Found at: Difference between fiberglass and G10?
G10 is simply a specification for a grade of fiberglass laminate composite made as commercial sheets
, rods and tubes.
G10 FR4 laminate grades are produced by inserting continuous glass woven fabric
impregnated with an epoxy resin binder while forming the sheet under high pressure. This material is used extensively in the electronics
industry because its water
absorption is extremely minimal and the G10 line of materials is not electrically conductive. The G10 FR4 is most commonly used in PCB (Printed Circuit Boards) applications. G10 exhibits superior mechanical and dimensional stability and doesn't shrink. Temperature ratings of 180 degrees C. In addition to these properties, G10/FR4 has excellent dielectric loss properties, and great electrical
strength. The difference between Grades G10 and FR4 is that FR4 is a fire retardant grade of G10. FR4 (also known as Garolite) can be substituted where G10 is specified; G10 can never be substituted for FR4. G10 is also known as Micarta and Garolite and can be used for structural supports, buss bars, mechanical insulation
, gears, test fixtures, washers, spacers and tight tolerance machined parts
for electromechanical assemblies. http://www.jjorly.com/g10_fr4_sheets_fabricator.htm
laminates are denser than most of their home made composite equivalents because the commercial processes do a better job of minimizing the epoxy fraction in the laminate which adds weight but not strength to the composite.