{"id":651,"date":"2026-10-29T14:15:59","date_gmt":"2026-10-29T06:15:59","guid":{"rendered":"http:\/\/www.dipobisnis.com\/blog\/?p=651"},"modified":"2026-10-29T14:15:59","modified_gmt":"2026-10-29T06:15:59","slug":"what-is-the-moisture-absorption-of-carbon-fabric-4c73-f397df","status":"publish","type":"post","link":"http:\/\/www.dipobisnis.com\/blog\/2026\/10\/29\/what-is-the-moisture-absorption-of-carbon-fabric-4c73-f397df\/","title":{"rendered":"What is the moisture absorption of Carbon Fabric?"},"content":{"rendered":"

Hey there, if you\u2019ve ever worked with carbon fabric for anything from aerospace parts to hobbyist race car builds, you\u2019ve probably wondered why your stored rolls feel damp out of nowhere, or why a part you just bonded with epoxy didn\u2019t cure right. That\u2019s not you being clumsy\u2014that\u2019s carbon fabric\u2019s moisture absorption at play, and as a carbon fabric supplier who\u2019s talked through this with hundreds of customers over the years, I\u2019m here to break it down like I do when I\u2019m on the phone with someone panicking mid-project. Carbon Fabric<\/a><\/p>\n

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First, let\u2019s cut the jargon. Carbon fabric isn\u2019t just plain carbon fibers woven into a cloth\u2014each fiber is basically a long string of carbon atoms, right? But those atoms aren\u2019t perfectly smooth. They have tiny, microscopic gaps, and the surface of every fiber has functional groups (think little chemical \u201csticky spots\u201d) that love water. Unlike metal, which repels water, or some plastics that don\u2019t hold it, carbon\u2019s just the opposite. That\u2019s the core of its moisture absorption, and it\u2019s way more common than you might think.<\/p>\n

Now, how much water are we actually talking about? I get questions all the time: \u201cIs this a big problem, or just a little nuisance?\u201d Let\u2019s throw out the basic numbers I share with new clients: standard carbon fabric (the kind you use for most general manufacturing, like plain-twill or unidirectional) absorbs between 0.2% and 0.5% of its dry weight in water. Wait, that sounds small, but let\u2019s do the math: if you have a 10kg roll of carbon fabric, that\u2019s 20 to 50 grams of water. That\u2019s roughly 1 to 2 ounces, and when you\u2019re mixing epoxy that needs exact ratios (a lot of epoxies cure poorly if there\u2019s even a tiny amount of water disrupting the chemical reaction), that tiny bit can turn into a botched part fast. I\u2019ve seen a customer toss a $2k pre-preg layup because they stored their fabric in a damp garage and missed that 0.3% moisture\u2014they thought it was their epoxy, turns out it was just the fabric holding water.<\/p>\n

Here\u2019s the thing about how it absorbs too: it\u2019s not like a sponge soaking up a big puddle. Carbon fabric absorbs moisture gradually, based on humidity and temperature. If you store your fabric in a space with 60%+ relative humidity (that\u2019s like most basements, or a garage in the summer) for more than a week, it\u2019ll start picking up moisture. Warmer air holds more water, so a 70\u00b0F room at 70% humidity will get your fabric wet faster than a 50\u00b0F room at the same humidity. Even a roll that\u2019s sealed in plastic can get moisture if the plastic has a tiny pinhole, or if you open it in a humid room and don\u2019t re-seal it right away. That\u2019s another mistake I see all the time: people think \u201csealed is sealed\u201d but if you\u2019ve ever left a bag of chips open in a humid kitchen, you know how that goes. Same idea here.<\/p>\n

Now, is all carbon fabric the same when it comes to moisture absorption? Nope, that\u2019s why it matters where you get your fabric from (hint: that\u2019s where I come in). There are two main types: PAN-based carbon fabric (the most common, made from polyacrylonitrile fibers) and pitch-based (made from petroleum pitch). PAN-based fabric usually has more of those surface functional groups, so it absorbs more moisture\u2014like 0.3 to 0.5%. Pitch-based is a little smoother, so it\u2019s around 0.2 to 0.3%, but it\u2019s way more expensive, so most hobbyists and general manufacturers don\u2019t bother with it. Then there\u2019s surface treatment: some fabric gets a sizing (a thin coating to protect fibers during weaving) that\u2019s hydrophobic. Wait, that\u2019s a game-changer. If you buy fabric with a proprietary hydrophobic sizing (I work with a mill that adds a thin silicon-based sizing that doesn\u2019t mess with bonding), that moisture absorption drops to like 0.1% max. That\u2019s a huge difference. I always tell customers to ask their supplier about sizing\u2014if they say \u201cit\u2019s standard sizing,\u201d that might not be enough for outdoor or aerospace parts. If they can say it\u2019s a moisture-resistant sizing, that\u2019s the stuff you want.<\/p>\n

