BDCS Notes - Properties of Composites

Properties of Composites

Composite materials are affected by:

1. Component properties

2. Volume fractions of components

3. Type and orientation of the dispersed phase

4. Bond between dispersed phase and matrix.

“The properties of the components can be viewed as the weighted averages of the properties of the components.”

Assumptions generally made to simplify the analysis of composite materials:

1. Each component has linear, elastic and isotropic properties.

2. A perfect bond exists between dispersed and matrix phases (no slipping).

3. The composite geometry is idealized and the loading pattern is parallel or perpendicular to reinforcing fibers.

LOADING PARALLEL TO FIBERS

Isostrain Condition – When loads are applied to aligned fiber-reinforced composites parallel to fibers, matrix and fiber phases deform equally.

e_c = e_m = e_f = e

e_c = total strain

e_m = composite

e_f = matrix strain

e = fiber strain

And the force applied to the composite F_c is the sum of the force carried by the matrix F_m and the force carried by the fibers F_f:

F_c = F_m + F_f

F_c = F_m + F_f

Thus, σ_cA_c = σ_mA_m + σ_fA_f

_{σi = stress of component i}

A_i = area of component i