I’m so glad you’re back! Thank you so much for doing this particular laminate sample. This is something I’m always thinking about doing and you saved me a bunch of trouble.😅
I built a couple of surfboards with XPS, wet layup e-glass and epoxy. I used a couple of techniques to encourage good skin bonding, like a row of 10-12 exacto blades to score grooves, and initially it was ok but they all delammed eventually. My understanding is that XPS has around 10 percent polyethylene added. This keeps it from sticking as it's extruded. It also keeps anything from actually chemically bonding to the foam, so physical bonding helps. Over time it seems to lose it's grip, perhaps because cycling slowly breaks all the weak surface bonds that initially stuck to the PE. Another issue is that it's closed-cell enough to trap air pockets that will expand with heat and grow with cycles. Too bad, that foam's physicals are really good. Thanks and the library is awesome!
Thank you for the information about XPS - I didn't know about the PE added or consider the trapped air expansion risk. I came off as pretty down on it in this video, but only because I was trying to get more from it than it can offer. If you're building super light stuff with little risk of impact - it can be great!
Very helpful. Echo Tom's comment, glad your back. I've used XPS only for the base core of plugs, easy to cut and stand on edge laminated with foam construction adhesive. For that purpose it's worked well and saved money. You're test confirmed my intuition regarding it's use as a core material. Thanks performing and recording the test. I suspect you saved at least a few folks some frustration.
It certainly has its place - even as a core if you can control peel and don't plan to have impacts. I still think there's something to the thin layers of higher density core on the faces to manage skin adhesion and impact resistance, but the whole sandwich is still limited by the weakness of bonding anything to the super low density XPS.
@@ExploreComposites I am thinking of make a truck camper roof with XPS foam, the plan is 60 PSI XPS + 2 layer of carbon fiber, with a 6.5" x 13" test piece, it can support 125lbs. Yes, I know the de delaminate issue, but the lightweight really attract me. Any suggestion for the pop up topper roof core?
I used XPS as a foam core in a few windsurfing boards. They were exceptionally light and lasted very well. I did use on of the denser grades. I would not hesitate in using this again. It certainly is worth considering for other uses, say a small dinghy / yacht tender. I would not use it for the main structure on a yacht, but for non critical parts, perhaps. Particularly if you were after good insulation, for the least cost
I haven't found an easy source for higher density XPS, but I bet it would work pretty well even at 2-3 pound density. Compression strength and peel-resistance is probably closely correlated with density. Hoping to try some out soon!
Thank you for making this video, I've been eyeballing some XPS foam sheets we have at home to repurpose into a lightweight sleeping platform for a vehicle. It's good to know that it probably won't work well, as that is a lot of cloth and resin to waste if it delaminates and/or gets damaged so easily.
As a structural flat panel, it definitely doesn't do so well. However, this is a method that's been used for more than a decade in the model airplane community with great success, although we typically are sanding the XPS into complex curved shapes (much stronger) and we have to make a lot of concession for ultimate strength to keep weight to an absolute minimum. That said, the 25psi XPS has made me fine electric jet models for years which easily exceed 150mph and have the structural integrity to pull out of a dive at that speed and straight back up. We also use carbon fiber tube to make strengthening spars, but still. That said, there's a TH-cam channel called ThinkFlight who's perfected a process with low density EPP foam, Kevlar fabric, and E6000 craft glue thinned out to nicely wet the fabric that makes a nearly indestructible airplane that bounces off almost anything.
Thank you for this! I would love to learn more about model aircraft building. Impacts seem to be the big issue but even surfboards make it work. Going to look into other low density foams and will check out EPP.
