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JaredOSU
05-03-2014, 04:54 PM
What is the best type of fiberglass for strength? Woven or chopped? I'm reinforcing for a tower.

CCAnderson
05-13-2014, 02:45 PM
Each has it own merits. The strength in fiber glass lies in the same direction as the glass strands. woven is very strong in 2 directions like a woven fabric. Try pulling with the strands then try pulling at a 45 degree angle. Chopped is less strong then woven in two directions but has good strength in all all directions.

drschemel
05-13-2014, 03:50 PM
the fiberglass makes a thinner layer than the woven mat does so you can lay several layers for the same overall thickness. To my thinking, it would work better for the reinforcing you are going to be doing.

chrislandy
05-13-2014, 04:32 PM
Look at triaxial or biaxial glass, it's much better than both woven and CSM. CSM has less than 30% of the strength and stiffness of UD/bi-axial/triaxial in one direction, woven is 50-70% depending on the weave.

With triaxial you have unidirectional fibres placed at 0, +45 & -45 degrees, biaxial is typically +/-45 so you could use 2 layers of biaxial placed at 45deg to each other so you cover 0, +45, -45 & 90deg.

CSM is used these days as a bulking layer.

Are you looking to strengthen against pull-out or bolt bearing/shear? for both you will need thickness. I'm assuming you'll use polyester resin, if it was me, I'd be going 2 layers of 9oz (or lighter) biaxial glass at 45deg to each other, cure to tack then repeat a few times to build up the thickness (assuming you are working upside down!)

GoneBoatN
05-13-2014, 05:03 PM
This may be of some help too you - http://www.westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

From page 18 - "As noted in the introduction, doubling the thickness of a laminate will increase its stiffness by eight times."

From page 16 - "For stress reduction, step the edges of the fabric to create a tapered edge."

See page 4 for for comments about epoxy vs polyester.

Lots of good information in this guide an well worth reading.

mikeg205
05-13-2014, 06:49 PM
look in the library good video from Tap plastics.. you even go kevlar if you were so inclined ;)

https://www.youtube.com/watch?v=ioj1YBm6bJY