machining of composite materials - iit kanpurmachining of composite materials j.ramkumar ......

Machining of composite Materials

J.Ramkumar

Micromanufacturing lab

Dept of Mechanical Engineering

IIT Kanpur

[email protected]

Mechanics of Reinforced Polymer Composites

Introduction • Composite materials have higher specific properties

• Good corrosive resistance

• Good fatigue resistance

• Selective properties

• Economic for small batch sizes

However because of

• Non homogeneous

• Anisotropic

• Reinforced properties

Difficult to machine – Abrasive chip leading to tool wear, workpiecedamage


Classification: Particle-Reinforced (i)

• Examples:Adapted from Fig. 10.19,

Callister & Rethwisch 8e.

(Fig. 10.19 is copyright

United States Steel

Corporation, 1971.)

- Spheroidite

steel

matrix: ferrite (a)

(ductile)

particles: cementite(Fe

3C )

(brittle)60 mm

Adapted from Fig. 16.4,


(Fig. 16.4 is courtesy

Carboloy Systems,

Department, General

Electric Company.)

- WC/Co

cemented

carbide

matrix: cobalt (ductile,

tough)

particles: WC (brittle, hard):

600mm



(Fig. 16.5 is courtesy

Goodyear Tire and Rubber

Company.)

- Automobile

tire rubber

matrix: rubber (compliant)

particles: carbon

black

(stiff) 0.75mm

Particle-reinforced Fiber-reinforced Structural

• Aligned Continuous fibers• Examples:

From W. Funk and E. Blank, “Creep deformation of

Ni3Al-Mo in-situ composites", Metall. Trans. A Vol.

19(4), pp. 987-998, 1988. Used with permission.

-- Metal: g'(Ni3Al)-a(Mo)by eutectic solidification.

Classification: Fiber-Reinforced (iii)


matrix: a (Mo) (ductile)

fibers: g ’ (Ni3Al) (brittle)

2mm

-- Ceramic: Glass w/SiC fibersformed by glass slurry

Eglass = 76 GPa; ESiC = 400 GPa.

(a)

(b)

fracture surface

From F.L. Matthews and R.L. Rawlings,

Composite Materials; Engineering and

Science, Reprint ed., CRC Press, Boca

Raton, FL, 2000. (a) Fig. 4.22, p. 145 (photo

by J. Davies); (b) Fig. 11.20, p. 349

(micrograph by H.S. Kim, P.S. Rodgers, and

R.D. Rawlings). Used with permission of

CRC

Press, Boca Raton, FL.

• Laminates -

-- stacked and bonded fiber-reinforced sheets

- stacking sequence: e.g., 0º/90º

- benefit: balanced in-plane stiffnessAdapted from Fig.

16.16, Callister &

Rethwisch 8e.

Classification: Structural


• Sandwich panels-- honeycomb core between two facing sheets

- benefits: low density, large bending stiffness

honeycomb

adhesive layerface sheet



(Fig. 16.18 is from Engineered Materials

Handbook, Vol. 1, Composites, ASM International, Materials Park, OH, 1987.)

Choosing a process

• Reinforcement in composites – glass, graphite, boron, alumina and SiC – abrasive in nature and hard

• Majority of the machining happens to brittle fracture rather than plastic deformation ahead of tool.

• Depends on matrix property too

• Volume fraction plays an important role

• Part size and shape

• Number


Role of matrix and reinforcement

• To protect the reinforcement materials

• To distribute the stress to the reinforcement materials

• To provide for the final shape of the composite part

Reinforcement

• To provide the composite high Mechanical properties

• To reinforce the matrix in preferential direction


a b

Evolution of matrix damage:(a) crushing and (b) cracking during chip formation.

Comparison between CFRP and GFRP.

Cutting tool spectrum


Vibratory assisted turning


Tool wear profile


Effect of vibration

• For fibre orientation0o, in conventionalcutting lots of fibresare pulled out (1.a). Inultrasonic vibrationcutting, those fibresare absent (1.b).

• for fibre orientation90o, in conventionalcutting fibres are notcut at the edge of thesurface (2.a). Inultrasonic vibrationcutting, however,those fibres are notvisible (2.b

1.

2.

Schematic diagram of experimental setup


Typical forces during drilling


Thrust and torque over drilling cycle


Delamination mechanism


Hole quality assessment


Delamination measurement techniques


Varying drill geometry


Vibration assisted drilling


Advantage of vibration assisted drilling


(III) Milling of FRP

Experimental setup for FRP milling

Contact and rubbing actions between the fibres and each cutting flutes as the tool rotates and cuts across the fibres(at centre position of the cutting flutes)

Milling is used, as a corrective end machining operation or to produce defined,high quality surfaces. The fibre type, reinforcement architecture and matrixvolume fraction are the most important factors governing tool selection andmachining parameter setting.

In the case of glass and carbon fibrereinforcement, it is the cutting toolmaterial, that dominates the toolselection

Quality achieved when milling thermoplastic matrix GFRP composite laminates

Surface roughness in milling of GFRP composites

Some experientialresults on surfacequality, when millingof FRP wereperformed as shown.

Laser drilling composites


Processing materials by mixing fire and water


Water jet cutting of composites


Schematic diagram


Water jet machining evaluation


Typical AWJ cut kerf geometry: (a) end view of kerf, and (b) kerf wall roughness

a b

Machining of PMC by AWJM

AWJ set up

Traverse speed vs. kerf width and taper

Traverse speed vs. kerf wall surface roughness

Traverse speed are the superioroperating parameters for affectingthe surface roughness and kerftaper angle. With an increase intraverse speed bad surface finishand high kerf taper angle obtained

Water Jet Milling


Conclusions

• An overview of various issues in machining of composites materials are discussed

• Latest research areas in machining of composites are covered

• Composites machining is always a challenging problem from engineers.


machining of composite materials - iit kanpurmachining of composite materials j.ramkumar ......

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