Biaxial Weave Combined with Woven roving layup

Does anyone know which layer is usually best after the gelcoat (strength wise) and do you need to use any type of weave between to combine the two to prevent de-lamination? This area will experience lower forces and is there as a shell rather than structural (although will share some structural forces).

I'm attempting to create a light weight layup by using continuous strands. There's no access to any computer Aided programs to calculate the correct laminates so for the moment the plan is to use the best theory to hand.

I'm thinking of using a layer of Biaxial (45 deg) and one layer woven (90 deg) and Gel coat on the outer layer.

Thanks in advance!

 

If you like, you can use my SCT program, which calculates the scantlings for ships according to ISO 12215. The program can be downloaded from my website and can be used for free for 30 days.

 

Would very much appreciate the offer! Does the program work for with standard mono hull shapes, as the shape I'm creating is very unusual?

 

In general, the design pressures have nothing to do with the shapes of the boat. Some data, such as the deadrise angle, must be indicated by the user. The program interface tells you all the information it needs to perform the calculations. As far as the general data is concerned, it is the following:

GENERAL

Type of Hull Mono Hull or Multi Hull
Design category A "ocean", "B" or "C"
Power or Sail Motor or sail
Length of the Hull m
Length of the fully loaded waterline at mLDC m
Beam of the hull m
Beam of the fully loaded waterline at mLDC m
Chine beam m
Depth m
Draugth at mLDC (TC) m
Maximum speed at mLDC knots
Loaded displacement mass of the craft kg
Deadrise angle at 0.4 LWL forward of its aft end
Water specific gravity kg / m3​

 

Trying to get on your site although the flash player isn't allowing?

 

Send me your email by private mail and I will send you the link to download SCT.

 

Hi, Is this how you make a private reply? Testing

 

Try this link to download SCT : Hightail Spaces https://www.yousendit.com/download/dDZINnFKQk5sUjlEZU1UQw

 

To answer your first question, delamination in between layers is primarily dictated by the strength and thickness of the resin in between the cloth/fibers with resin being the weakest layer. Although there are many types of delamination, the most common is separation of the bondline caused by too much flexing or a large deflection caused by an impact. The second most common is the weakness of the bondline due to manufacturing process. Woven on top of woven is allowed as long as the succeeding layer is laminated while the first layer is still tacky. This provides a good adhesion by crosslinking of polymer in between layers.

Now, for the type of weave, fibers are strongest in the direction of the load applied along the fiber direction. Unidirectional fibers are strongest if the load is applied longitudinally but it is the weakest at the transverse direction. 0/90 degree woven fabrics are slightly weaker in the longtitudunal direction (compared to uni) because of the up and down direction of the weave. In the transverse direction, it will be more or less be the same weakness.

The 45 degree or biaxial will only be strong in the 45 degree direction but loses quickly its strength when loaded in the 0/90 direction. If it is a uni, about 10% of the strength remains. With woven 45 degree biax, about 25 % of the ultimate strength.

A uni is very strong at 0 degrees, about 4X that of a woven, but at around 7 to 10 degree off axis load, it starts to degrade quickly and becomes 10% of the ultimate strength even before the 45 degree is reached. This is the most common fault of those who substitute uni thinking it is stronger.

Lloyd's, BV and ISO has a formula to predict the strength but applies only to uni fibers. The formula is rather long and complex so be careful.

 

Great explanation. Many thanks, RX.

 

Print-through of the weave pattern could be a snag.

 

Of course, that is why many times 2 or 3 mats are placed before the outermost fabric.

 

The OP makes no mention of using mat anywhere, he is focussed on weight saving.

 

He will know what he does. Calculating the minimum weight compound does not consist of putting as few layers as possible, regardless of the minimum required strength or, the other option, minimum weight with minimal labor.