By brasco - 3/12/2013 2:37:31 AM
are we laying our lamina and just stacking them and not fully understanding the strength possible
with composites?
have any of you been able to examine your own products after failure or damage ?
i know this link i have is oriented towards aircraft, but some of it is also basic composites
fabrication as well. i am trying to work out the cost and labor end of how to make a good strong
part for automotive uses. waste is bad,this stuff is far too expensive to waste any of it.
so more exploration for me for my fabric stack-
i do think attention to the orientation of the layers is worth looking into.
i am unsure how this could effect out parts, but just stacking lamina at 0 and 90 sounds
like it could be damaged easier from impact. 0/90 and then alternating to 45 degrees seems to make
the stack quasi-isotropic.(strength in all directions of the lamina).
and then there is delamination damage,and that comes from impact damage ,and sometimes it is a built in defect
of the process.(hence the MUST BE THOROUGHLY MIXED nature of your resins)
holes drilled for bolts ,screws or rivets and holes cut for access etc all weaken the laminate. and dont slack off
when you make and trim and dress your edges of the panels, as delamination at an edge from impact damage
is easier to start, and you may not be able to detect this damage and repair it while doing the other repairs.heat
and water/rain exposure also effect the strength of our panels. IE for kayaks.
so my thoughts on damage of say a bonnet? well my own thoughts would to be to build a stronger part
if the cost is not significant. and if it is damaged, i'd rather the repair be smaller than if it were stacked at 0 and 90 and
the damage runs along the 0 or 90 plane. worst case is i dont want the vehicle occupants hurt from flying delaminated
parts or even bystanders either. if it cracks, delaminates,collapses, or otherwise breaks down i want it to stay together.
so i am not a doomsayer here, i was just reading up on how things are made and designed.
Laminate Design Principles
thanks for reading my ramblings 
Scott
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By NikCFC - 3/14/2013 3:04:24 PM
I agree with Warren and Fred, placing the fibers in different directions is more of a F1 and Aerospace thing where they need every little bit of strength and where cost isn't an issue. Placing Kevlar within the layers will hold it together, even using woven roving also 
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