Composite Materials

Resistance Welding Lesson Objectives When you finish this lesson you will understand: Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords

Matrix Materials Magnesium Lowest density (37% lighter than aluminum) Aerospace applications Creeps at low temp Relatively low strength Prone to variety of corrosion problems Aluminum Easy to process, inexpensive Density only 35% of Steel Can be alloyed to fairly high strengths 57% stiffer than Magnesium Excellent corrosion resistance Most widely used material

Matrix Materials Titanium Twice as strong as aerospace aluminum 65% heavier than aluminum, but 65% stiffer Temp & corrosion resistant = use in demanding environments Copper, Iron, Nickel, Tungsten Special use alloys Electronic Circuits Metal forming dies Jet engines Military applications

Reinforcements Ceramics Silicon Carbide (SiC) Aluminum Oxide (Al 2 O 3 ) Titanium Carbide (TiC) Boron Carbide (B 4 C) Other Graphite (C) Titanium Diboride (TiB 2 ) Metal Filaments Boron Steel Tungsten Choice of matrix and reinforcement depends on: Desired properties of composite Compatibility between matrix and reinforcement MMC Processing route

Rule of Mixtures

Designation for MMC Matrix + Reinforcement / Volume % Form Matrix = metal or alloy designation of matrix Reinforcement = chemical formula of reinforcement Volume % = Volume percent without the % sign Form = Form of the reinforcement f, fiber or filament c, chopped fiber w, whisker p, particulate Example: SiC/20w

Welding Handbook, AWS

Particulate Composite Short-Fiber Composite Long-Fiber Composite Laminated Composite Manufacturing Processes Welding Handbook, AWS

Processing Methods Solid State Semi-solid Liquid

Solid State Processing Bonding of continuous fibers between metal foils to make panels Aerospace Applications Ti/Sic; Al/B Laminated Composite Powder Metallurgy Mix particles of matrix with reinforcement Vacuum hot press (near solidus) Extrude or roll Al/B 4 C; Al/SiC

Semi-Solid Processing Spray Deposition Chilled Plate MMC Build Up Flame Spray Matrix Flame Spray Reinforcement ……….. Rheocasting Mix reinforcement into matrix held between solidus and liquidus x

Liquid Processing Infiltration Interfacial reactions can be a problem

Applications - From Ukraine Krivov, Optimization of design-production…, Welding in the World, Nov-Dec 1994

Applications Krivov, Optimization of design-production…, Welding in the World, Nov-Dec 1994

Krivov, Optimization of design-production…, Welding in the World, Nov-Dec 1994

Welding Handbook, AWS

Detrimental Weld Pool Chemical Reactions [l] indicates liquid phase [s] indicates solid phase [Al l ] indicates in solution with liquid aluminum

Resistance Welding Arc Welding Time-Temp Effect of Chem Reaction Welding Handbook, AWS

Capacitor Discharge Stud Welding Solid State Fusion Weld Brazing

Capacitor Discharge Stud Welding MMC Materials Welded 6061, 2024, 6061/SiC/40p, 6061/SiC/48f, 6061/B 4 C/30p, AZ61/B 4 C/40p Studs = 0.25 in; Sheet=0.13 in Time = 0.4 ms Solidification rate = 10 6 C/s

Welding Handbook, AWS Stud Welding

Welding Handbook, AWS

Capacitor Discharge - Solid State Welding Ti-6Al-4V/SiC Sheets Ti-6Al-4V/SCS-6 Diffusion (solid state) Bond No Melting Failure Occurred Upon Loading Remote from Weld Interface Baeslack & Froes, Joining Similar & Dissimilar……, JOM March 1995 SCS-6 is a complex fiber with SiC vapor deposited onto a graphite carbon core

Increase in Welding Current (Voltage) Causes Change From Solid State to Fusion Weld Cox et al, Capacitor Discharge RSW of SiC Fiber… Welding Journal, Oct 1993

Capacitor Discharge Solid State Weld No liquid - Weld Strength 80% of Monolithic SCS-6 Fiber Cox et al, Capacitor Discharge RSW of SiC Fiber… Welding Journal, Oct 1993

Solid State Weld with no Fiber degradation Cox et al, Capacitor Discharge RSW of SiC Fiber… Welding Journal, Oct 1993

Capacitor Discharge - Fusion Welding

Partial Melting Fusion Weld Cox et al, Capacitor Discharge RSW of SiC Fiber… Welding Journal, Oct 1993

Solidified Liquid around fiber, Property degradation Cox et al, Capacitor Discharge RSW of SiC Fiber… Welding Journal, Oct 1993

Al-7Zn/C BAlSi-4 Brazing Foil Low force = expulsion > 400 lb = fiber packing at weld center (see next slide) Spot Brazing Continuous C Fiber MMC

Welding Handbook, AWS Brazing

Spot Brazing Continuous SiC Fiber MMC Ti-22Al-23Nb/SiC Ti-Cu-Ni Braze Foil Baeslack & Froes, Joining Similar & Dissimilar……, JOM March 1995

Baeslack & Froes, Joining Similar & Dissimilar……, JOM March 1995

Resistance Welding Arc Welding Time-Temp Effect of Chem Reaction Welding Handbook, AWS

Resistance Spot Welding Solid State With Melting/Solidification

Spot Welding Welding Handbook, AWS

Adjusting Welding Force Welding Time To Avoid Fiber Crushing in Al/B MMC Welding Handbook, AWS (Continuous Fiber)

Aluminum/Boron Continuous Fiber Hersh, Resistance Spot Weld MMC, Welding Journal, June 1970

Aluminum/Boron Continuous Fiber Hersh, Resistance Spot Weld MMC, Welding Journal, June 1970

Aluminum/Boron Continuous Fiber Hersh, Resistance Spot Weld MMC, Welding Journal, June 1970

Aluminum/Boron Continuous Fiber Hersh, Resistance Spot Weld MMC, Welding Journal, June 1970

Aluminum/Boron Continuous Fiber Hersh, Resistance Spot Weld MMC, Welding Journal, June 1970

Spot Welding Discontinuous Fibers Segregation of reinforcement (see next slide)

Welding Handbook, AWS