No problem! I always like to see new building techniques for just about anything, especially involving composites. A method that's worked pretty well for me, and makes planes that, while not indestructible, are very tough, but still very light, is to use only a single layer of 7gsm genuine Kevlar veil as the stressed skin over a built-up, shaped XPS fuselage. It still adds a lot of strength and stiffness while remaining very light,and transparent to radio frequency. But yeah, hot wire cutting the rough shape from an EPP billet, then sanding to final shape, then using a 2x2 twill ~3.5oz Kevlar with thinned E6000 makes a plane that can hit a telephone pole at 70mph and simply tumble to the ground with nothing more than scuffs and a broken propeller.@@ExploreComposites
Interesting! Yes, I had similar thoughts to those of guerrillaradio9953. The bottom line here- not all applications need the same results! Explore Composites is speaking more to those who are making serious structural components for boats, cars, RV's and such- so taking a hammer to his parts are like like simulating a hammer falling to the floor or something- a reasonable test- but when he was about to strike the finished board on the XPS side with a metal hammer, I almost screamed! Who hits a REAL airplane, let alone an ultralightweight model airplane with a metal hammer!!!! Many model airplanes these days are made of EPS (the ultra light white stuff packing foam is made of). That material is only 1/2 to 1/4 as strong as XPS, yet it works for many model airplanes with minimal bracing needed only in the most important locations. XPS is considered an UPGRADE compared to EPS in the model airplane world, and if you cover your XPS model airplane with just ONE layer of ANY normal bidirectional composite material- regardless of how thin it is, then you have improved it's strength and ruggedness enormously. When looking at this from a scientific/engineering loads and stresses perspective, the stresses in a model airplane are TINY compared to the stressed seen in a car, boat or RV application. You don't a model airplane to survive being stepped on hitting a wave at 60 MPH- but most of what is built in this TH-cam channel CAN take abuse on that order of magnitude. Last point- model airplanes ARE strong enough to surviving some bad landings- but only because they are so light.
A big issue with XPS foam is that it releases gas when pressed/crushed. That is the reason why some surfboard manufacturers that uses XPS as foam core have to drill holes every inch or so through the fiberglass into the foam to allow the gas to come out and avoid delimitation (e.g. XTR technology). Thankfully, XPS been closed cell, water won't get in. Unlike EPS (open cells), adding a Gortex valve in XPS surfboard won't help since there is no path for the gas to come out.
Precision Fabrics Group (www.precisionfabrics.com) might get you samples. I am pretty sure Composites One distributes some of these heavy veils too. I originally learned about them as part of testing for co-infused or pre-cured skin coats to help with cosmetics where there were some pretty specific issues that made typical methods less appealing. There are fluffier spun polyester print-blockers that build more thickness (but with more heavy resin) and are more drapeable - Lantor makes some. This PFG stuff isn't super stretchy.
Sanding the surface of the xps would help. In the case of pvc foam, it has a closed cell structure, but in the process of cutting the surface, the cells on the surface become open, increasing the bonding force and reducing the peeling phenomenon.
Thank you. This is just the video I have been looking for. Took about a month to find this video but it answered my question about making a boat out of purple foam. :)
Sorry for left so many comments under different threads. I am near pull the trigger to source XPS + carbon fiber for my popup topper project, but little bit hesitate after read all your reply. Previously I have done test with XPS 15 PSI, and Nomex 3/8" thickness 1/8" cell, both performance can meet my requirement. But Since I can easily find 2" XPS with R10 in hand, but the maximum Nomex I can find is 1" which lead my head on XPS 60PSI version. Or maybe I can use two layer or Nomex core? I am totally new in this area, any suggestion are welcome.
Maybe, but it wouldn't be very strong and would dent easily. You could certainly fiberglass over an outdoor countertop more heavily - or lightly if the underlying structure is plywood or something strong. Plenty of boats have decks made out of plywood with fiberglass (ideally in epoxy) over - works great!
@@ExploreComposites yea im trying to find a substrate to do a outdoor kitchen on..the epoxy and top coat i have that figured it out..tricoya is 385$ waterproof my wow that price for a 4x10 im almost thinking solid surface/corian
I don't know - never used it. Probably an adequate option compared to lamination directly on the foam. Maybe a foaming gap filling adhesive would be good? The denser layer was just there to see if it prevented denting: yes, or improved adhesion: kinda but not between the two foams.
