Composites Joining PDF

Manufacturing II: Machining, Assemblies and Recycling  Product fabrication (PMCs) – From Ch.1 Forming As opposite to metals, composite parts are not intensively Machining machined...

Manufacturing II: Machining, Assemblies and Recycling  Product fabrication (PMCs) – From Ch.1 Forming As opposite to metals, composite parts are not intensively Machining machined Special tools and techniques are required Joining Finishing Main objectives of machining composites: Create holes, slots or some other features that are not possible to obtain during manufacturing Reach desired tolerances Surface preparation Surface finish Prototyping Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI DIM-ICAI – Javier Javier Escuela Técnica Munilla Munilla Superior de Ingeniería ICAI 05 de julio de 2012 2  Product fabrication (PMCs) – From Ch.1 Forming The possibility of manufacturing composites in complex Machining shapes reduces the number of joints, but sometimes they Joining cannot be avoided. Finishing Also, assemblies need joints Types of joints: Adhesive bonding Mechanical joints Direct Ancillary parts Physical/chemical joints For PMCs, adhesive bonding is usually preferred for parts and adhesive or bolted joints for assemblies Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI DIM-ICAI – Javier Javier Escuela Técnica Munilla Munilla Superior de Ingeniería ICAI 05 de julio de 2012 3  CM Manufacturing: Assemblies ▪ Machining ✓ Reinforcement ▪ Strong ❑ Conventional machining of ▪ Brittle ductile metals: ▪ Usually low thermal ▪ Shearing, plastic conductivity deformation ✓ Matrix ❑ While at PMC: ▪ Weak ▪ Brittle fracture, not steady state ▪ Less brittle ▪ Low thermal cond. and temp. resistance Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 4 4  PMC: Conventional Machining Turning Milling Abrasive cutting Drilling and Grinding Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 5 5  PMC Machining ▪ General challenges: ✓ Coolants and speed, tool materials ✓ Moisture absorption ✓ Thermal stresses ✓ Dimensional accuracy ✓ Edges quality ✓ Short chips, non homogeneous ✓ Behavior dependent on constituents properties, volume fraction, … Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 6 6  PMC Machining Chip formation: Ductile vs Brittle Brittle: ▪ Worse surface quality ▪ Force oscillations ▪ Dust ▪ Surface defects Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 7 7  PMC Machining: Surface vs angle Machined CFRP PEEK – 30% glass fibre Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 8 8  PMC: Non conventional machining Abrasive WaterJet (AWJ) Laser Abrasion Up to tens of mm thick (mov) Tolerances 0,05 – 0,15 mm Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 9 9  PMC: Non conventional machining Laser Machining Vaporization Few mm thick Tolerances 0,1 mm (mov) Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 10 10  PMC: Non conventional machining Erosion Electrical discharge (EDM) Up to cm3/h Tolerances up to 0,01 mm Die sinker EDM system Hole machined on CFRP by EDM EDM & WEDM Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 11 11  PMC Assemblies: Joints ▪ General challenges of joining: ✓ A joint is a source of stress concentration ✓ It creates discontinuity in the load transfer ✓ Labor-intensive process ✓ Add manufacturing time and costs ▪ In PMCs: ✓ Adhesive bonding ✓ Mechanical joints This chapter is just about structural joints. Specific challenges and strategies could be found when further specifications are needed: Pressurized fluids, electrical connectors, power transmission, vibrations, force limiters , environmental constrains…. Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 12 12  Mechanical joints Types of mechanical joints Riveted joint Single Lap Double Lap Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 13 13  Adhesive bonding vs Mechanical joints ▪ Adhesive bonding: ▪ Mechanical joints: ✓ Distribution of load ✓ No need for surface preparation ✓ Better fatigue and vibration properties ✓ No need of curing agents, heat and time ✓ Less weight ✓ Non toxic materials ✓ Joint is sealed ✓ Less training for operators ✓ “Absorbs” small geometric mismatches ✓ Easier dis-assembly ✓ Usually cheaper ✓ Easier quality inspection Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 14 14  PMC Assemblies Threaded joints ▪ How to improve threaded joints? ✓ Sealants ✓ Washers: elastic, contact deformation,… Wedge locking washer (mov) Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 15 15  PMC Assemblies ▪ Threaded joints. Other issues Soft or brittle materials. Example. Steel screw on copper part Dissimilar materials,… Avoid screws, select bolt+nut Inserts Helicoil ® Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 16 16  PMC Assemblies Riveted joints ▪ Easy to apply, even automated ▪ Reliable ▪ Low thermal effects ▪ One single use* ▪ More difficult to dismantle ▪ Also riveted nuts Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 17 17  PMC: Non conventional machining Self-piercing riveting Pre-drilled holes are not required! (mov) Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 18 18  PMC: Non conventional machining Clinching Local cold forming Just for metallic sheets No rivets or ancially parts needed (mov) Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 19 19  CM Assemblies: Joints ▪ In MMCs & CMCs: ✓ Mechanical joints ✓ Chemical bonding: Melting Welding Brazing Soldering Diffusion Chemical compound at interface Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 20 20  CM Assemblies: Joints Are base metals melted? Is a filler needed? Typ. Temp. Result ▪ Welding Yes Sometimes >Tm Strong, tight fit ▪ Brazing Never Always 400-800 ºC Tight fit ▪ Soldering Never Always (solder) < 400 ºC Soft joint Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 21 21  PMC Assemblies ▪ Special joining method for composites: Co-curing ✓ “Small” parts can be added to the part and covered by the same material ✓ This can be done before or after curing the substrate (Co-bonding) ✓ Complex shapes are possible in a unique part ✓ Important local effects arise: This should be evaluated ✓ Difficult inspection and repair Cocured Bonded Instituto de Investigación Tecnológica Eva Paz Jiménez DIM-ICAI Javier Munilla Escuela Técnica Superior de Ingeniería ICAI 05 de julio de 2012 22 22 Main references: Composite Materials. Science and Engineering. K. Chawla. Springer Composites Manufacturing. Materials, Product and Process Engineering. S.K. Mazumdar. CRC Press Introduccion a los materiales compuestos estructurales. Instituto Nacional de Técnica Aeroespacial, INTA Machining of Polymer Composites. J.Y. Sheikh-Ahmad. Springer