Respected Professor,

I know i am bit late to add to this discussion but Please reply if possible as i am knew to VAM and really want to learn.

While going through your papers (''Asymptotic construction of Reissner-like composite plate theory with accurate strain recovery'' and few others) ,I noticed that you ususally do some transformation into reissner model although in the Neoclassical plate theory by Hodges et.al ("Application of the Variational-Asymptotical Method to Laminated Composite Plates") they included the shear strain in the 3-D strain term itself ,In the similar manner 3-D elasticity formulation is done in a paper by Peereswera et.al(Prediction of inter-laminar stresses in composite honeycomb sandwich panels under mechanical loading using Variational Asymptotic Method)

So i just want to understand are these two different theories or the same ,if same then why do we need to go through transformation part.

also some links in above discussion doesn't work any more if possible plase provide updated links.

A student just made a chart for comparing the sectional capability of ABAQUS and VABS. Please refer to http://hifi-comp.com/Documents/ABAQUSvsVABS_CrossSectionalCapabilities.pdf for more details.

If you are interesting in learning more about this powerful technique you can see the following references:

1 ) Generalized Unified Formulation applied to displacement-based theories for composire structures (Advanced Shear Order Deformation Theories, Zig Zag Theories and Layerwise Theories; note that an infinite number of theories is included in the GUF framework and all these formulations can be generated from SIX invariant 1 X 1 arrays):

L. Demasi, An Invariant
Model for any Composite Plate Theory and FEM Applications: the Generalized
Unified Formulation , Presented at the 50th AIAA/ASME/ASCE/AHS/ASC
Structures, Structural Dynamics & Materials Conference, Palm Springs,
California, 4-7 May 2009.

2) Generalized Unified Formulation applied to the mixed theories based on Reissner's Mixed Variational Theorem (RMVT) (formulation in which all the mixed theories are generated from 13 invariant 1X1 arrays):

L. Demasi, ∞6 mixed plate theories based on the
Generalized Unified Formulation. Part I: Governing Equations Composite
Structures, Vol. 87, (2009), 1-11.

3) Generalized Unified Formulation applied to RMVT-based Layerwise theories for composite structures:

L. Demasi, ∞6 mixed plate theories based on the
Generalized Unified Formulation. Part II: Layerwise theories Composite
Structures, Vol. 87, (2009), 12-22

4) Generalized Unified Formulation applied to RMVT-based Advanced Mixed High Order Shear Deformation theories and quasi-layerwise theories:

L. Demasi, ∞6 mixed plate theories based on the
Generalized Unified Formulation. Part III: Advanced Mixed High Order Shear
Deformation Theories Composite Structures, Vol. 87, (2009), 183-194

5) Generalized Unified Formulation applied to RMVT-based Zig-Zag theories:

L. Demasi, ∞6 mixed plate theories based on the
Generalized Unified Formulation. Part IV: Zig-Zag Theories Composite
Structures, Vol. 87, (2009), 195-205

6) RMVT-based theories and their numerical performances compared against the elasticity solution:

L. Demasi, ∞6 mixed plate theories based on the
Generalized Unified Formulation. Part V: Results Composite Structures,
Composite Structures, Vol. 88, (2009), 1-16.

If you are interested in a PhD opportunity on these and other topics please contact me at the following address ldemasi@mail.sdsu.edu

http://attila.sdsu.edu/~demasi/default.htm

Hi,

If you are interested in the assessment of VAPAS via GUF, I and professor Yu published a conference article on the subject:

L. Demasi, Yu W., “
Assess the Accuracy of the Variational Asymptotic Plate and Shell Analysis
(VAPAS) Using the Generalized Unified Formulation (GUF)”, Presented at
the 50th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials
Conference, Palm Springs, California, 4-7 May 2009

Luciano

http://attila.sdsu.edu/~demasi/default.htm

I am not familar with ABAQUS and do not have access to this software at this moment. However, you are welcome to request VABS to compare for yourself. I am pretty confident that VABS will be better. I will appreciate if you can share your conclusion with us. I am not coming to this site very often. If somebody want a quicker reponse, please send me an email.

hi

please answer me,in 2D analysis of cross section,meshed cross section analysisi of abaqus is better or vabs?wich one,have better result at warpping?(in and out warping)

please answer me with reson,or test,or camparsion analysis witheen abaqus and vabs?

All,

If you are interested, you can request VABS through hifi-comp.com.

The limited version, VABS Lite, is free and the full version can be evaluated for free for three months.

Nice to see you too. The new job makes me busy...but who is not busy?

http://www.engineering.sdsu.edu/aerospace/luciano.html

Luciano,

Nice to see you have also signed up for Imechanica. How is your new job? Must be very busy!

Wenbin

If your desire is to have the transverse stresses a priori and without the integration of the indefinite equilibrium equations you can use a mixed vartiational statement such as Reissner's.

Dear Dr.Bin,

Thanks a lot for your clarifications. Currently I am doing research in the field of higher order shear deformation theories, I am unable to share my results with you.

Regards

Subramanian

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Subramanian,

Again, I appreciate your comment. The sentence you pointed out states that
based on a priori assumptions a whole spectrum of models can be developed
ranging from the very simple one, Classical Lamination Theory (CLT), to very
complex ones, Higher-Order Layerwise Theories (HOLT). It does not say that
there are no models having better accuracy than CLT and simpler than HOLT. Of
course there are some models in between such as first-order shear-deformation
theory, higher-order shear deformation theory, zigzag theories. This discussion
is more relevant to VAPAS, a sister code of VABS. We have compared our code with
a zigzag-based model in ref. [1], the results of which support the sentence you
pointed out. We have plans to compare with the Generalized Unified Formulation
of Prof. Luciano Demasi at SDSU in the near future. If you are interested, I will
be very glad to collaborate with you to test the performance of either VABS or
VAPAS against your models.

[1] Yu, W.; Kim, J. S.; Hodges, D. H.; and Cho, M.: "Assessment of Two
Reissner-Mindlin Type Models for Composite Laminated Plates," Aerospace
Science and Technology , vol. 12, no. 5, 2008, pp. 408-417. (pdf)

Dear Subramanian,

Thanks for your interest. Yes VABS can accurately predict transverse shear and normal stresses without integrating the equilibrium equations. We did a 20-layer example. VABS calculates almost the same results as ANSYS using 3D elements. Please refer to the following paper for more details.

Yu, W. and Hodges, D. H.: "Generalized Timoshenko Theory of the Variational Asymptotic Beam Sectional Analysis, " Journal of the American Helicopter Society, vol. 50, no. 1, 2005, pp. 46-55. (pdf)

Dear Ben,

Your website says "either too simple (CLPT) or too complex (higher order layerwise theories). ........................... thepredictability is not guranteed because". This seems to be incorrect. I have developed a set of simple and highly accurate higher oder shear deformation theories for the analysis of laminated composite structures.

Subramanian

I would like to ask the following question regarding VABS.

Is VABS capable of accurately predicting transverse shear and normal stress across the thickness of laminated composite beam without integrating the equilibrium equations?.

Subramanian