Machining of Composite Materials

Machining of Composite Materials:

Machining of Composite Materials 1 Krishna K. Krishnan, Professor Department of Industrial & Manufacturing Engineering Behnam Bahr, Professor Department of Mechanical and Aerospace Engineering California State University ADMRC

Industrial Contacts :

Industrial Contacts Spirit AeroSystems Mr. John Boccia Mr. Dan Thurnau Hawker Beechcraft Mr. Phil Douglas Cessna Mr. Dhananjay Joshi Mr. Erkan Kececi Mr. Shannon Jones 2

OBJECTIVE:

OBJECTIVE To develop optimal machining of composites using experimental and theoretical models with the aim of improving surface finish and minimizing cutting forces and delamination To establish criteria for cutting tool selection and machining parameters such as feed and speed to cost effectively improve machining process 3

VARIABLES AFFECTING THE MACHINING QUALITY:

VARIABLES AFFECTING THE MACHINING QUALITY 4

Nomenclature:

Nomenclature 5 matrix cross-sectional area associated with one fiber fiber spacing Young’s modulus of fiber thickness of workpiece Young’s modulus of matrix length effective Young modulus number of representative volume elements effective modulus of workpiece material in Region 3 fiber radius total cutting force total thrust force Tool tip radius cutting force associated with fiber microbuckling lateral force at the fiber free end portion of thrust force associated with fiber microbuckling critical lateral force associated with fiber bending cutting force associated with fiber bending and matrix shearing critical lateral force associated with matrix shearing friction on the tool rake face fiber deflection shear forces acting on the shear plane fiber volume fraction normal force acting on the shear plane relief angle machining forces friction angle shear modulus of matrix rake angle in orthogonal cutting tool shear modulus of a circular fiber-reinforced composite shear strain in the matrix material second moment of area of the cross section of the fiber friction coefficient Coefficient minor Poisson’s ratio reinforcement length composite critical stress for the fiber bending failure mode indentation force real resultant force composite critical stress for the matrix shear failure mode total energy in a single fiber and surrounding matrix material , shear strengths of workpiece flexure strength of fiber shear strength of matrix feed rate (undeformed chip thickness) shear stress in the matrix material chip thickness fracture plane angle width of contact matrix cross-sectional area associated with one fiber fiber spacing Young’s modulus of fiber thickness of workpiece Young’s modulus of matrix length effective Young modulus number of representative volume elements effective modulus of workpiece material in Region 3 fiber radius total cutting force total thrust force Tool tip radius cutting force associated with fiber microbuckling lateral force at the fiber free end portion of thrust force associated with fiber microbuckling critical lateral force associated with fiber bending cutting force associated with fiber bending and matrix shearing critical lateral force associated with matrix shearing friction on the tool rake face fiber deflection shear forces acting on the shear plane fiber volume fraction normal force acting on the shear plane relief angle machining forces friction angle shear modulus of matrix rake angle in orthogonal cutting tool shear modulus of a circular fiber-reinforced composite shear strain in the matrix material second moment of area of the cross section of the fiber friction coefficient Coefficient minor Poisson’s ratio reinforcement length composite critical stress for the fiber bending failure mode indentation force real resultant force composite critical stress for the matrix shear failure mode total energy in a single fiber and surrounding matrix material shear strengths of workpiece flexure strength of fiber shear strength of matrix feed rate (undeformed chip thickness) shear stress in the matrix material chip thickness fracture plane angle width of contact

ORTHOGONAL CUTTING:

ORTHOGONAL CUTTING 6

EXPERIMENTAL CUTTING PROCESS:

EXPERIMENTAL CUTTING PROCESS 7

FIBER ORIENTATION CLASSIFICATION:

FIBER ORIENTATION CLASSIFICATION 8

EXPERIMENT TO THEORY:

EXPERIMENT TO THEORY 9

EFFECT OF FIBER ORIENTATION IN CUTTING MECHANISMS:

10 EFFECT OF FIBER ORIENTATION IN CUTTING MECHANISMS Year one (2009): Year two (2010): Chipping Pressing Bouncing

Slide 11:

11 EFFECT OF TOOL RAKE ANGLE AND FIBER ORIENTATION (ORTHOGONAL CUTTING-NEWPORT) Rake=5 Rake=10 Rake=15

Slide 12:

12 EFFECT OF TOOL RAKE ANGLE AND FIBER ORIENTATION (ORTHOGONAL CUTTING-NEWPORT ) Rake=5 Rake=10 Rake=15

Slide 13:

13 Rake=5 Rake=10 Rake=15 EFFECT OF TOOL RAKE ANGLE AND FIBER ORIENTATION (ORTHOGONAL CUTTING-CESSNA)

Slide 14:

14 EFFECT OF TOOL RAKE ANGLE AND FIBER ORIENTATION (ORTHOGONAL CUTTING-CESSNA ) Rake=5 Rake=10 Rake=15

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COMPARISON BETWEEN FEM AND EXPERIMENTS 15 Broken fibers

