Composite fiberglass/foam panel build question

#76
Yes that is one of our XPS samples. We have it in our program at special request. Don't be distracted by the blue color... XPS can come in all kinds of shades, from brown to yellow all depending on the chemicals used.

I find people in north america get too hung up on the XPS vs. PU specs. Yes, there are differences in both foams, many of them are already mentioned in the posts above. Composite panel construction has been implicated in the commercial trucking industry all over the world (except in NA) for more than 30 years. In fact, I just got back from a meeting in China with our Australian customer (one of the biggest truck body suppliers in AUS). For them using composites is the norm and they would never consider anything else. Therefore it's not "new" technology. 99% of those commercial trucks and Expedition Trucks are using PU foam cores without issues. Or at least with minimal issues (after all, anything can fail...)

In any case, here in NA private builders go with XPS because it's easier to buy. All other points are valid but wont really make the panel better or worse if done correctly.

For me personally, I would never use XPS as it's not easy to work with when you need to do repairs. XPS will desolve with most chemicals/resins.
 
#78
Bonding for all of these foams is affected by density and minimum compressive strength. With low minimum compressive strength, the foam crushes easily, eventually leading to delamination.
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I wanted to use the densest XPS I could get. Unfortunately, I couldn't get anything above 25psi without paying an exorbitant price. But after seeing what Dow and OC sell for panel core material, I'm not worried. Dow has 20, 30, and 40 psi core, and list the 30 psi variant as being for vehicles. https://www.dow.com/en-us/products/panelcorexpsinsulation
 
#79
at rruff
I found some Dow High Load 40 & 60 for a reasonable price by contacting a construction contractor who did occasional commercial refrigeration projects. For surfcraft, I would not go below 25 Psi. One solution used by surfboard builders is using wood veneer over lower density EPS foam (referred to as Compsand Builds) -- very durable builds. I have a blog post about XPS and EPS foam specs but am not allowed to post links in threads here. I will try to PM the link to you.

at Victorian
I am aware that there are several colors and brands of XPS. However, in the States, most people rarely look beyond "blue" and "pink" insulation foam.
Yes, polyester resin will dissolve XPS and EPS. However, epoxy resin does not.
If you do not need to sand or hotwire seams, I have found 3M 78 adhesive works well for bonding XPS.
XPS has its limitations. But for my purposes, minimal water absorption is a big plus.
 
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#81
But after seeing what Dow and OC sell for panel core material, I'm not worried. Dow has 20, 30, and 40 psi core, and list the 30 psi variant as being for vehicles.
Are you located in the States?
Have you been able to locate a dealer/retailer for the Dow Panel Core 20-30-40 XPS?
Looks like O-C makes their PinkCore Tight Tolerance Board in 15-25-40-60 XPS.
 
#83
Have you been able to locate a dealer/retailer for the Dow Panel Core 20-30-40 XPS?
Looks like O-C makes their PinkCore Tight Tolerance Board in 15-25-40-60 XPS.
As per Idasho, I guess there aren't any. The stuff at the hardware store is the same material, but the panel core sheets have been planed to tight tolerances. I've noticed the OC Foamular varies in thickness a bit, but I can deal with that.
 
#84
You can purchase both planed panels in the US, the only caveat is the volumes. I recall it was 60K SF. They are made to order special runs for both Dow and OC, and you don't have to get them in standard sheet sizes. They can do continuous length of close to 20 ft. The cost of those panels are almost double per SF vs standard "stamped" panels.
 
#85
Yep. That's the usual problem. The high density XPS foams don't have high public demand so they're not usually stocked by Lowes, HD and retail lumber outlets.
This last autumn I just discovered that HD in my area carries the Foamular 250 year-round.

BTW some of the surfboard epoxies are quick setting (e.g. Resin Research).

RR Kwik Kick:
Ambient Temperature
70F (21C) 80F (27C) 90F (32C)

Pot Life
18 min. 14 min. 11 min.

Set Time - Tack Free
1.5 hrs. 45 min. 30 min.

2. UV stability is excellent with little or no discoloration in over 1000 hours.

3. This system contains UV absorber which allows it to be used in conjunction with sensitive substrates. I.E. Urethane foam, PVC foam, light colored woods, etc.
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#86
OK, I reviewed this entire thread to make sure I wan't missing anything.

My interest in XPS is surfcraft construction (surfboards, body boards, etc.). Not soaking up water is a huge advantage for surfcraft when they get dinged while in use. XPS densities are similar to the PU foam used for traditional construction.

