1. UNIVERSITY OF THE BASQUE COUNTRY
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
UNIVERSITY OF THE BASQUE COUNTRY
DETERMINATION OF TRANSVERSE COMPRESSIVE STRENGTH OF LONG FIBER COMPOSITES BY THREE-POINT BENDING OF [90m/0n] LAMINATED STRIPS
N.Carbajal, A. Arrese, G. Vargas, F. Mujika
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

2. 3. OPTIMAL CONFIGURATION 4. EXPERIMENTAL 5. RESULTS AND DISCUSSION
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
OUTLINE
1. INTRODUCTION
2. ANALYTICAL APPROACH
3. OPTIMAL CONFIGURATION
4. EXPERIMENTAL
5. RESULTS AND DISCUSSION
6. CONCLUSSIONS
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

3. determining transverse compressive strength.
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
1. INTRODUCTION
• Three-point bending tests of cross-ply laminate strips are proposed for
determining transverse compressive strength.
• Stress state has been obtained based on the hypothesis of the Classical
Beam Theory (CBT)
• An adequate configuration has been obtained by imposing the condition
of maximum ratio between compressive stresses at 90º layer and tensile
stresses at 0º layers.
• Three-point bending tests with different thicknesses and spans have
been carried out.
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

4. 2. ANALYTICAL APPROACH MAIN HIPOTHESES
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
2. ANALYTICAL APPROACH
MAIN HIPOTHESES
• Longitudinal strain on x axis ex is a linear function of z,
where the reference of z coordinate is at the midplane.
• The only non vanishing stress components in each ply are sx and ts.
• Each ply is linearly elastic.
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

5. STRESS-STRAIN RELATIONS AT A LAYER FORCES AND MOMENTS PER UNIT LENGTH
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRESS-STRAIN RELATIONS AT A LAYER
FORCES AND MOMENTS PER UNIT LENGTH
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

6. STRAINS AND CURVATURES OF MIDPLANE
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRAINS AND CURVATURES OF MIDPLANE
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

7. OPTIMAL THICKNESS RATIO
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRESS RATIO
OPTIMAL THICKNESS RATIO
MAXIMUM STRESS RATIO
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

8. STRESS RATIO, THICKNESS RATIO AND MODULUS RATIO
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRESS RATIO, THICKNESS RATIO AND MODULUS RATIO
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

9. 3. OPTIMAL CONFIGURATION CONDITIONS IMPOSED FOR OPTIMAL CONFIGURATION
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5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
3. OPTIMAL CONFIGURATION
CONDITIONS IMPOSED FOR OPTIMAL CONFIGURATION
• Neutral axis has to be located as close as possible to the bottom
part of 90º layer in order to avoid tensile stresses at 90º layer.
• Maximum thermal stresses must be lower than transverse strength in order to avoid premature failures in 90º layer.
• Maximum tensile stresses at 0º layer must be lower than tensile strength.
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

10. OPTIMAL CONFIGURATION FOR T6T-F593 -> [904n/0n]
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
OPTIMAL CONFIGURATION FOR T6T-F593 -> [904n/0n]
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

11. MAXIMUM TRANSVERSE COMPRESSIVE STRESS
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
MAXIMUM TRANSVERSE COMPRESSIVE STRESS
TRANSVERSE COMPRESSIVE STRENGTH FOR T6T-F593
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

12. 4. EXPERIMENTAL THREE-POINT BENDING T6T-F593 CARBON/EPOXY SAMPLES
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
4. EXPERIMENTAL
THREE-POINT BENDING
MTS electromechanical machine
Roller radius = 2.5 mm
T6T-F593 CARBON/EPOXY
SAMPLES
Sample
h (mm)
hT (mm)
hL (mm)
[909/03]-30
[9016/04]-30
[9020/05]-40
2.07
2.97
3.90
1.55
2.38
3.12
0.52
0.59
0.78
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

13. 5. RESULTS AND DISCUSSION
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
5. RESULTS AND DISCUSSION
STRESS PROFILES [909/03]- 30
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

14. OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRESS PROFILES [9016/04]- 30
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

15. OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
STRESS PROFILES [9020/05]- 40
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

16. OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
PHOTOS OF FAILURE
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

17. LOAD UNLOAD CYCLES PRIOR TO FAILURE
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
LOAD UNLOAD CYCLES PRIOR TO FAILURE
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

18. strength by three-point bending only depends on the relation
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
6. CONCLUSIONS
• Optimal cross-ply configuration for determining transverse compressive
strength by three-point bending only depends on the relation
between transverse and longitudinal modulus.
• For optimal configuration of a given material the ratio between maximum
stresses at 90º and 0º layers are maximum and only depends on
the relation between transverse and longitudinal modulus.
• Transverse compressive strength values are very similar between them.
• The appearance of damage agrees well with the transverse compressive
failure related to end-loaded compression tests.
• No tensile failure has been found prior to final failure.
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips

19. THANK YOU FOR YOUR ATTENTION
OFF-AXIS FLEXURE
5th International Conference on Composites Testing and Model Simulation
EPFL, Lausanne, 2011
THANK YOU FOR YOUR ATTENTION
Determination of transverse compressive strength of long fiber composites by three-point bending of [90m/0n] laminated strips