I'm glad you posted this video. I've seen some videos where cheap, DYI cabinets for van conversions were made using XPS. After seeing this, I'm glad I didn't try it.
Well, with thicker skins it might work ok, but there are probably better ways to do cheap cabinets! For things that must be super light, maybe its worth the trouble?
I’d imagine it would help. Here the foam just separated right at the surface leaving a pink fuzz on the cured skin inner surface. Somewhere I saw a datasheet for a bunch of densities of the Foamular NGX that included compressive strength.
@@ExploreComposites The XPS in your video should be Foamular 150 (15 PSI) version, they have 250/400/600/1000 which mapping to 25/40/60/100 PSI version, higher PSI means more density. I found a local dealer with 60PSI in stock, will try
Strength and stiffness are very different - and sandwich panel core thickness, density and face-sheet properties vary a lot! This panel is very thick, but core density (and compressive/shear strength) is very low. This is a very strange corner of the options available so it is interesting but only useful for very light and unloaded structures. Plywood and 800gsm biax are in a much more well-behaved (and heavy) area of composite skin/core options.
XPS foam is a polystyrene foam. Epoxy as we all know is exothermic meaning that it generates heat. Foam and heat do not mix . That being said. There is a way that you could’ve done it if you would’ve used a penetrating epoxy with a slow hardening on the foam And put it in your vacuum sealer and basically allowed that to cure with just the epoxy, sanded it, and then add your other substrate with your fiberglass, obviously sanding to create a mechanical bond, you would’ve not had delamination. It would’ve been a solid structure way more solid than you did.
This is interesting - the way it failed looked very much like failure of the foam, but if your penetrating epoxy could get a better (deeper) grip, maybe it would be tougher. Usually penetrating epoxies have very low viscosity and that helps make them penetrate - do you think this would help here? Thanks!
@@ExploreComposites FINNFOAM has been used to make at least 2 boats, believe deeper penetration of epoxy helped but really vacuum infusing it is the way to go, only that would cause it to deform under pressure.
XPS foam has a coating on it due to the manufacturing process. That coating should be removed via sanding or hot wire so the epoxy will form a good bond.
Thanks for the info - that makes sense. I will have to experiment with it more. I wonder if the hot-wire process itself makes for an improved bond where the melting has happened?
I use xps and eps in surfboard building with 3-5mm pvc foam sandwich or 0,6mm wood veneer ....u can have a much better bond by adding some microballon-epoxy filler on the xps foam :)
Thats interesting! I was kind of thinking surfboard here - so you use the PVC foam or veneer to improve surface impact resistance? Or skin adhesion? EPS I can totally see benefitting from the micro balloons - does it make as much difference with the finer grained XPS?
How do you explain successful test by easy composites when xps is wrapped in carbon. Here is the 2nd video where they are testing for strength. th-cam.com/video/FFi2H_PC7hw/w-d-xo.html
The XPS they are using is 33kg/m^3 which is about 2lb/cubic foot - compared to the pink stuff in this video which is about 1.3lb/cubic foot - so it should be much better in all ways (except weight) as a core. Another key difference is that the airfoil is actually a tube, so some of the shear is carried by the skins that wrap (leading) and connect (trailing) edges. The core is strong enough in compression that the top skin fails first, which may be more of a uniform loading on the compression side thing. You could certainly do the same process with the pink foam, and it would work fine - but would be a little lighter and substantially less rugged than the one in the Easy Composites video. The big issue I saw is the minimal peel strength of the skin to core bond - with the section totally wrapped, this isn't an issue as much. If you can avoid peeling situations, the core works pretty well for its density - which is very very low as cores go. Overall the method they show is a great way to get a mold-less airfoil with very little work. It could certainly be tweaked with different core densities and laminates to perform even better - but it's pretty impressive as is!
