Composites basics

Question 1

Under transverse loading of a UD-composite, what are the stresses and strains in the fibers and matrix?

Answer 1

The stress is the same both in the fiber and matrix: σ_T = σ_f = σ_m

The strains are different due to different moduli:
e_f = σ_f/E_f
e_m = σ_m/E_m

Question 2

What is the simple model for the transvere modulus in a composite?

Answer 2

Question 3

What is the simple model for the longditudinal modulus in a composite?

Answer 3

(Rule of mixture)

Question 4

What is the Fiber Volume Fraction in a composite?

Answer 4

Question 5

What is the density of a fiber composite?

Answer 5

Question 6

What is the definition of a composite, with its limitations?

Answer 6

A material that consists of two or more materials with different properties. Limitations:
1. The different phases of a structural composite have distinct physical and mechanical properties
2. The characteristic dimensions are much larger than molecular dimensions

Question 7

What are the difference between isotropic and anisotropic materials?

Answer 7

• Isotropic: uniform properties in all directions
• Anisotropic: properties varies depending on the direction

Question 8

What is a fiber sizing and its functions?

Answer 8

Fiber sizing is a surface treatment applied to fibers to enhance their performance, handling, and compatibility with matrix materials in composite manufacturing.

Question 9

Under longdidtudinal loading of an unidirectional composite , what is the stresses and strains in the fibers and matrix?

Answer 9

Strain in the composite, fibers, and matrix is the same: ε_c = ε_f = ε_m

The stresses are different due to different moduli:
σ_f = E_f ε_c
σ_m = E_m ε_c