Lightweight, High Performance Composites – What is a Composite Material?

21
Apr

Question: What is a composite?

Answer: One could write endlessly about this topic, but I’ve provided some basic information and a few FAQs to get you started.

Composite:

“A composite is a structural material that consists of two or more combined constituents that are combined at a macroscopic level and are not soluble in each other. One constituent is called the reinforcing phase and the one in which it is embedded is called the matrix. The reinforcing phase material may be in the form of fibers, particles or flakes. The matrix phase materials are generally continuous." Kaw, Autar K. Mechanics of Composite Materials.Boca Raton, FL: Taylor & Francis, 2006. Print. Page 2.

In other words

Composite = Matrix + Reinforcement

If you want an analogy, imagine an ice cube with numerous toothpicks embedded inside. The ice is the matrix and the toothpicks are the reinforcement.

Below I have noted some common types of reinforcement and matrix.

Reinforcement Phase 

Types of Reinforcement Relevant Materials Image Examples
Particulate Aluminum, Silicon Carbide
Microscopic view of Particulate Reinforcement Source
RVE of a Particulate Reinforced Composite
RVE of Another Particulate Reinforced Composite
Flake Glass, Mica, Aluimnum, Silver
Chopped Carbon Fiber Source
Mica Flakes Source
Fibers Glass, Graphite/Carbon, Aramid/Kevlar
Long Continuous Fibers in a Carbon Mat Source
Short Chopped Fibers Source
Microscopic View of Glass Fiber Polymer Matrix Composite Laminate Source
Microscopic View of Short Chopped Fiber Polymer Composite Source 

 

Matrix Phase

Types of Matrix Phases Composite Classification Relevant Materials
Polymer Polymer Matrix Composites (PMCs) Epoxies, phenolics, acrylic, urethane, and polyamides
Metal Metal Matrix Composites (MMCs) Aluminum, magnesium, titanium, cobalt
Ceramic, including Carbon Ceramic Matrix Composites (CMCs) Carbon, Silicon Carbide, Alumina, Mullite

 

What is the naming convention for composites? I'm not sure if there is a standard naming convention. Generally, you would need to describe the reinforcement phase and then the matrix phase.

Examples

  • Glass Fiber Polymer Matrix Composite
  • Short Fiber Reinforced Plastic
  • Carbon Reinforced Polymer

How would you analyze, through simulation, long fiber composites, commonly known as Composite Laminates? Every lamina in a laminate may be modeled as orthotropic, and there are some FEA program such as Marc or MSC Nastran capable of accurately representing Composite Laminates.

Carbon Fiber Polymer Matrix Composite Source
 
Glass Fiber Polymer Matrix Composite Source

 

How would you analyze, through simulation, particulate, nano, or short fiber composites? These are a bit more challenging to analyze since the material is best defined as anisotropic. You can use an FEA program such as Marc or MSC Nastran, but you would need to supply your FEA with anisotropic material data provided by Digimat.

Short Fiber Polymer Matrix Composite
 
Short Fiber Polymer Matrix Composite
 

 

Micromechanical Analysis
The last two questions were regarding macromechanical analysis. Now, given the need to perform micromechanical analysis, how would you analyze composites through simulation? You can use Digimat to determine the constituitive behaviors of composites all before the first physical test.

Microscopic View of Glass Fiber Polymer Matrix Composite Laminate Source

RVE_ContinuousFiber

MicroscopicRepresentative Volume Element Ready to Be Analyzed

Do you have a question? Email me at email.

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