@@ExploreComposites I wish you'd skinned both sides with cloth and not just used a veil on one of them. During your final strength testing it looks like the veil fractured on the compression side as the foam compressed, and it's not clear which happened first. It's unfortunate that neither side of your panel had a strong reinforcement directly onto the foam because you weren't able to evaluate the compressive properties of that more-typical construction. That Foamular project board is rated either 15 or 25 PSI in compression, and neither Home Depot nor Owens Corning make it clear which. It might be possible that those 2x2 panels are extruded from end-of-batch foam used in other products, and could vary between the two ratings, but I'm just speculating here as I cannot see any other reason for OC to not just state which it is. Regardless, that board is strong enough to stand on without reinforcement (wearing flat shoes), and with a suitably stiff surface reinforcement to spread the load it should be fine in most applications. Remember, the main purpose of core foams is to separate the compression and tension reinforcement layers to increase bending strength and stiffness. If extra impact resistance is needed, an aramid layer might be appropriate. I had tested this foam board with a single ~200gsm glass cloth skin on each side and it was pretty stiff and strong. I used the surprisingly elegant "homemade prepreg" method of wetting out glass by rolling it on a flat surface between two layers of polyethylene, then using scissors to cut out reinforcement panels before removing the poly. As others have found, my resulting test panel will delaminate fairly easily despite having sanded the foam beforehand. I can just create an indentation with my thumb, but only just and with a lot of force. I think a second glass layer would prevent that, so I'm fairly confident about the foam's compressive strength. Upon bend load-testing, the failure mode is delamination of the compression side. That delamination is audible as the glass pops away from the foam. Eventually a crease occurs along the line where most delamination has occurred at the axis of most stress. Attaining a good bond strength will be the key to using this foam. It remains interesting to many for its low cost and easy availability. I read where someone had performed a series of experiments examining the bond strength with unexpected results. Sanding, drilling and blade-scoring were not very effective. Apparently their best result was obtained by scratching the surface with a fine wire pet fur brush. They claimed that after doing that the foam would tear internally before the bond failed. I have yet to find time to replicate that, but if true, it could be exciting. I'd like to make lightweight composite baseboards for a model railway. Given the size, pricing is definitely a concern. I think XPS with 2 layers of glass on each side might be an economically viable solution. Ideally a one-step infusion process would be achievable, but if that doesn't work, a two step process of bonding finished skins to the foam would be ok too. (That might help with both bonding and edge-crush). Owens Corning also make an industrial insulation product, Foamglas, which is designed to be used in more demanding and structural applications, including under cryogenic tanks, or to insulate direct-buried pipes. It's available in a board format with a glass fleece facing to aid bonding. It looks interesting, but I suspect availability and cost might take it out of consideration.
I used 2-inch thick 2# Dow Foamular to build a mold for a 48" long x 8" radius fairing half..well, to mold 2 fairing halves. That foam is a nightmare to use, never again! The deal breaker is that this foam is not rigid. It's spongy! Because it's rigid, filling holes and then sanding the filler down to the foam surface does not work. The hardened filler moves downward when the sandpaper contacts it, and the sandpaper ends up sanding the surrounding foam instead. Stop sanding, and the hard filler pops back up, above the surrounding foam! Like others, I've used this foam to make hydrofoil boards, for which it does work well. Garbage for making tooling though!
Yes! Been there, struggled with that. It's the worst. I keep coming back to wood (but mostly MDF) as about the ideal cheap tooling material. Harder to shape, but stable (ish) and uniform.
@@ExploreComposites Yeah, I've built MDF tooling before. Glued up a large block, CNC machined it, sanded, then coated, sanded and polished polyester tooling resin (duratec). Still, the hairs from the MDF prevented part release. Had to demold the parts using a hammer and chisel. Every time, lol!
I’m so glad you’re back! Thank you so much for doing this particular laminate sample. This is something I’m always thinking about doing and you saved me a bunch of trouble.😅
I built a couple of surfboards with XPS, wet layup e-glass and epoxy. I used a couple of techniques to encourage good skin bonding, like a row of 10-12 exacto blades to score grooves, and initially it was ok but they all delammed eventually. My understanding is that XPS has around 10 percent polyethylene added. This keeps it from sticking as it's extruded. It also keeps anything from actually chemically bonding to the foam, so physical bonding helps. Over time it seems to lose it's grip, perhaps because cycling slowly breaks all the weak surface bonds that initially stuck to the PE. Another issue is that it's closed-cell enough to trap air pockets that will expand with heat and grow with cycles. Too bad, that foam's physicals are really good. Thanks and the library is awesome!
