1. By Prof. M. ELMESSIRY Textile Eng. Department Alexandria university
FACTORS AFFECTING THE MODEL OF FAILURE OF 3-D BRAIDED COMPONENTS UNDER TORSIONAL STRESS By
Prof. M. ELMESSIRY
Textile Eng. Department
Alexandria university

2. INTRODUCTION
Several types of composite materials are widely used at the present time
Several methods of fiber architecture are used
2-D and 3-D weave, 3-D braiding

3. 3-D weave 3-D braiding are claimed to prevent the lamination

4. GRAPHITE COMPOSITES ARE IDEALLY SUITABLE FOR APPLICATION WHERE HIGH STIFFNESS, LOW COEFFICIENT OF THERMAL EXPANSION AND LOW WEIGHT ARE REQUIRED

5. APPLICATION IN
SPACE CRAFT STRUCTURE
AIRCRAFT
DRIVE SHAFT

6. Composite material applications

13. EWAYNE
SHOWED THAT THE APPLICATION OF THE COMPOSITES TO ROBOTICS AND AUTOMATION INDUSTRY GIVES SEVERAL BENEFITS;
LIGHT WEIGHT
HIGH STIFFNESS
HIGH STRENGTH
EXTENDED LIFE CYCLE
IMPROVE VIBRATION DAMPING

14. JAMES ANALYSED THE DESIGN OF WIND TURBINE COMPOSITE BLADES
TORSION REGIDITY OF THE BLADE CONSIDERED TO BE THE MOST IMPORTANT FACTOR IN THE BLADE DESIGN

15. KO
DEVELOPED THE 3-D BRAIDED STRUCTURE GEOMETRY TO DEFINE THE ORIENTATION OF THE FIBERS AND THE FIBER VOLUME FRACTION

16. FABRIC GEOMETRY MODEL

17. SCHEMATIC DRAWING OF ONE REPEAT OF 4-STEP STRUCTURE

18. OBJECTIVES OF THE PRESENT WORK
INVESTIGATE THE TORSIONAL BEHAVIOR OF COMPOSITE MATERIAL BEAMS STRENGTHEN WITH 4-STEP BRAIDED GRAPHITE FIBERS
IDENTIFY THE INFLUENCE OF THE BRAID PITCH ON BOTH TORSION AND RELAXATION BEHAVIOR

19. EXPERIMENTAL TEST SPECIMEN SPECIFICATIONS
4-STEP 3-D BRAIDED SPECIMENS OF PITCH LENGTHS:
7 MM
12 MM
14 MM

20. 12 K GRAPHITE FIBER
EPOXY RESIN EPON 828
SPECIMEN SIZE: 150X19 MM
SPECIMEN THICKNESS: 3 MM

21. TORSION SET-UP DESIGN
SPECIAL SET-UP WAS DEVELOPED TO APLLY THE TORQUE ON THE SPECIMEN WHICH WAS FIXED IN THE JAWS THAT ALLOWED THE SPECIMEN ENDS FREELY SLIDE DURING THE APPICATION OF THE TORQUE
BOTH APPLIED TORQUE AND TWIST ANGLE WAS MEASURED

22. RESULTS AND DISCUSSION
RELATION BETWEEN THE APPLIED TWISTING TORQUE AND THE TWISTED ANGLE PER METER FOR THE DIFFERENT SPECIMENS WAS MEASURED

24. FROM THE ANALYSIS OF THE CURVES IT IS CLEAR THAT:
ALL THE SPECIMENS HAVE A LINEAR RELATION BETWEEN TORQUE AND TWISTING ANGLE
YIELD STARTED TO APPEAR AT A CERTAIN VALUE OF TWISTING ANGLE

25. The value of the pitch length affects:
yielding torque
yield twisting angle
torsion stiffness

26. VALUE OF THE YEILD TORQUE INCREASES WITH THE INCREASE OF THE PITCH LENGTH
VALUE OF THE YEILD ANGLE ALSO INCREASES WITH THE INCREASE OF THE PITCH LENGTH

27. EFFECT OF THE PITCH LENGTH ON THE YIELD TORQUE AND YIELD TWISTING ANGLE
AS THE PITCH LENGTH INCREASES THE COMPOSITE MATERIAL HAS A HIGER VALUE OF FIBER VOLUME FRACTION

28. Relative Shear Modules

30. MODEL OF THE DEFORMATION OF THE COMPOSITE MATERIAL UNDER TORSION LOAD
BRAIDED COMPOSITE MATERIAL HAS THREE DIFFERENT LAYERS:
SURFACE RESINE ZONE
FIBER BRAIDED STRUCTURE ZONE
ZONE BETWEEN FIBERS

31. SHEAR VALUE ON THE CROSS-SECTION OF THE SPECIMEN SHOWS IT’S MAXIMUM VALUE AT THE SURFACE
UNDER THE TWISTING TORQUE THE SURFACE FIBERS WILL MOVE OUT APPLYING ADDITIONAL SHEAR STRESS ON THE SURFACE LAYER OF THE RESIN

32. CAUSE A LAMINATION OF THE RESIN TRYING TO SPLIT THE SURFACE OF THE SPECIMEN
CAUSE CRACKS OF THE SIZE PROPOTIONAL TO THE PITCH LENGTH WHICH PROPAGATE OVER THE TOW KNEE DIRECTION
SPECIMEN WILL YIELD UNDER THE TORQUE APLIED

33. RELAXATION OF COMPOSITE MATERIAL
VALUE OF THE INSTANT RELAXATION IS FUNCTION OF THE PITCH LENGTH
AS THE FIBER VOLUME FRACTION INCREASES
VALUE OF THE INSTANT RECOVERY DECREASES

34. . CLOSE STRUCTURE OF THE BRAIDED PERFORM DELAYS THE RECOVERY OF THE SPECIMEN AFTER THE REMOVAL OF THE TORQUE
MAXWELL AND KELVIN MODELS WERE INVESTIGATED TO DESCRIBE THE STRESS RELAXATION RELATION

35. MAXWELL MODEL

36. KELVIN MODEL

37. ZENER MODEL

38. IMPROVED ZENER MODEL

39. IT IS SUGGESTED TO USE A MODIFIED MODEL OF “n” MAXWELL ELEMENTS IN PARALLEL WITH THE ELASTIC SPRING
“IMPROVED ZENER MODEL” MAY EXPLAIN BETTER RELAXATION OF THE COMPOSITE MATERIAL FORMED BY 4-STEP 3-D BRAIDED SPECIMENS
VALUE OF “n” IS A FUNCTION OF THE PITCH LENGTH
SMALLER PITCH VALUE GREATER NUMBER OF MAXWELL ELEMENT IN THE MODEL

40. CONCLUSION
IN THIS WORK THE EFFECT OF THE PITCH LENGTH ON THE TORSION REGIDITY AND RELAXATION OF 4-STEP 3-D BRAIDED GRAPHITE COMPOSITE WAS EXPERIMENTALLY INVESTIGATED
THE RESULTS SHOW THAT:
PITCH LENGTH CHANGES THE TORSION REGIDITY
BEHAVIOR OF THE FRACTURE UNDER THE TORSION STRESS DEPENDS ON THE PITCH LENGTH
VALUE OF THE INSTANT RECOVERY INCREASES WITH THE INCREASE OF THE PITCH LENGTH

41. END