# Machinable Glass-Ceramic

Machinable glass-ceramic is a glass-type material. It has the highest fracture toughness among the glass and glass-ceramics in the database. The graph bars on the material properties cards below compare machinable glass-ceramic to other glass and glass-ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

## Mechanical Properties

Compressive (Crushing) Strength

310 *MPa* 44 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

67 *GPa* 9.7 *x 10 ^{6} psi*

Flexural Strength

96 *MPa* 14 *x 10 ^{3} psi*

Fracture Toughness

2.5 *MPa-m ^{1/2}* 2.3

*x 10*

^{3}psi-in^{1/2}Knoop Hardness

250

Poisson's Ratio

0.29

Shear Modulus

26 *GPa* 3.7 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

84 *MPa* 12 *x 10 ^{3} psi*

## Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

6.0

Dielectric Constant (Relative Permittivity) At 1 MHz

6.4

Dielectric Strength (Breakdown Potential)

27 *kV/mm* 1.0 *V/mil*

Electrical Dissipation At 1 Hz

0.0049

Electrical Dissipation At 1 MHz

0.0050

Electrical Resistivity Order of Magnitude

14 *10 ^{x} Ω-m*

## Other Material Properties

Density

2.7 *g/cm ^{3}* 170

*lb/ft*

^{3}Maximum Temperature: Mechanical

760 *°C* 1400 *°F*

Specific Heat Capacity

790 *J/kg-K* 0.19 *BTU/lb-°F*

Thermal Conductivity

1.2 *W/m-K* 0.68 *BTU/h-ft-°F*

Thermal Expansion

21 *µm/m-K*

## Common Calculations

Stiffness to Weight: Axial

14 *points*

Stiffness to Weight: Bending

51 *points*

Strength to Weight: Axial

8.8 *points*

Strength to Weight: Bending

16 *points*

Thermal Diffusivity

0.56 *mm ^{2}/s*

Thermal Shock Resistance

4.3 *points*

## Followup Questions

## Further Reading

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015