Thank you for the information about XPS - I didn't know about the PE added or consider the trapped air expansion risk. I came off as pretty down on it in this video, but only because I was trying to get more from it than it can offer. If you're building super light stuff with little risk of impact - it can be great!
Very helpful. Echo Tom's comment, glad your back. I've used XPS only for the base core of plugs, easy to cut and stand on edge laminated with foam construction adhesive. For that purpose it's worked well and saved money. You're test confirmed my intuition regarding it's use as a core material. Thanks performing and recording the test. I suspect you saved at least a few folks some frustration.
It certainly has its place - even as a core if you can control peel and don't plan to have impacts. I still think there's something to the thin layers of higher density core on the faces to manage skin adhesion and impact resistance, but the whole sandwich is still limited by the weakness of bonding anything to the super low density XPS.
@@ExploreComposites I am thinking of make a truck camper roof with XPS foam, the plan is 60 PSI XPS + 2 layer of carbon fiber, with a 6.5" x 13" test piece, it can support 125lbs. Yes, I know the de delaminate issue, but the lightweight really attract me. Any suggestion for the pop up topper roof core?
I used XPS as a foam core in a few windsurfing boards. They were exceptionally light and lasted very well. I did use on of the denser grades. I would not hesitate in using this again.
It certainly is worth considering for other uses, say a small dinghy / yacht tender. I would not use it for the main structure on a yacht, but for non critical parts, perhaps. Particularly if you were after good insulation, for the least cost
I haven't found an easy source for higher density XPS, but I bet it would work pretty well even at 2-3 pound density. Compression strength and peel-resistance is probably closely correlated with density. Hoping to try some out soon!
Thank you for making this video, I've been eyeballing some XPS foam sheets we have at home to repurpose into a lightweight sleeping platform for a vehicle. It's good to know that it probably won't work well, as that is a lot of cloth and resin to waste if it delaminates and/or gets damaged so easily.
As a structural flat panel, it definitely doesn't do so well. However, this is a method that's been used for more than a decade in the model airplane community with great success, although we typically are sanding the XPS into complex curved shapes (much stronger) and we have to make a lot of concession for ultimate strength to keep weight to an absolute minimum. That said, the 25psi XPS has made me fine electric jet models for years which easily exceed 150mph and have the structural integrity to pull out of a dive at that speed and straight back up. We also use carbon fiber tube to make strengthening spars, but still.
That said, there's a TH-cam channel called ThinkFlight who's perfected a process with low density EPP foam, Kevlar fabric, and E6000 craft glue thinned out to nicely wet the fabric that makes a nearly indestructible airplane that bounces off almost anything.
Thank you for this! I would love to learn more about model aircraft building. Impacts seem to be the big issue but even surfboards make it work. Going to look into other low density foams and will check out EPP.
