1. The American University in Cairo Mechanical Engineering Department MENG 426: Metals, Alloys & Composites Interactive MENG 426 Lab Tutorials Experiment (8) Al-SiC MMC Microstructure Prepared by Eng. Moataz M. Attallah Fall 2002

2. Experiment (8) Composite Materials Outline  Introduction: Composite materials  Advantages of composites  Types of composites  Particulate reinforced MMC  Objectives  Specimen  Results

3. Experiment (8) Composite Materials Composite Materials (I) Definition  A complex solid material composed of two or more material classes by physical bonding, insoluble on the macroscopic scale to produce a material who has hybrid properties of the classes properties.  No Chemical Reaction  No Alloy forms (substitutional/interstitial)  Properties produced

4. Experiment (8) Composite Materials Composite Materials (II)  A composite is composed of a matrix, which completely surrounds the reinforcement (either in fiber, powder, or particulate form).  A coupling/bonding agent (binder) has to be used to bond the different classes together.

5. Experiment (8) Composite Materials Composite Materials (III) Matrix  Soft phase (ductility/formability/toughness)  Polymer/Ceramic/Metal Reinforcement  Hard phase (stiff/hard/not formable)  Discontinuous/Continuous  Oriented/Disoriented  Oxides/Carbides/Nitrides/Fibers/Whiskers/ Particulates.

6. Experiment (8) Composite Materials Mechanical Behavior

7. Experiment (8) Composite Materials Advantages of Composites  Higher specific stiffness  Higher specific strength  Corrosion resistance  Toughness (impact strength)  Heat deflection temperature  Mechanical damping  Design flexibility  Manufacturing economy

8. Experiment (8) Composite Materials Design Flexibility

9. Experiment (8) Composite Materials Improved Properties http://www.uweb.ucsb.edu/~jess28/F-117.jpg

10. Experiment (8) Composite Materials Classification of Composites  By Reinforcement (Fiber reinforced /Particulate /Dispersion)  By matrix (metal matrix/polymer/metal)  By manufacturing method

11. Experiment (8) Composite Materials Particulate Composites  Examples: carbides, SiCw/Al, filled polymers, glass ceramics.  Strengthening Mechanisms: Matrix contraction, Particle strength, Residual stress, Control flaw size, Microcracking, Transform tough, Crack bridging, Crack deflection.  Load bearing member: shared  Reinforcement characteristics: Large particles >1µm, typically (5-10µm) with 0.1 to.95 Vf

12. Experiment (8) Composite Materials Other Types  Fiber Composites GFRP, CFRP, SiC-Ti, SiC-Al, etc..  Dispersed composites Age hardening alloys (experiment (#7))

13. Experiment (8) Composite Materials Particulate MMC  Properties depend on: 1. Particulate % 2. Size 3. Shape 4. Material

14. Experiment (8) Composite Materials Aluminum Matrix Composites Manufacturing Techniques  Solid State Process: Powder Metallurgy  Liquid State Process: squeeze casting/stir casting  Deposition processes

15. Experiment (8) Composite Materials Al-SiC MMC Microstructure

16. Experiment (8) Composite Materials Al-SiC MMC Applications

17. Experiment (8) Composite Materials Objectives  Understand the difference between a monolithic and a composite material  Understand the effect of the particle volume fraction on the mechanical properties and microstructure of a MMC  Pinpoint the defects & inhomogeneities in the composite structure

18. Experiment (8) Composite Materials Sample Preparation  Weigh powders acc. to fractions  Carefully blend to ensure homogenous mix  Hot compaction (120  C) of Al/SiC powders acc. to weight fractions, under 7 ton pressure  Sintering in furnace for three hours (540  C)

19. Experiment (8) Composite Materials Specimens  Pure aluminum  10% SiC  15% SiC  20% SiC Specimens prepared for metallographic investigation

20. Experiment (8) Composite Materials Lab Report  Sketch the four microstructures  Identify any defects in the composite structure  Study the effect of the reinforcement on the mechanical properties in terms of their measured RHN, and calculated tensile strength