1. Comparison of strength behavior of unidirectional HMC and HSC composite subjected to biaxial loading J. Krystek, R. Kottner, L. Bek 19 th Conference on Materials and Technology; 22 and 23 November 2011, Portorož, Slovenia

2. Outline Introduction Material model Mechanical properties Failure criteria Experiments Numerical analysis Summary

3. Introduction –Currently, the failure of composite is well predictable only in basic cases –Biaxial tests shown dependence of specimen strength on the ratio of tension and compression Wrapped pin joint

4. Mechanical properties Tensile test Type of fibers [GPa] [ - ][GPa] [ - ][MPa] [ ° ] HSC120.08.00.3374.8110.01.111800850552138259 HMC200.06.80.2906.5128.01.281770685421606057 Elasticity and strength parameters of composite Compression test – type ICompression test – type II ( E 1, E 2, ν 12, X T, Y T ) ( Y C, α 0 ) ( X C, Y C, α 0 ) ASTM D 3410 ASTM D 3039

5. Material model o Unidirectional composite material Stiffness matrix of transverse isotropic material –5 independence components of stiffness matrix ( C 11, C 12, C 22, C 23, C 66 ) –5 independence material constants ( E 1, E 2, G 12, υ 12, υ 13 ) –Nonlinear function with constant asymptote was used for shear modulus G 12 : – This material model is not standard part of used FEM system MSC.Marc, therefore it was implemented into MSC.Marc system. Force and extension dependencies

6. Failure criteria o FIBRE FAILURE o MATRIX FAILURE –Maximum stress –Hashin –LaRC04 #3 –adjusted LaRC04 #3 –Maximum stress –Hashin –LaRC04 #2 –adjusted LaRC04 #2

7. Schema of biaxial test Testing machine –Biaxial test –Standard testing machine Zwick/Roell Z050 was supplemented by second loading axis for the localized compression –The second loading axis consisted of power machine vice VMC-130 and HBM C9B compact force transducer Experiments

8. –Loading was applied in two basic steps Loading steps

9. –Specimens were cut using water jet from unidirectional composite plates, which were made from 8 layers of prepreg –Geometry parameters of specimens  HSC composite b = 5.0 mm, h = 2.2 mm, l = 240 mm  HMC composite b = 4.8 mm, h = 2.0 mm, l = 240 mm –Geometry parameters of compression element: w = 20 mm, v = 10 mm, R = 1 mm –Specimens were supplemented with aluminium pads on both sides. –All pads were bonded on the specimens by Araldit AV 138M + HV 998 adhesive Geometry parameters Specimens with aluminium pads Specimens

10. Experiments - results Dependences of specimen strength on the combination of tensile and compression forces HSCHMC Failure of matrix in biaxial testFailure of fibres in biaxial test –Compressive strength (matrix failure) is increasing with the tensile force –Tensile strength (fibre failure) is decreasing with the compressive loading b = 5.0 mm, h = 2.2 mm b = 4.8 mm, h = 2.0 mm

11. Numerical analysis o FEM system: MSC.Marc Boundary condition –Regarding symmetry of the specimen, only one quarter of the specimen was modelled –Loading was applied in two basic steps which correspond with experiment –Compressive loading was applied by force acting on contact surface which represented compressive element –Friction was neglected Modeled quarter

12. Numerical analysis Failure index for Hashin - fibre failure Failure index for LaRC04 #2 - matrix failure Failure index for Maximum stress - matrix failure o HSC composite

13. Summary –Selected stiffness and strength parameters of composites were identified –Composites had high modulus carbon (HMC) fibres and high strength carbon (HSC) fibres –Strength analysis of the composites subjected to biaxial loading was performed –Experimental specimens were loaded in two perpendicular directions –Specimens were exposed to the combination of the tension in the fibre direction and the localized compression in the transverse direction –Loading was applied in two basic steps –Experiments showed similar dependence of specimen strength of both types of composite on the ratio of tension and compression –Compressive strength is increasing with the tensile force –Tensile strength is decreasing with the compressive force –Predictive capabilities of different failure criteria for composite materials were tested in the failure analysis - Maximum stress, Hashin, LaRC04