No problem! I always like to see new building techniques for just about anything, especially involving composites. A method that's worked pretty well for me, and makes planes that, while not indestructible, are very tough, but still very light, is to use only a single layer of 7gsm genuine Kevlar veil as the stressed skin over a built-up, shaped XPS fuselage. It still adds a lot of strength and stiffness while remaining very light,and transparent to radio frequency. But yeah, hot wire cutting the rough shape from an EPP billet, then sanding to final shape, then using a 2x2 twill ~3.5oz Kevlar with thinned E6000 makes a plane that can hit a telephone pole at 70mph and simply tumble to the ground with nothing more than scuffs and a broken propeller.@@ExploreComposites
Interesting! Yes, I had similar thoughts to those of guerrillaradio9953. The bottom line here- not all applications need the same results! Explore Composites is speaking more to those who are making serious structural components for boats, cars, RV's and such- so taking a hammer to his parts are like like simulating a hammer falling to the floor or something- a reasonable test- but when he was about to strike the finished board on the XPS side with a metal hammer, I almost screamed! Who hits a REAL airplane, let alone an ultralightweight model airplane with a metal hammer!!!! Many model airplanes these days are made of EPS (the ultra light white stuff packing foam is made of). That material is only 1/2 to 1/4 as strong as XPS, yet it works for many model airplanes with minimal bracing needed only in the most important locations. XPS is considered an UPGRADE compared to EPS in the model airplane world, and if you cover your XPS model airplane with just ONE layer of ANY normal bidirectional composite material- regardless of how thin it is, then you have improved it's strength and ruggedness enormously. When looking at this from a scientific/engineering loads and stresses perspective, the stresses in a model airplane are TINY compared to the stressed seen in a car, boat or RV application. You don't a model airplane to survive being stepped on hitting a wave at 60 MPH- but most of what is built in this TH-cam channel CAN take abuse on that order of magnitude. Last point- model airplanes ARE strong enough to surviving some bad landings- but only because they are so light.
A big issue with XPS foam is that it releases gas when pressed/crushed. That is the reason why some surfboard manufacturers that uses XPS as foam core have to drill holes every inch or so through the fiberglass into the foam to allow the gas to come out and avoid delimitation (e.g. XTR technology). Thankfully, XPS been closed cell, water won't get in. Unlike EPS (open cells), adding a Gortex valve in XPS surfboard won't help since there is no path for the gas to come out.
Wow! that print blocker looks very nice, do you have a recommended distributer or somewhere you think I could grab a sample? thanks Chris
Precision Fabrics Group (www.precisionfabrics.com) might get you samples. I am pretty sure Composites One distributes some of these heavy veils too. I originally learned about them as part of testing for co-infused or pre-cured skin coats to help with cosmetics where there were some pretty specific issues that made typical methods less appealing. There are fluffier spun polyester print-blockers that build more thickness (but with more heavy resin) and are more drapeable - Lantor makes some. This PFG stuff isn't super stretchy.
I did a similar sample with foam and carbon. It was very rigid due to the carbon, but it would still crush or delaminate...
Sanding the surface of the xps would help. In the case of pvc foam, it has a closed cell structure, but in the process of cutting the surface, the cells on the surface become open, increasing the bonding force and reducing the peeling phenomenon.
I totally forgot to mention it but I did sand with 120g before cutting in the slices on both faces of the XPS… oops!
Thank you. This is just the video I have been looking for. Took about a month to find this video but it answered my question about making a boat out of purple foam. :)
Turns out we CAN have nice things, and Explore Composites is the nice things
Sorry for left so many comments under different threads. I am near pull the trigger to source XPS + carbon fiber for my popup topper project, but little bit hesitate after read all your reply. Previously I have done test with XPS 15 PSI, and Nomex 3/8" thickness 1/8" cell, both performance can meet my requirement. But Since I can easily find 2" XPS with R10 in hand, but the maximum Nomex I can find is 1" which lead my head on XPS 60PSI version. Or maybe I can use two layer or Nomex core?
I am totally new in this area, any suggestion are welcome.
could i use this method to build a outdoor countertop
Maybe, but it wouldn't be very strong and would dent easily. You could certainly fiberglass over an outdoor countertop more heavily - or lightly if the underlying structure is plywood or something strong. Plenty of boats have decks made out of plywood with fiberglass (ideally in epoxy) over - works great!
@@ExploreComposites yea im trying to find a substrate to do a outdoor kitchen on..the epoxy and top coat i have that figured it out..tricoya is 385$ waterproof my wow that price for a 4x10 im almost thinking solid surface/corian
Interesting experiment. What do you think about Filon paneling on top of XPS? Would you still need to have another denser layer underneath?
I don't know - never used it. Probably an adequate option compared to lamination directly on the foam. Maybe a foaming gap filling adhesive would be good? The denser layer was just there to see if it prevented denting: yes, or improved adhesion: kinda but not between the two foams.
