displacement, and is characterized by an initial reversible response
followed by an irreversible response as soon as a critical vc effective
opening displacement has been reached. Three standard functions are
currently available
Cohesive Zone Modeling: examples
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Delamination:
Breaking glued contact
• Release glued contact when stress criteria is satisfied:
• Use contact normal and tangential stress
• After break, do regular contact with friction and
separation
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Breaking glued contact: examples
• Coating debonding
• Load with rigid
body
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Curing Simulation
• Thermosets used as matrices in fibrous composites
• Cure is the reaction that transforms the matrix from a liquid oligomer to a
cross linked glassy polymer
• Cure is initiated by increased temperature
• Cure leads to chemical shrinkage
• The progress of the reaction is characterised by the degree of cure (α)
• Prediction is critical for predicting final shape
• Four Cure Kinetics models implemented in MSC.Software technology:
Cure kinetics model 1: by Lee, Loos and Springer
Cure kinetics model 2: by Scott
Cure kinetics model 3: by Lee, Chiu, and Lin
Cure kinetics model 4: by Johnston and Hubert
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Curing Simulation
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Springing in Crowning and Twisting
Conclusions:
• MSC.Software expertise is proven by the collaboration with all main
global players in the composites material market
• MSC.Software solutions are already succefully applied in any stage of
composites products development:
– Conceptual Design
– Optimization
– Manufacturing
• MSC.Software local team is highly
experienced in delivering and
implementing our solutions to customers
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Largest Autoclave in the
World
Statistics:
Inside working diameter: 30ft. (9.26M)
Ouside diameter: 32ft. (9.88M)
Inside working length: 76 ft. (23.5M)
Overall length: 112 ft. (34.5M)
Vessel volume: 82,000 cu.ft.
Max temperature: 450F
Max pressure: 150 psig
Vought Aircraft in Charleston, SC
Armando Mete
Account Manager Aerospace Industry - Italy
+39 06 42272249
+39 3357851319
[email protected]
http://www.mscsoftware.com/
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