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 MODIFIED COMPLETELY

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

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

Polymeric Material Types 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

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

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.

Role of Fiber & Matrix Role of Matrix Role of Fiber 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

Fiber/Matrix Bonding Quality and Resulting Failure Modes 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

Processes For Getting Resin Onto the Fiber 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)

Solution Prepregging Using the Dip Tank Method Solution Prepregging Using the Dip Tank Method

Prepregging Challenges 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 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

Vacuum Bag: Oven/Autoclave Cure

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

Autoclave state-of-the-art (Vought Aircraft; Charleston, SC) Autoclave state-of-the-art (Vought Aircraft; Charleston, SC) - Inside working diameter: 30ft. (9.26M) - Outside diameter: 32ft. (9.88M) - Inside working length: 76 ft. (23.5M) - Overall length: 112 ft. (34.5M) - Vessel volume: 82,000 cu.ft. - Max temperature: 450F - Max pressure: 150 psig - Heating system: 40 million BTU Control system: CPC Level III - Weight: over 1,000,000 lbs. - Man-hours to construct: 65,000+

Vacuum Assisted Resin Transfer Molding 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

Melt Viscosity of Comparison Materials Melt Viscosity of Comparison Materials

Composite Fabrication: Technical Challenges 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

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. MODIFIED COMPLETELY