Surfcraft take a lot of punishment in waves (often equivalent to class 4-5 whitewater). Surfcraft are also exposed to rapidly changing temperature extremes (hot sun – beach & car racks – then straight into cool-cold water). As much as 50 F temperature differential within a few minutes (expansion and contraction). Pressure dings on the decks from heels on take-offs (foam crushing: minimum compressive strength). All of this magnifies problems with delamination.

Delamination is the big problem. Some builders claim no problem with XPS delaminating. Others report the XPS delams almost immediately. My observation has been that those who report instant delamination are using XPS with 15 psi min. comp. strength.

Some of those who report successful use of XPS swear by cleaning the (printed) surfaces of retail XPS with high purity denatured alcohol first, before doing any other surface work.

I found 3M 78 adhesive bonds XPS sheets well if you don't need to sand or hotwire bonded seams of foam. However, to get max bond strength, I had to let the bonded sheets cure for 2-3 days.

The following is some of the useful information I gleaned over the past several years:

Regarding strength for internal 90 degree joints, a fillet of epoxy/flocked cotton (flox) can be used as a fairly cost effective way to strengthen the fiberglassed internal surface of the joint. For a chemical bond, the epoxy-flox mix needs to be applied before the epoxy cures. Amine blush on epoxy cured in humid environments will affect bond between epoxy coats.

Regarding composite sandwich construction, an engineer who manufactured EPS surfboard blanks told me, “Fiberglass and other composite skins should be viewed as surfaces rather than part of the core. The composite skins are minimizing parallel surface movements relative to the core.”

Regarding stiffnes/flex, I played with building longboard skateboard and mounatinboard decks. Stiffness significantly affects performance. The critical lesson for me was, “Stiffness is directly proportional to the cube of thickness.”

Regarding bonding of materials, material surface energy is the determining factor. All compounds with surfaces have their own unique surface energy value (polyethylene = 32; polystyrene = 34; 6,6 nylon = 42; glass = 250-500; etc.). The take away is that epoxy adheres better with solid surfaces that have surface energy values equal to or greater than 45 dyne/cm.

Where I am going next with WPT perforation is orientation of perforation slits/cuts relative to the axes of flexing.

I have been determined to make retail XPS a viable core material for surfcraft. I am fairly confident I have found my answers. My next build, when weather warms, should be the final proof.
 
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#88
My pleasure ersatzknarf.
BTW some denatured alcohol (DNA) can contain denaturing agents that dissolve XPS (acetone, etc.). Be sure to check the MSDS of the DNA.
I have never tried DNA. For my last project, I tried isopropyl alcohol for wipe down, then let surfaces dry before further prepping the XPS surfaces.
It's always a good idea to try any new technique/material on a small XPS test panel before scaling up to your main project.
 
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#89
Hi all, all this info has been great and thanks. I started this thread a while back about glassing the corners and has now expanded with much more info. Now say after some more learning/reading I am starting to wonder about a steel frame with composite panels. Sort of like what Bliss Mobil does (if I could afford one that is what I would get). One of the main reasons is that I am now thinking of hanging a Yamaha TW200, spare tire, likely sand tracks and a couple of jerrycans for gasoline. The intended chassis is a 1017 AF (or cousin 1019, 1120, I am hopefully making a deal this coming week). I was concerned about a full composite body, or a Total Composites body and it would work. With the cage approach you could attach the lift to the top of the frame (I like the look of Bliss Mobiles setup for that also). With the composite approach I would guess it would all have to be built to attach at the truck chassis (and I am not sure how well that would work).
 
#90
Surfcraft take a lot of punishment in waves (often equivalent to class 4-5 whitewater). Surfcraft are also exposed to rapidly changing temperature extremes (hot sun – beach & car racks – then straight into cool-cold water). As much as 50 F temperature differential within a few minutes (expansion and contraction). Pressure dings on the decks from heels on take-offs (foam crushing: minimum compressive strength). All of this magnifies problems with delamination.

Delamination is the big problem. Some builders claim no problem with XPS delaminating. Others report the XPS delams almost immediately. My observation has been that those who report instant delamination are using XPS with 15 psi min. comp. strength.

Some of those who report successful use of XPS swear by cleaning the (printed) surfaces of retail XPS with high purity denatured alcohol first, before doing any other surface work.
All very good points. But using higher density XPS doesn't solve the issue of outgassing. There was a camper build on this site where the builder experienced delamination due to heat (first time the camper saw the sun). It was sanded (only) 60 psi XPS. Outgassing of XPS at elevated temperatures can cause this. I've heard of one surfboard builder who perforates the FG skin on his boards with tiny needles. But I suspect that delamination of this sort can be eliminated by ensuring a good bond.