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School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Testing and Modeling Rate Dependent Properties of Polymeric Composites Using Off-axis.

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Presentation on theme: "School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Testing and Modeling Rate Dependent Properties of Polymeric Composites Using Off-axis."— Presentation transcript:

1 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Testing and Modeling Rate Dependent Properties of Polymeric Composites Using Off-axis Specimens C.T. Sun School of Aeronautics and Astronautics Purdue University West Lafayette, Indiana USA CompTest January 2003 Chalons en Champagne

2 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Off-Axis Composite Under Uniaxial Load a state of combined stress

3 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Objectives Nonlinear constitutive model for UD composites Rate dependent behavior Compressive strength –static and dynamic

4 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Off-Axis Testing Anisotropic Nonlinear Off-Axis Stress-Strain Curves Unidirectional S2Glass/8553 Nonlinear Behavior in Fiber Composites

5 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Plastic Potential and Flow Rule Flow RuleOne-Parameter Plastic Potential No plastic strain in the fiber direction Satisfies transverse isotropy Transversely isotropic

6 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Off-Axis Test-Plane Stress Power Law

7 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Master Curve in Effective Stress and Effective Plastic Strain a 66 is determined by collapsing the off-axis curves into a master curve

8 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Effective stress Effective plastic strain rate Viscoplasticity model NONLINEAR RATE DEPENDENT CONSTITUTIVE MODEL

9 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun NONLINEAR RATE DEPENDENT CONSITUTIVE MODEL-Continued Off-axis test results  = /S. a 66 = 6

10 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun n=5.2 NONLINEAR RATE DEPENDENT CONSITUTIVE MODEL-Continued A=2.8E-16 A=1.0E-16 A=4.0E-17

11 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun NONLINEAR RATE DEPENDENT CONSITUTIVE MODEL-Continued

12 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Specimen Hard steel  x Y 10 mm 6 mm Applied displacement Strain gage Dynamic COMPRESSION TEST Compression tests were performed on 5° and 10° off-axis S2/8552 glass/epoxy composites at strain rates from /s to 1000/s. Quasi-Static

13 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun SPLIT HOPKINSON BAR TEST AS4/ degree unlapped and unlubricated

14 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun SPLIT HOPKINSON BAR TEST- Continued Lapped and lubricated AS4/3501-6S2/ degree

15 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun VERIFICATION OF CONSTITUTIVE MODEL

16 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun COMPRESSIVE FAILURE MODELS Shear modeExtension mode 12 Shear mode Rosen (1965): Idealize the composite as a series of perfectly aligned beam embedded in elastic matrix. Two modes of failure: extension and shear.

17 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Compressive Failure Kink Band

18 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun xx xx Argon(1972) a kinking failure mechanism due to fiber misalignment and composite shear yielding. COMPRESSIVE FAILURE MODELS

19 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Budiansky (1983) Budiansky and Fleck (1993) COMPRESSIVE FAILURE MODELS

20 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Sun and Jun (1994) Fiber microbuckling in nonlinear matrix including fiber misalignment effect  ff mm mm COMPRESSIVE FAILURE MODELS

21 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Microbuckling Model PP Need a nonlinear rate dependent constitutive model Elastic Viscoplastic

22 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun DYNAMIC MICROBUCKLING MODEL

23 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun For off-axis composites TANGENT SHEAR MODULUS G 12 ep  1         12 G 

24 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun SIMPLIFIED MODEL For small value of  sin  0 Further simplification ~ ~

25 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun EXAS HIS/DX6002 Carbon/epoxy composites*,v f =65% Fiber misalignment = 2 o EFFECT OF SHEAR STRESS

26 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun EXPERIMENTAL RESULTS AND MODEL PREDICTION- MICROBUCKLING

27 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun

28 School of Aeronautics and Astronautics, Purdue UniversityC.T. Sun Conclusions The use of off-axis composite specimens to establish rate dependent nonlinear constitutive models is convenient. The microbuckling model together with the rate dependent nonlinear constitutive model can predict the static and dynamic compressive failure of UD composites.


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