146
7 Virtual testing approach for sandwich panel joints
It is assumed that stage ② represents the initiation of shear damage of the faces due to
shear plasticity, which typically leads to a quadratic stress-strain relationship (see section
5.2). However, catastrophic failure occurs suddenly, almost brittle unlike pure shear failure, which is characterized by considerable plasticity before failure. Therefore, it is assumed that compressive face failure in direction of the load eventually leads to catastrophic failure of the specimens in stage ③. The observed adhesive damage is likely to
be confined to the post failure regime in stage ④. Therefore, there are two relevant
mechanical effects, face shear damage and face compressive failure. In sum, Phase 1
reveals that the damage progression in this in-plane reference test is mostly governed
by the faces and to lesser extent by the adhesive. Due to its low in-plane mechanical
properties, the core has little impact on the global structural behavior. Therefore, it is
not necessary to model the core in detail. However, it is required to represent the specimen with a 3D-continuum model in order to enable the non-symmetric load introduction and thus the actual stresses in face sheet and potting. Regarding the solver, the
model is implemented based on explicit time integration in order to be able to adopt
model parameters from the previous out-of-plane tension test. With the model framework established in Phase 2, the subsequent model development phase requires only
two investigations, since the adhesive and face sheet material models can be adopted
from the modelling database. On constituent level there is an investigation for the implementation of a 3D-continuum model of the core required, since the modelling database only contains a detailed material model for the core at this point. This investigation
is described in section 4.1.4. on page 59, while the derived material model is given as
ABAQUS input deck in appendix A1.
2. Definition of model
framework
3D-continuum model
Explicit solver
1. Problem analysis
Prediction of
catastrophic failure
2-4h computational time
Two relevant mechancial
effects
3. Model development
Two additional
investigations
Face sheet and adhesive
properties adopted from
modelling database
4. Application of virtual
test method
Parameter studies
Evaluation of design
alternatives
Structural elements
Constituents
Level 1
Level 2
Level 3
Model synthesis
Constituents
Structural elements
Sub-component
3D-continuum core model -
ABS 5035-A4
Modelling database
Adhesive material
model
Delo
Face sheet
material model
ABS 5047-07
1
2
Figure 116 Summary of applied virtual testing approach for partially potted inserts under shear
7 Virtual testing approach for sandwich panel joints
It is assumed that stage ② represents the initiation of shear damage of the faces due to
shear plasticity, which typically leads to a quadratic stress-strain relationship (see section
5.2). However, catastrophic failure occurs suddenly, almost brittle unlike pure shear failure, which is characterized by considerable plasticity before failure. Therefore, it is assumed that compressive face failure in direction of the load eventually leads to catastrophic failure of the specimens in stage ③. The observed adhesive damage is likely to
be confined to the post failure regime in stage ④. Therefore, there are two relevant
mechanical effects, face shear damage and face compressive failure. In sum, Phase 1
reveals that the damage progression in this in-plane reference test is mostly governed
by the faces and to lesser extent by the adhesive. Due to its low in-plane mechanical
properties, the core has little impact on the global structural behavior. Therefore, it is
not necessary to model the core in detail. However, it is required to represent the specimen with a 3D-continuum model in order to enable the non-symmetric load introduction and thus the actual stresses in face sheet and potting. Regarding the solver, the
model is implemented based on explicit time integration in order to be able to adopt
model parameters from the previous out-of-plane tension test. With the model framework established in Phase 2, the subsequent model development phase requires only
two investigations, since the adhesive and face sheet material models can be adopted
from the modelling database. On constituent level there is an investigation for the implementation of a 3D-continuum model of the core required, since the modelling database only contains a detailed material model for the core at this point. This investigation
is described in section 4.1.4. on page 59, while the derived material model is given as
ABAQUS input deck in appendix A1.
2. Definition of model
framework
3D-continuum model
Explicit solver
1. Problem analysis
Prediction of
catastrophic failure
2-4h computational time
Two relevant mechancial
effects
3. Model development
Two additional
investigations
Face sheet and adhesive
properties adopted from
modelling database
4. Application of virtual
test method
Parameter studies
Evaluation of design
alternatives
Structural elements
Constituents
Level 1
Level 2
Level 3
Model synthesis
Constituents
Structural elements
Sub-component
3D-continuum core model -
ABS 5035-A4
Modelling database
Adhesive material
model
Delo
Face sheet
material model
ABS 5047-07
1
2
Figure 116 Summary of applied virtual testing approach for partially potted inserts under shear