I'm glad you posted this video. I've seen some videos where cheap, DYI cabinets for van conversions were made using XPS. After seeing this, I'm glad I didn't try it.
Well, with thicker skins it might work ok, but there are probably better ways to do cheap cabinets! For things that must be super light, maybe its worth the trouble?
@@ExploreComposites Exactly!
Do you think the higher density versions of Foamular would provide better performance?
I’d imagine it would help. Here the foam just separated right at the surface leaving a pink fuzz on the cured skin inner surface. Somewhere I saw a datasheet for a bunch of densities of the Foamular NGX that included compressive strength.
@@ExploreComposites The XPS in your video should be Foamular 150 (15 PSI) version, they have 250/400/600/1000 which mapping to 25/40/60/100 PSI version, higher PSI means more density. I found a local dealer with 60PSI in stock, will try
What about 12mm plywood with 800grm2 4545 double sided, how ve can same strength with using 20 or 30mm core? How much fiber ve need
Strength and stiffness are very different - and sandwich panel core thickness, density and face-sheet properties vary a lot! This panel is very thick, but core density (and compressive/shear strength) is very low. This is a very strange corner of the options available so it is interesting but only useful for very light and unloaded structures. Plywood and 800gsm biax are in a much more well-behaved (and heavy) area of composite skin/core options.
XPS foam is a polystyrene foam. Epoxy as we all know is exothermic meaning that it generates heat. Foam and heat do not mix . That being said. There is a way that you could’ve done it if you would’ve used a penetrating epoxy with a slow hardening on the foam And put it in your vacuum sealer and basically allowed that to cure with just the epoxy, sanded it, and then add your other substrate with your fiberglass, obviously sanding to create a mechanical bond, you would’ve not had delamination. It would’ve been a solid structure way more solid than you did.
This is interesting - the way it failed looked very much like failure of the foam, but if your penetrating epoxy could get a better (deeper) grip, maybe it would be tougher. Usually penetrating epoxies have very low viscosity and that helps make them penetrate - do you think this would help here? Thanks!
@@ExploreComposites FINNFOAM has been used to make at least 2 boats, believe deeper penetration of epoxy helped but really vacuum infusing it is the way to go, only that would cause it to deform under pressure.
Thank you
It's not a failed experiment unless you don't learn anything.
XPS foam has a coating on it due to the manufacturing process. That coating should be removed via sanding or hot wire so the epoxy will form a good bond.
Thanks for the info - that makes sense. I will have to experiment with it more. I wonder if the hot-wire process itself makes for an improved bond where the melting has happened?
I use xps and eps in surfboard building with 3-5mm pvc foam sandwich or 0,6mm wood veneer ....u can have a much better bond by adding some microballon-epoxy filler on the xps foam :)
Thats interesting! I was kind of thinking surfboard here - so you use the PVC foam or veneer to improve surface impact resistance? Or skin adhesion?
EPS I can totally see benefitting from the micro balloons - does it make as much difference with the finer grained XPS?
But you do use a pressure valve in the foam?
@@ExploreComposites impact general
How do you explain successful test by easy composites when xps is wrapped in carbon. Here is the 2nd video where they are testing for strength. th-cam.com/video/FFi2H_PC7hw/w-d-xo.html
The XPS they are using is 33kg/m^3 which is about 2lb/cubic foot - compared to the pink stuff in this video which is about 1.3lb/cubic foot - so it should be much better in all ways (except weight) as a core. Another key difference is that the airfoil is actually a tube, so some of the shear is carried by the skins that wrap (leading) and connect (trailing) edges. The core is strong enough in compression that the top skin fails first, which may be more of a uniform loading on the compression side thing.
You could certainly do the same process with the pink foam, and it would work fine - but would be a little lighter and substantially less rugged than the one in the Easy Composites video. The big issue I saw is the minimal peel strength of the skin to core bond - with the section totally wrapped, this isn't an issue as much. If you can avoid peeling situations, the core works pretty well for its density - which is very very low as cores go. Overall the method they show is a great way to get a mold-less airfoil with very little work. It could certainly be tweaked with different core densities and laminates to perform even better - but it's pretty impressive as is!