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16 COMPARISON BETWEEN FEM AND EXPERIMENTS

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17 COMPARISON BETWEEN FEM AND EXPERIMENTS Severe fiber and matrix damage

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18 COMPARISON BETWEEN FEM AND EXPERIMENTS Severe fiber and matrix damage

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19 FINITE ELEMENT ANALYSIS

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20 FINITE ELEMENT ANALYSIS

EFFECT OF TOOL NOSE RADIUS ON CUTTING MECHANISM:

21 EFFECT OF TOOL NOSE RADIUS ON CUTTING MECHANISM

ACTUAL COMPOSITE MODEL WITH ROUND FIBERS:

22 ACTUAL COMPOSITE MODEL WITH ROUND FIBERS

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ORTHOGONAL CUTTING Cutting Force Comparison (FEM vs. Experiment) 23

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ORTHOGONAL CUTTING Thrust Force Comparison (FEM vs. Experiment) 24

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ORTHOGONAL CUTTING FIBER ORIENTATION 25

Slide 26:

26

Slide 27:

27 SIMPLE INTERFACE

Slide 28:

28 MATERIAL PROPERTIES USED FOR ANALYTICAL AND FEM ANALYSIS

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THEORY AND EXPERIMENT COMPARISON (DEPTH OF CUT = , RAKE ANGLE = , RELIEF ANGLE = ) 29

Slide 30:

30

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ORTHOGONAL CUTTING FIBER ORIENTATION (Chipping) 31

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ORTHOGONAL CUTTING FIBER ORIENTATION (Pressing) 32 Where

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ORTHOGONAL CUTTING FIBER ORIENTATION (Bouncing) 33 Where

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ORTHOGONAL CUTTING FIBER ORIENTATION (Total) 34 Total Cutting Force = + + 

OBLIQUE CUTTING:

OBLIQUE CUTTING 35

OBLIQUE CUTTING TOOL:

OBLIQUE CUTTING TOOL 36

PREDICTION OF DAMAGE LENGTH (OBLIQUE CUTTING):

PREDICTION OF DAMAGE LENGTH (OBLIQUE CUTTING) 37 The theory shows Helix Angle does not have a significant effect on in-plane damage

Slide 38:

38 EFFECT OF TOOL RAKE ANGLE AND FIBER ORIENTATION (OBLIQUE CUTTING-CESSNA ) Rake=5 Rake=10 Rake=15 : Fiber Orientation : Tool Inclination Angle Higher inclination angle results in more out of plane deformation of fibers

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OBLIQUE CUTTING - - 39

MACHINING CONDITIONS:

MACHINING CONDITIONS Hawker Speed 2500 rpm 3500 rpm 5000 Feed 10 ipm 14 ipm 20 ipm Cessna Speed 12000 rpm 18000 rpm 24000 rpm Feed 50 ipm 70 ipm 100 ipm 40

EXPERIMENTS:

EXPERIMENTS 41

Slide 42:

42 Cessna Material “Unidirectional and all layers in the same direction”

Slide 43:

43 EXPERIMENTAL RESULTS Speed: 5000 rpm– Feed: 20 ipm

HIGH RPM MACHINING:

HIGH RPM MACHINING 44

SPEED:24000 (rpm) – FEED: 100 (ipm):

SPEED:24000 (rpm) – FEED: 100 ( ipm ) 45

EFFECT OF MACHINING SPEED ON DAMAGE (Linear strain rate behavior):

46 EFFECT OF MACHINING SPEED ON DAMAGE (Linear strain rate behavior)

Slide 47:

47 Wear-out Tests Spirit Materials and Router

Slide 48:

48 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials Tool Wear-out

Slide 49:

49 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials Tool Microscopic Images

Slide 50:

50 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials Surface Finish – Top

Slide 51:

51 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials Surface Finish – Bottom

Slide 52:

52 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials Cutting Zone Temperature

Slide 53:

53 EXPERIMENTAL RESULTS Wear-out Tests on Spirit Materials (Speed: 3000 RPM – Feed: 42 IPM – Conventional Cutting)

DRILLING OF COMPOSITES:

DRILLING OF COMPOSITES 54

Slide 55:

55 DRILLING AND OBLIQUE CUTTING

CONCLUSIONS:

CONCLUSIONS Higher RPMs reduce the cutting damage due to increased matrix strength. Oblique cutting experiments with single edge cutting tool results in more out of plane fiber deformation. T hree dimensional FEM models of orthogonal and oblique cutting were developed and cutting mechanisms were investigated. Theoretical models for orthogonal cutting forces was developed for as well as The effect of tool nose radius was investigated using FEM. Tool Wear-out experiments were conducted on the Spirit materials with the provided routers and critical wear-out measures were reported.

Slide 57:

Thank You !