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Hi everyone, I have been researching core materials and found myself on the DIAB website and was surprised as to how many different kinds they offer. I am waiting to hear back from them, but wanted to ask when you guys use one material over another, preferences, thoughts on the different materials. I hear balsa wood still has one of the highest strength/weight with great compression strength but doesn't conform to complex shape, is more moisture absorbent and usually thicker than foams available. FWIW, it was used in production c6 floorboards. I see the soric SF is unique in that it's channels that make a resin/honeycomb structure when used. How does it compare to the Divinyl foams? Diab had 12 different types of Divinyl foam( PES, PET, IPN), Sintactic foams and I've seen multiple weight/density pour urethane foams. Honeycombs are on the expensive side, usually made of Nomex or aluminum. With how strong laminates can be made with soric mat and foams, when would you choose honeycomb? Is it when Higher impact strength is needed or is it when weight is the number 1 concern? I would think resin filling the honeycomb would be a concern, unless using pre-preg? Any thoughts?
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Realistically, budget is probably the main consideration. Honeycombs offer the best compressive strength and stiffness of any core material. It's very low density, and performs very well in 'hostile' environments (resists corrosion, moisture, heat, etc). Aluminium honeycombs can be very useful for impact absorption structures as they disperse a lot of energy. On the other hand, honeycombs are quite expensive, especially aramid paper honeycombs. What makes them even more expensive is the fact that they are quite limited in their processing; either you use more expensive pre-pregs, or you create multiple skins prior to bonding the honeycomb in, effectively doubling or even tripling the manufacturing process, which costs more in labour time. You could obviously do it in one shot with wet-lay, but you lose the ability to absorb as much excess resin, resulting in lower performance. Obviously resin infusion in one shot is totally out of the question. There's also the fact that due to the very limited surface area for bonding the cells to the laminate, and obviously the bond stength is crucial to the performance, honeycombs are generally only used with epoxy resins and adhesives, which are again more expensive. End-grain balsa is still a good core material, however it does absorb resin unless it's sealed and it isn't very good in hostile environments (moisture, not fire-retardant, etc). It also isn't cheap compared to other options. Foam is a pretty good middle ground, and really the options available make it such a versatile option. You can essentially find a suitable foam for whatever manufacturing process you are wanting to use, it's lower density than balsa, it has better environmental performance, it is compatible with all resin systems, it's comparatively cheap... To answer your question, I'd say honeycomb cores are chosen over foams when the ultimate performance is needed and the budget allows for it. In applications like aerospace and F1, obviously the application demands are sufficient that budget is less of a concern. Whereas marine and general automotive applications, performance is secondary to expense.
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I thought so about the homeycomb, Any preference, insight on which foam/soric is better than the other for a certain situation?
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Just got off Airex website, has nice/detail data sheets on their foams,(11 different types). The PX style is interesting, has a continuous fiberglass strain distributed throughout the urethane foam.
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There's so many types of foam available, again I think it depends on the application. I'm not personally a huge fan of Soric, it's heavy. I prefer Corecork over Soric, but Soric does have its benefits as well. I also like 3D PET core, but only for low stress applications. PET foam under stress will shear from itself, so for high stress applications I use H80 Divinycell, drilled and scored myself for infusion. Those are the cores I use the most.
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Hanaldo, thanks for your insight and the "corecork" material recommendation. I haven't seen that material listed on any supply sites before. Went to the corematerials site( not too far from me), had a nice material/strength comparison chart(attached). I have been checking out the grurit site. I also found some formula's /reading material... "food for thought" for us newbie's/ info. junkies- http://www.hexcel.com/Resources/DataSheets/Brochure-Data-Sheets/Honeycomb_Sandwich_Design_Technology.pdf
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Found core comparison graphs in a book I'm reading thought I'd post them. I think for most of us the shear strength is the most important?
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