J. Krystek, R. Kottner, L. Bek

1. Comparison of strength behavior of unidirectional HMC and HSC composite subjected to biaxial loading J. Krystek, R. Kottner, L. Bek 19th 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. 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 Introduction Wrapped pin joint

4. Tensile test Compression test – type I Compression test – type II ( E1, E2, ν12, XT, YT ) ( XC, Y C, α0 ) ( YC, α0 ) ASTM D 3039 ASTM D 3410 Mechanical properties Elasticity and strength parameters of composite

5. Unidirectional composite material Material model Stiffness matrix of transverse isotropic material • 5 independence components of stiffness matrix (C11, C12, C22, C23, C66) • 5 independence material constants(E1, E2, G12 , υ12 , υ13) • Nonlinear function with constant asymptote was used for shear modulus G12: Force and extension dependencies • This material model is not standard part of used FEM system MSC.Marc, therefore it was implemented into MSC.Marc system.

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

7. Experiments • 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 Testing machine Schema of biaxial test

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

9. Specimens • 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 Geometry parameters • Specimens were supplemented with aluminium pads on both sides. • All pads were bonded on the specimens by Araldit AV 138M + HV 998 adhesive Specimens with aluminium pads

10. HSC HMC Experiments - results b = 4.8 mm, h = 2.0 mm b = 5.0 mm, h = 2.2 mm Dependences of specimen strength on the combination of tensile and compression forces Failure of matrix in biaxial test Failure 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

11. FEM system: MSC.Marc • 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 Numerical analysis Modeled quarter Boundary condition

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

13. 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 Summary