MEC4446 Finite Element Analysis: Composite Shell Buckling Report

This report presents an analysis of the buckling behavior of a composite cylindrical panel with a circular hole, focusing on determining the first buckling load for various shell thicknesses and composite materials (Boron/Epoxy and Glass/Epoxy). The laminate code used is +-45ms, with each layer having a thickness of 0.0056 inches. The study investigates the effects of varying the number of layers ('m' from 1 to 5) and compares the buckling loads for Boron/Epoxy (70% fiber volume fraction) and Glass/Epoxy (45% fiber volume fraction). The geometry considered is a cylindrical panel with a radius of 15 inches and a length of 14 inches, featuring a centrally located 2-inch diameter hole. The analysis employs a 9-node shell element (S9RS) with a mesh producing 320 elements and 1344 nodes. The results show a progressive increase in buckling load with increasing laminate thickness for both materials, with Boron/Epoxy exhibiting significantly higher buckling loads compared to Glass/Epoxy for the same thickness, making it a better choice for aerospace applications requiring high buckling resistance.

Composite Structure
NAME
COURSE
UNIVERSITY/AFFILIATION
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Introduction
This particular analysis is all about the act of getting the first buckling load which is for the
problem for various thickness of the shell and also for the various materials of the composite.
The basic code for the laminate is +- 45ms. The thickness of each and every layer is also the
same and is 0.0056in. After checking the effects of the thickness of the shell, it was found that
the value of ‘m’ changes from 1 to 5. Also for the impacts of the various materials of the
composite, which includes the boron or the epoxy together with the volume fraction of the fibre
which is 70% and the glass or epoxy with the volume of the fraction of fibre which is 45%
The properties of the materials which is taken from the table are as follows:
Boron/Epoxy E1 is 29.6*106 lb/in2 ,
E2=2.7*106 lb/in2 ,
ν12=0.23,
G12= G23 =G31=0.81*106 lb/in2
Glass/Epoxy E1=5.6*106 lb/in2 ,
E2=1.2*106 lb/in2 ,
ν12=0.26,
G12= G23 =G31=0.6*106 lb/in2
The condition of the Geometry and the Boundary
Into a consideration is the cylindrical panel which is the shell with the radius of curvature as 15in
and the length of 14in and the , with nearing to square which covers 55.60 degrees , the arc of
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the cylinder shell. Apart from the radius and the length of the panel, the shell panel has a hole
which is centrally located with a diameter of 2in. the shell panel is created from variety of layers
whose thickness of each is 0.0056in of the material of composite. the below considered specimen
comprises of a fixed bottom having the axial motion only at the top of the edge. The shell panel
is reinforced at the Z axis. This particular analysis is taken in order to get the laminated
composite shell strength which is used in order to form external surface of the aircraft fuselages
and also the motors of the rocket.
A 9 node shell element of the type S9RS is then used together with the mesh which produces 320
elements.
The total number of elements are 320
The number of nodes then is 1344
Through the buckling analysis, this assist the keywords which in this case includes the following;
*shell general section,*Elastic, *Buckle, * Cload which are used to produces the input file ,
which is done by creating a well defined orientation of each and every layer, the materials and
the thickness.
At the beginning, the Boron/Epoxy was engaged then immediately after the analysis, the very 1st
eigenvalue was then engaged direct from the file named the .dat file which was produced.
The very first 1st calculation of the buckling load is done by doing the multiplication of the
applied load which is 1000 in this case by the eigenvalue. The unique words which are used for
the buckling includes the *Buckle and the *Cload. The performance of the glassy/epoxy
analysis, the following were the results which were then obtained.
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The Boron Epoxy
m 1st eigen value 1st buckling load (lb)
1 4.5805 4580.5
2 12.098 12098
3 23.472 23472
4 39.076 39076
5 59.068 59068
The thickness of the shell id then observed direct from the graph of the 1st buckling load versus
the number of thickness for the glassy/epoxy and the Boron/epoxy. This particular curve
indicates progressive increase in the buckling load with respect to increase in the laminate
thickness of the boron/epoxy. The increase is from 4580.5 lb for m=1 to 59068 lb for m=5.
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The Glass/ Epoxy
m 1st eigen value 1st buckling load (lb)
1 1.444 1444
2 3.8848 3884.8
3 7.6618 7661.8
4 12.802 12802
5 19.35 19350
The same to the Boron/epoxy, glass/epoxy has the same progressive increase nature that was
observed with the Boron/Epoxy. The load of the buckling proportionally increases as the
thickness of the material also increases. The loads in this case of glassy/epoxy has a very low
values as compared to the boron/epoxy.
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The buckling load for the boron/epoxy are very much higher as compared to the loads for glass/epoxy
given that the thickness is the same. A good example id the m=3 for the buckle load for boron/epoxy
where lb is 12098 lb and for the glass/epoxy = 3884.8 lb
Conclusion
In conclusion, the 1st buckling load is very higher as the thickness increases. The boron/epoxy is the best
choice for the material since this has very high buckle load as compared to the glass / epoxy when using
the same thickness. In the eve of applying this in the aerospace industry, as the thickness of the material
increases, then the resistance against the buckle with boron/ epoxy becomes more better.
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Appendix
1) Buckle.inp – For boron/epoxy with m=4
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2) Glassbuckle3.inp For glass/epoxy with m=3
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