GT ME 4793 - Compression Molding (6 pages)

Previewing pages 1, 2 of 6 page document View the full content.
View Full Document

Compression Molding



Previewing pages 1, 2 of actual document.

View the full content.
View Full Document
View Full Document

Compression Molding

30 views


Pages:
6
School:
Georgia Tech
Course:
Me 4793 - Composite Mater& Process
Unformatted text preview:

Compression Molding ver 2 ENG 4793 Composite Materials and Processes 1 ENG 4793 Composite Materials and Processes 2 Schematic of a Compression Molding Press ENG 4793 Composite Materials and Processes 3 ENG 4793 Composite Materials and Processes 4 5 ENG 4793 Composite Materials and Processes 6 Matched Die Mold ENG 4793 Composite Materials and Processes 1 Typical products Lightweight Durable Aerodynamic styling Front and rear end automobile panels Hoods Roofs Scoops Fenders Spoilers Air deflectors Lift gates Battery trays ENG 4793 Composite Materials and Processes 100 SMC parts 450 lb truck 114 million lb 1996 7 ENG 4793 Composite Materials and Processes 8 Advantages and disadvantages Car parts by SMC Prowler Advantages Short cycle time typically 1 6 minutes High volume production Class A high quality surfaces Disadvantages High initial capital investment Labor intensive Secondary operations are sometimes required ENG 4793 Composite Materials and Processes 9 ENG 4793 Composite Materials and Processes 10 Three Thermoset Material Types Thermoplastic SMC Preform Molding Shaped dry reinforcement Binder Matrix as liquid or powder Azdel BMC Bulk Molding Compound Molding PP matrix glass fiber mat 30 40 by weight Fibers 30 and 1 inch Resin about 25 Filler about 40 Log or rope form continuous chopped directionalized SMC Molding Fibers 30 50 by weight Fibers 1 3 inches to continuous Resin about 25 Filler 25 45 Thin flat Sheet Molding Compound ENG 4793 Composite Materials and Processes 11 ENG 4793 Composite Materials and Processes 12 2 ENG 4793 Composite Materials and Processes 13 ENG 4793 Composite Materials and Processes 14 SMC manufacture using a configuration that can make chopped fiber SMC R continuous fiber SMC C or continuous random SMC C R material ENG 4793 Composite Materials and Processes 15 SMC Component Weight Percent Styrene 13 4 Polyester 10 5 Glass fiber Calcium carbonate Low profile agent LPA 30 0 Initiator 1 00 Magnesium hydroxide Zinc stearate 40 0 3 45 ENG 4793 Composite Materials and Processes 16 High Strength SMC Function Reactive monomers that provide a cross linking structure Reactive monomers that provide a cross linking structure Reinforcement Filler increases bulk volumeand reduces part cost Controls part shrinkage a thermoplastic additive Provides free radicals to initiate polymerization 0 70 Increases viscosity 1 00 Lubricant mold release agent ENG 4793 Composite Materials and Processes 17 ENG 4793 Composite Materials and Processes 18 3 Polyester Epoxy Polyesters can be thermosets or thermoplastics Do not emit gases during cure Compared to polyesters Thermoset polyesters such as those used in compression molding are formed from linear unsaturated thermoplastic polyesters which are crosslinked during a cure reaction Higher mechanical properties Longer cycle times Less desirable surface appearance Special features of polyester resins Does not emit gases byproducts during cure Most common ENG 4793 Composite Materials and Processes 19 ENG 4793 Composite Materials and Processes Other resins 20 Molding process Phenolic Urea Melamine All three of these emit gases condensation products during cure Gas emission can lead to voids in the final product an obvious disadvantage ENG 4793 Composite Materials and Processes 21 ENG 4793 Composite Materials and Processes SMC cycle Geometry factors ENG 4793 Composite Materials and Processes 22 23 Wall thickness of part Charge area vs mold area Charge placement location Single or multiple charges ENG 4793 Composite Materials and Processes 24 4 Curing Time vs Mold Temperature for SMC sheets Manufacturing Factors Mold wall heating Closing rate Maximum clamping force Gel time Mold filling should be complete before the resin gels De molding time Time to attain a sufficient degree of cure to demold the part ENG 4793 Composite Materials and Processes 25 Viscosity variation of an SMC before and during the compression molding operation ENG 4793 Composite Materials and Processes 27 Fiber orientation ENG 4793 Composite Materials and Processes 26 Flow of various layers of an SMC charge during compression molding ENG 4793 Composite Materials and Processes 28 Fiber orientation Planar two dimensional fiber orientation Fibers aggregate to form bundles Compaction of bundles to produce swirling Principal direction changes throughout plaque because flow direction varies Most affected by amount of flow ENG 4793 Composite Materials and Processes 29 ENG 4793 Composite Materials and Processes 30 5 Effect of cure time on the development of flexural strength in a compression molded SMC R laminate ENG 4793 Composite Materials and Processes Various defects in a compression molded SMC part 31 Common Surface Defects in Compression Molded SMC ENG 4793 Composite Materials and Processes Matched Die Molding Evaluation Investment High Capital equipment High tooling Materials Fast cure preferred Low or no volatiles New for thermoplastics Mostly chopped fibers Processing Fast 1 10 min cycles Low labor automated Hazards remote mold closed High Pressure 1 000 psi 7 MPa ENG 4793 Composite Materials and Processes 33 ENG 4793 Composite Materials and Processes 35 32 Quality Smooth surfaces both sides Voids cracking common Consistent parts Properties modest Products High volume Low cost Small projected areas Fairly complex shapes avoid undercuts ENG 4793 Composite Materials and Processes 34 6


View Full Document

Access the best Study Guides, Lecture Notes and Practice Exams

Loading Unlocking...
Login

Join to view Compression Molding and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Compression Molding and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?