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COMPARISON OF FINITE ELEMENT CODES FOR IMPACT SIMULATION ON

COMPOSITES

Jorge Fernando A. Rojas Ulloa.

Supervisor: Jean-Philippe Ponthot.

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CONTENTS

IntroductionObjectivesMethodology

ResultsConclusions

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INTRODUCTION

Composite materials, given their non-homogenousnature, need special laws that describe theirbehaviour.Structures with damage have different propertiesthan non-damaged ones, hence making themdifficult to be studied in a traditional way.

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METHODOLOGY : TEST C ASE DESCRIPTION

Slow velocity impact of a rigid ball against acomposite plate

CompositePlate

Rigid ball

Front view

Top view

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METHODOLOGY : TEST CASE DESCRIPTION

Geometry:

Impactor:A rigid ball, with a radio of 8 [mm].

Composite plate: 12 plies made of a resin HexFlow- RTM6 reinforced with carbonfibers.Stacking sequence S ]0/45[ 3

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METHODOLOGY : M ATERIAL LAWS

Three different material laws were used.Simple orthotropic law: material law 002.

Material law with damage: material law 162.

Cohesive material law: material law 138.

Note: Material law 138 was only used in combination withmaterial law 162.

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METHODOLOGY : M ATERIAL LAW

Definition of different failures modesTension / Shear failure mode.In plane compressive failure mode.Crush failure mode.

In-plane matrix failure mode.Trough the thickness failure mode.

Progressive decrement in the mechanical properties ofthe material.

Can only be integrated using one Gauss point, leading tothe appearance of hourglass modes.

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METHODOLOGY : S IMPLIFICATIONS

Only one quarter of the plate is used due to the symmetryof the problem.The ball is modeled entirely.

Top view

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METHODOLOGY : R UNNING MODEL

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METHODOLOGY : S ENSITIVITY ANALYSIS

Method:Take reference values from literature.Modify value and generate different test-cases.Compare results:

Sensitivity:

* The equation is a numeric approach of a derivate* Cacuci, Dan G., Sensitivity and Uncertainty Analysis:

Theory, Volume I , Chapman & Hall.

|parameteReference parameterVaried|

|result)Reference-resultedmax(Obtain|S

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METHODOLOGY : S ENSITIVITY ANALYSIS

Selected parameters:Other parameters:

PHIC: 10 Coulomb friction angle.S_DELM: 1.2 Scale factor of the delamination area.

SFS : 0.3 Fiber mode shear strength.SFFC: 0.3 Scale factor for compressive strength.SFC: 0.850 Crush strength.

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RESULTS

The results obtained for all the parameters areshown:

Parameter Sensitivity Range AM1 / AM2 0.709 [1 - 3]

AM3 0.473 [0.2 1.0]AM4 2.112 [0.001 0.5]

E_LIMIT 1.254 [0.01 0.2]ECRSH 50.25 [0.001 0.05]EEXPN 0.164 [3 - 5]

CERATE1 1.620 [0.01 0.2]

CERATE2 3.123 [0.001

0.1]CERATE3 3.787 [-0.01 0.1]CERATE4 5.290 [0.001 0.1]

PHIC 0.083 [10 - 40]

S_DELM 0.145 [0.4 2.0]SFS 2.474 [0.1 0.5] [GPa]

SFFC 2.112 [0.1 0.5]SFC 1.366 [0.650 1.050] [GPa]

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CONCLUSIONS

It is mandatory to define an hourglass control. Ifnot, the model will be no valid.

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CONCLUSIONS

Mesh convergence.

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CONCLUSIONS

The obtained sensitivity values need to be takenglobally.

It is necessary to understand what means eachparameter.Select a correct range for the parameter.

The low velocity impact is not the best referencetest to implement to law to perform an sensitivityanalysis.The recommended test is a quasi-static punch-shear loading test of the material.

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THANKS FOR YOUR ATTENTION .

Questions?