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Fabrication of composite leaf spring
- 1. Fabrication of CompositeLeaf Spring -By Pratik Shriraj Gandhi T.Y.B.Tech Production (Sandwich) 111213021
- 2. 1. Introduction •Suspension • Conservation of natural resources and economize energy, weight reduction • Load carrying capacity • Steel springs makes vehicles heavy • Key factors in selecting material- shock absorbing & load
- 3. • Functions -locating points of stress, damping vibrations and springing • Absorb & store energy • Specific strain energy - • Weight reduction with equal stability, high specific strength & high specific Modulus • Alternative - Glass Fiber Reinforced Plastic (GFRP) • Problems faced - weight increase, low performance, excess wear • Composites - lightweight, strong, high strength to weight ratio
- 4. 2. Conventional LeafSprings • Absorbs sudden load and fluctuations • Accumulates elastic energy • Provide suspension for chassis of vehicle
- 5. 2.1. Working ofLeaf Springs • Semi-elliptic leaf springs • Blades vary in length, given initial curvature or cambered tend to straighten under load • Lengthiest blade - Master leaf • Other blades - Graduated leaves • Front end connected with pin joint, rear end with shackle • Vehicle across projection on road, wheel moves up, deflecting the spring which changes the length between the spring eyes
- 6. 2.2. Types Leafsprings Multi-Leaf Spring Mono Leaf Spring Parabolic Single Leaf Spring Fiberglass Leaf Spring •more than 1 leaf •assembled using center bolt and clips •only 1 leaf •constant width and thickness •lighter spring rate •one main leaf with tapered thickness •lighter than multi-leaf springs •made of a mixture of plastic fibers and resin •sensitive to heat •lighter than all other springs but cost is three times greater
- 7. 3.Design Parameters •Material selected • Tensile strength • Yield strength • Young’s modulus E • Design stress (σb) • Total length • Spring weight • Arc length between axle seat and Front eye • Arc height at axle seat • Spring rate • Normal static loading • Available space for spring width
- 8. 4. Problems withConventional Leaf Springs • Research about wt. reduction with stable design of vehicle • Steel leaf springs make it heavy and affects performance • Vertical forces on spring eye causes early failure • Depletion of natural resources from mines • Development in composites give properties needed for suspension
- 9. 5.Composite Materials •Definition - Structural material with two or more combined constituents at macroscopic level & not soluble in each other Reinforcing Phase forms- Fibers , particles , flakes Matrix Phase- Continuous Materials E.g.- concrete reinforced with steel epoxy reinforced with Graphite fibers reinforced phase Matrix phase Composite
- 10. 5.1. Classification Composites Matrix Based Polymer Matrix Metal Matrix Ceramic Matrix Reinforcement Based Fiber Reinforced Whisker Reinforced Particle Reinforced
- 11. 6. Fabrication Techniques • Different loading, various materials & Application feasibility Constant thickness, constant width design Constant thickness, varying width design Varying width, varying thickness design • Constant cross section design, hand lay-up process is used to study • Unidirectional GFRP material
- 12. 7. Hand Lay-UpProcess • Reinforcement & painting with matrix resin layer by layer • Template(Mould die) • Releasing agent(gel/wax) for surface finish • Uniform application, roller to remove trapped air • Duration-30 mins • Mould allowed to cure for 4-5 days at room temperature
- 13. 7.1. Sheet Preparation • Template - Aluminium Frame • Wt of glass-fiber sheet 150 gms • Epoxy resin with Hardener(9:1) • Releasing agent - Silicon gel • Repeat process till desired thickness is obtained • After curing, sheet pulled out Cut in design dimensions • Sometimes Heat is used for proper setting of fiber layers
- 14. 8. Experimental Tests • 1.Flexural Test Rectangular cross section bar deflected at constant rate 3 point bending, load at center Universal Testing Machine- 3 point Flexural fixture • 2. Tensile Test Force needed by composite till breaking point Extensometer or Strain Gauge Elongation , Tensile Modulus & Stress-Strain Diagram • 3. Impact Test Force for breaking under high speed tensile load Pendulum strike on anvil at specimen Impact energy using TMI Impact Tester
- 15. 9. Advantages &Disadvantages Advantages • Lightweight, extremely strong • Weigh ¼ th for same strength • Corrosion & chemical Resistance • Excellent elastic properties • Regains shape after bending till certain limit , useful for spring applications Disadvantages • High cost of fabrication , complicated time consuming process • Repair procedure is complex • Unpredictable mechanical characterization • Not isotropic , need more parameters for evaluation • Compressive strength not dependable
- 16. 10. Discussion &Conclusion Stress developed found well within limits with good factor of safety Longitudinal orientation of fibers in laminate offers strength Deflection is less compared to steel for same loading condition Bending stress lowered Conventional leaf springs 3.5 times heavier than Composite springs Material saving achieved
- 17. Lighter andeconomical for use but sensitive to heat cycles Sometimes heat treated for more stiffness High strength retention at severe environments Good alternative for steel in suspension applications In future, experimental verification for Bending, Torsion and Hardness to be done Cost reduction and optimum fabrication process development for mass production