So what\u2019s the big deal if it does absorb moisture? Let\u2019s cover the common issues, because that\u2019s why every customer needs to care. First, epoxy curing: like I mentioned, water disrupts epoxy\u2019s cross-linking reaction. That makes the part weaker, more brittle, and way more likely to crack. For a race car part, that\u2019s dangerous. For a custom kayak hull, that\u2019s a flaw you\u2019ll feel after the first use. Second, delamination: if you\u2019re using multiple layers of fabric, trapped moisture between layers will turn into voids when it evaporates during curing. Voids are empty spaces that weaken the whole structure\u2014something as small as a void can cut a part\u2019s strength by 10-15% easily. Third, weight gain: if you\u2019re making a part where weight is critical (drones, bikes, robotics), that extra 0.5% water might not sound like much, but on a 1kg drone frame, that\u2019s 5 grams\u2014enough to make it less efficient, drain the battery faster, or even throw off the balance. I once had a drone builder come to me because his quad kept crashing mid-flight; he\u2019d stored his fabric in his workshop, which hit 80% humidity in the summer, and the extra moisture made the frame heavier and unbalanced.<\/p>\n

Now, can you reverse it? Yes, but not just leaving it out to dry. I see people do that all the time\u2014they throw their damp fabric on a workbench and leave it for a day, thinking it\u2019ll be fine. But carbon fabric\u2019s moisture is trapped in those microscopic fiber gaps, so surface drying takes a long time. The right way to dry it is low-temperature heat: 100-120\u00b0F (38-49\u00b0C) for 2-4 hours. That evaporates the trapped moisture without damaging the fibers or the sizing. I always tell customers not to go higher than 140\u00b0F\u2014too hot can break down the fiber\u2019s structure, or melt the sizing, which ruins the fabric\u2019s bonding properties. If you\u2019re using pre-preg fabric (carbon fabric already infused with epoxy), you can\u2019t really dry it once it\u2019s damp, because pre-preg has a shelf life, and moisture will make it cure prematurely or go bad before you use it. That\u2019s why pre-preg is almost always shipped and stored in vacuum-sealed bags in a cool place\u2014no exceptions.<\/p>\n

Wait, let\u2019s address a common myth I hear: \u201cIf carbon fabric is so good at holding moisture, why don\u2019t they make waterproof fabric out of it?\u201d Oh, that\u2019s a great question. Carbon fibers themselves are hydrophilic (water-loving), but when you weave them into fabric, you can add a coating, like Teflon, that makes the whole thing waterproof. But that coating is on the outside of the fabric, not the fibers themselves. The fibers still have those sticky spots, so if you cut the fabric and expose the raw fibers, those spots will still absorb moisture. That\u2019s why waterproof carbon fabric isn\u2019t the same as \u201cnon-moisture-absorbing\u201d carbon fabric\u2014totally different things. I explain that to people all the time, because they mix the two up.<\/p>\n

So, what can you do to prevent moisture absorption in the first place? This is stuff I share with every customer, because it\u2019s way easier than fixing a damp roll. First, store your fabric in a cool, dry place\u2014aim for under 50% relative humidity, and between 60-70\u00b0F. If your workshop is damp, get a dehumidifier. Second, re-seal rolls immediately after opening: use airtight plastic bags with desiccant packets (the little silica gel packs you get with electronics, those work perfect). I always tell customers not to throw those away\u2014save them for your fabric storage. Third, don\u2019t open fabric until you\u2019re ready to use it: the longer it\u2019s exposed to air, the more moisture it picks up. Fourth, if you\u2019re using fabric for high-stress parts (aerospace, automotive, medical), ask your supplier for moisture-tested fabric. I do regular moisture tests on my stock\u2014we test 5 random rolls every month to make sure absorption is under 0.3%, so my customers don\u2019t get stuck with damp fabric mid-project.<\/p>\n

Let me wrap this up with a quick example to make it real. Last quarter, a guy who builds custom carbon fiber bike frames came to me because he was having consistent delamination issues. He\u2019d been buying fabric from a big online retailer, storing it in his garage, and his tests showed his parts were only hitting 80% of the required strength. When we tested his leftover fabric, it had 0.6% moisture\u2014way above the standard. We switched him to our fabric with the hydrophobic sizing, and added a dehumidifier to his storage, and his delamination problems stopped. He told me he saved thousands in wasted materials and missed deadlines because he understood the moisture absorption issue. That\u2019s the stuff that makes me happy as a supplier\u2014not just selling fabric, but helping people not make avoidable mistakes.<\/p>\n

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If you\u2019re working on a project, whether it\u2019s a small hobby build or a large industrial part, and you have questions about carbon fabric moisture, sizing, storage, or need a reliable supply of tested, low-moisture carbon fabric, feel free to reach out to talk through your needs. I\u2019m here to help, not just make a sale.<\/p>\n

Sports Equipment<\/a> References<\/p>\n

    \n
  1. Averill, B. A., & Eldred, P. A. (2016). Materials Science and Engineering: Principles and Applications. Cengage Learning.<\/li>\n
  2. Johnson, R. T. (2020). Carbon Fiber Composites: Properties, Processing, and Performance. CRC Press.<\/li>\n
  3. Smith, L. K. (2018). \u201cMoisture Absorption in PAN-Based Carbon Fabrics for Aerospace Applications.\u201d Journal of Composite Materials, 52(12), 1645-1658.<\/li>\n<\/ol>\n
    \n

    Jiaxing Rongjin Intelligent Technology Co., Ltd.<\/a>
    As one of the most professional carbon fabric suppliers in China, we have world-leading production equipment and strong manufacturing capabilities. Please rest assured to buy high quality carbon fabric in stock here from our factory. Contact us for quotation.
    Address: No.503, Building 1, Xicundai Road 228, Honghe Town, Xiuzhou District, Jiaxing City, Zhejiang Province, China
    E-mail: vivi@rongjinsmart.com
    WebSite:     https:\/\/www.carbonfibers-china.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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