Polymer Matrix Composites Matrix Resins and Composite Fabrication

Polymer Matrix Composites Matrix Resins and Composite Fabrication NESC Academy Materials Technology Discipline Team Brian J. Jensen, Ph. D. March, 2011 1

Objectives • Provide Introduction to Polymeric Matrices for Composites. • Provide Introduction to Processing of Polymeric Matrix Composites. 2

Outline Introduction to Polymers • • • Thermoplastics Thermosets Definitions Composite Fabrication Processes • • • Fabrication Methods Required Polymer Properties Advantages/Disadvantages 3

Polymeric Material Types Thermoplastics • High Molecular Weight (Large) • Nonreactive / Reprocessable • High Melt Viscosity Thermosets • Low Molecular Weight (Small) • Reactive / Crosslinked / Not Reprocessable • Low Melt Viscosity 4

Polymer Properties Controlled by Molecular Structure • Processability • Physical (Tg, CTE) • Mechanical (strength, stiffness) • Toughness • Solvent Resistance • Environmental Resistance (thermal, radiation) • Durability 5

Environments Affecting Polymer Durability • • • Temperature Stress Time Atmosphere Chemical, mechanical and electrical action Radiation Durability - Capacity of a material to retain useful properties for a required period of time under environmental conditions of application. 6

Role of Fiber & Matrix Role of Fiber • Carries In-Plane Loads: Provides stiffness & Strength • Reduces Thermal Coefficient Of Expansion Role of Matrix • Bonds and Holds Filaments In Place • Protects Filaments • Provides Transverse Strength • Acts As A Load Transfer Medium • Provides Interlaminar Toughness • Provides Durability 7

Fiber/Matrix Bonding Quality and Resulting Failure Modes Adhesive Failure – Undesirable Indicative of Weak Interfacial Bond Strength Cohesive Failure – Desirable Indicative of Strong Interfacial Bond Strength 8

Processes For Getting Resin Onto the Fiber • Prepregging Unidirectional Fiber – Prepregging Machine • Infusing Preforms – Resin Film Infusion (RFI) – Resin Transfer Molding (RTM) – Vacuum Assisted Resin Transfer Molding (VARTM) 9

10

11

Solution Prepregging Using the Dip Tank Method 12

13

Prepregging Challenges 1) Proper tack over long period at RT 2) Proper drape over long period at RT 3) Acceptable RT out-time; good prepreg stability 4) Proper fiber/resin ratio 5) Parallel fiber alignment, minimum overlaps, splits, surface imperfections, hair balls 6) Solvent removal to acceptable level 7) 100% wet-out of filaments 8) Automated control to achieve reproducibility 9) Creel set-up and machine alignment 14

Vacuum Bag: Oven/Autoclave Cure 15

NASA Langley Research Center Autoclave Capabilities • 800°F • 400 psi • 24” x 48” 16

Autoclave state-of-the-art (Vought Aircraft; Charleston, SC) - Inside working diameter: 30 ft. (9. 26 M) - Inside working length: 76 ft. (23. 5 M) - Vessel volume: 82, 000 cu. ft. - Max pressure: 150 psig - Control system: CPC Level III - Man-hours to construct: 65, 000+ - Outside diameter: 32 ft. (9. 88 M) - Overall length: 112 ft. (34. 5 M) - Max temperature: 450 F - Heating system: 40 million BTU - Weight: over 1, 000 lbs. 17

Vacuum Assisted Resin Transfer Molding • Upper half of metal mold replaced by vacuum bag • Atmospheric pressure provides both the resin driving force and the preform compaction force • Distribution medium is used to facilitate the resin flow • Typically a room temperature process ROLE OF MATRIX • BONDS AND HOLDS FILAMENTS IN PLACE • PROTECTS FILAMENTS • PROVIDES TRANSVERSE STRENGTH • ACTS AS A LOAD TRANSFER MEDIUM • PROVIDES INTERLAMINAR TOUGHNESS • PROVIDES DURABILITY 18

Melt Viscosity of Comparison Materials 19

Composite Fabrication: Technical Challenges • Remove all air and volatiles so no porosity/voids • Debulk to desired and uniform net shape at all locations on the part - full consolidation • Achieve proper fiber/resin ratio • Achieve reproducibility from part to part • Minimize warping and microcracking • Minimize scrappage and cold storage • Try for non-autoclave processing where possible • Be cost effective: automation; effective process models; in-process control with in-line NDE; short cure cycles; low part count; simple tooling 20

Summary Polymer matrix composites are prepared by combining a matrix resin with fibers. The matrix resin bonds the fibers together and protects them. The fibers provide the capability to carry large loads efficiently. When the proper combination of matrix resin and fiber type is selected and a fabrication process resulting in a high quality composite is utilized, highly efficient and durable structures can be prepared with the required combination of properties for many different high performance applications. 21