@@ExploreComposites
Thanks
@@ExploreComposites I wish you'd skinned both sides with cloth and not just used a veil on one of them. During your final strength testing it looks like the veil fractured on the compression side as the foam compressed, and it's not clear which happened first. It's unfortunate that neither side of your panel had a strong reinforcement directly onto the foam because you weren't able to evaluate the compressive properties of that more-typical construction. That Foamular project board is rated either 15 or 25 PSI in compression, and neither Home Depot nor Owens Corning make it clear which. It might be possible that those 2x2 panels are extruded from end-of-batch foam used in other products, and could vary between the two ratings, but I'm just speculating here as I cannot see any other reason for OC to not just state which it is. Regardless, that board is strong enough to stand on without reinforcement (wearing flat shoes), and with a suitably stiff surface reinforcement to spread the load it should be fine in most applications. Remember, the main purpose of core foams is to separate the compression and tension reinforcement layers to increase bending strength and stiffness. If extra impact resistance is needed, an aramid layer might be appropriate.
I had tested this foam board with a single ~200gsm glass cloth skin on each side and it was pretty stiff and strong. I used the surprisingly elegant "homemade prepreg" method of wetting out glass by rolling it on a flat surface between two layers of polyethylene, then using scissors to cut out reinforcement panels before removing the poly. As others have found, my resulting test panel will delaminate fairly easily despite having sanded the foam beforehand. I can just create an indentation with my thumb, but only just and with a lot of force. I think a second glass layer would prevent that, so I'm fairly confident about the foam's compressive strength. Upon bend load-testing, the failure mode is delamination of the compression side. That delamination is audible as the glass pops away from the foam. Eventually a crease occurs along the line where most delamination has occurred at the axis of most stress.
Attaining a good bond strength will be the key to using this foam. It remains interesting to many for its low cost and easy availability. I read where someone had performed a series of experiments examining the bond strength with unexpected results. Sanding, drilling and blade-scoring were not very effective. Apparently their best result was obtained by scratching the surface with a fine wire pet fur brush. They claimed that after doing that the foam would tear internally before the bond failed. I have yet to find time to replicate that, but if true, it could be exciting. I'd like to make lightweight composite baseboards for a model railway. Given the size, pricing is definitely a concern. I think XPS with 2 layers of glass on each side might be an economically viable solution. Ideally a one-step infusion process would be achievable, but if that doesn't work, a two step process of bonding finished skins to the foam would be ok too. (That might help with both bonding and edge-crush).
Owens Corning also make an industrial insulation product, Foamglas, which is designed to be used in more demanding and structural applications, including under cryogenic tanks, or to insulate direct-buried pipes. It's available in a board format with a glass fleece facing to aid bonding. It looks interesting, but I suspect availability and cost might take it out of consideration.
I used 2-inch thick 2# Dow Foamular to build a mold for a 48" long x 8" radius fairing half..well, to mold 2 fairing halves. That foam is a nightmare to use, never again! The deal breaker is that this foam is not rigid. It's spongy! Because it's rigid, filling holes and then sanding the filler down to the foam surface does not work. The hardened filler moves downward when the sandpaper contacts it, and the sandpaper ends up sanding the surrounding foam instead. Stop sanding, and the hard filler pops back up, above the surrounding foam!
Like others, I've used this foam to make hydrofoil boards, for which it does work well. Garbage for making tooling though!
Yes! Been there, struggled with that. It's the worst. I keep coming back to wood (but mostly MDF) as about the ideal cheap tooling material. Harder to shape, but stable (ish) and uniform.
@@ExploreComposites Yeah, I've built MDF tooling before. Glued up a large block, CNC machined it, sanded, then coated, sanded and polished polyester tooling resin (duratec). Still, the hairs from the MDF prevented part release. Had to demold the parts using a hammer and chisel. Every time, lol!
Note to self. Don’t use this garbage as a core material in a boat lol