Composite Materials Dr. Jing LI 13661954020 55271689 lijing6080@usst.edu.cn 2014-2015 Fall Semester

Definition of Composite Materials A multi-phase material, consisting of two or more physically distinct and mechanically separable constituents. One phase is usually continuous and is designated the “matrix” The other phase(s) are reinforcements distributed within the matrix and may be fibrous or particulate In some composites there may be two interpenetrating continuous phases.

Composites offer High Strength Light Weight Design Flexibility Consolidation of Parts Net Shape Manufacturing Functional Properties Electrical conductivity Thermal management Physical barriers

Classification of Composites (I) 1) Natural Composite Materials: Wood; bamboo; bones; muscles and other tissues 2) Microcomposites Metallic alloys, Polymer blends, Fibre reinforced composites (PMCs, MMCs, CMCs); Particulate reinforced composites 3) Macrocomposites Coated sheets-galvanized steel Laminate composites Sandwiches-honeycomb and foam structure 4) Nanocomposites Polymer composites reinforced with clay minerals, BN, fullerence, Carbon nanotubes, Graphene.

Classification of Composites (II) Particulate Fiber Structural Large Dispersion Laminates Sandwich Particle Strengthened Panels Continuous Discontinuous Aligned Random Particle size< 10-8m

Classification of Composites (III) Metal matrix composites Ceramic matrix composites Polymer matrix composites

Design Project Propose a project which designs one composite materials. The project must have a real application Send me the project title by the end of week 7 (October 11th). The title must clearly indicate what product will be designed.

Design Project Present the project on December 16th Including the survey of the materials in the commercial products. (the fulfilled properties, the critical properties, the desired properties) The composite materials design. (matrix, reinforcement, the geometry, advantage) Calculate the filler content according to the required material properties. Proposed fabrication method. Discussion and Conclusion：Is your design better than the commercial available products.

Properties of Composites Dependent on: Constituent phases relative amounts geometry of dispersed phase shape of particles particle size particle distribution particle orientation Interface properties Processing Methods

Functions of Matrix (Primary phase) Continuous phase Provides the bulk form of the part or product. Supporting the fibre Holds the imbedded phase in place, usually enclosing and often concealing it . Providing adequate environmental protection Transfer of load through the fibre-matrix interface (mainly by shear)

Matrix Considerations End Use Temperature Toughness Cosmetic Issues Flame Retardant Processing Method Adhesion Requirements

The Reinforcing Phase (Secondary Phase) A reinforcement is the strong, stiff integral component of a composite which is incorporated into the matrix to achieve desired properties Imbedded phase is the most common one The secondary phase can take the form of an infiltrated phase in a skeletal or porous matrix Example: a powder metallurgy part infiltrated with polymer

Functions of reinforcements Function is to reinforce the primary phase The term ‘reinforcement’ implies some property enhancement Fibres or Filaments: continuous fibres, discontinuous fibres, whiskers Particulates reinforcements may be of any shape, ranging from irregular to spherical, plate-like or needle-like, nanoparticles (clay, carbon black)

Textile Structure Unidirectional Woven Braid

The Interface There is always an interface between constituent phases in a composite material For the composite to operate effectively, the phases must bond where they join at the interface Figure ‑ Interfaces between phases in a composite material: (a) direct bonding between primary and secondary phases

Interphase In some cases, a third ingredient must be added to achieve bonding of primary and secondary phases Called an interphase, this third ingredient can be thought of as an adhesive Figure ‑ Interfaces between phases: (b) addition of a third ingredient to bond the primary phases and form an interphase

Characteristics of Composites Heterogeneity Composites are always heterogeneous, often at several different level of structure. They cannot be treated as “continuous solids”. Fibre: 1.0 –20 mm Lamina: 0.1 –1.0 mm Laminate: 1.0 –100 mm Component: 0.1 – 10m Property Relationships Their properties are determined by those of constituents, their relative concentrations, their geometric arrangement, manufacturing processes and the nature of the interface between them. Anisotropy Composites are sometimes strongly anisotropic: properties are different in one direction than in another. This requires a fundamentally different approach to both design and manufacture. Fibre/Laminate: axial/transverse

Advantages of Composites Mechanical High specific stiffness and strength Enhanced Toughness Enhanced fatigue properties Better damage tolerance Physical Controlled thermal expansion and conductivity Directional electrical and magnetic properties Better elevated temperature behaviour Better barrier properties Chemical Enhanced corrosion and degradation resistance

Advantages of Composites in Service Structural efficiency Lower mass Longer (flight) range Lower fuel consumption Higher performance Enhanced Durability Longer life Extension of operating envelope (e.g. higher temp) Less maintenance Greater reliability Lower operating cost

Summary Definition of composite materials Classification of composite materials Functions of matrix and reinforcements Applications of composite materials Advantages of composite materials Factors determine the performace of composite materials