Carbon fiber is an incredible material with unique qualities that make it ideal for some product applications. It’s exceptionally strong and lightweight, is highly wear resistant and extremely durable. Its radiolucent properties make it a great fit for radiology products and its thermal conductivity is critical to many applications.
Shop for carbon fiber online and you’ll find carbon fiber sheets in a wide range of materials and price points. In this article, we’ll help you break the code and understand what factors are driving the cost when you’re buying carbon fiber.
Basic Material Costs
Carbon fiber sheets and parts are made up of two materials – carbon fiber (fabric or tows) and resin (often epoxy).
Factors that influence price include:
1) sheet thickness
2) fabric weight (3k, 6k, 12k)
3) fabric layup and
4) manufacturing method.
Let’s break them down and how each one affects cost.
1. Sheet Thickness
Aside from sheet size, sheet thickness is a key factor in determining price. The thickness of the sheet is based on the number layers of fabric in the sheet. For example, a ¼” sheet is 16 layers of 6k fabric infused with resin. The more layers of fabric required to build thickness, the higher the cost.
Also, it’s important to note that if you’re replacing an 1/8” sheet of wood, aluminum or steel with carbon fiber, you won’t need an 1/8” thick piece of carbon fiber. Talk to your supplier for advice to determine what thickness makes most sense.
2. Fabric and Fabric Weight
Fabric weight has a significant affect on price:
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6k fabric is considered a mid-range fabric thickness and very common in the industry. It’s practical and easy to work with and cost effective for many applications.
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A 3k fabric is a smaller, finer, lighter weight weave. It’s especially useful for molds with tight corners and applications that require a lighter weight fabric. However, because it’s lighter, it will require more layers of fabric to achieve the same panel thickness as a 6k, making it more expensive to produce. It will also yield a stronger, more rigid product.
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12k fabric is also an option, though a little less common. It can be a more cost effective option compared to 3k or 6k fabric. A 12k weave has larger tows (think burlap vs. cotton), so it takes fewer layers of fabric to create a thick panel. If you don’t mind the larger weave, buying carbon fiber sheets made of 12k may help you save money. Some customers find it more challenging to get a clean edge when cutting it, though it’s totally possible with the right tools and machine speeds.
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Use of specialty fabrics like unidirectional weaves, harness weaves or specialty patterns will also have a significant influence on the price.
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True “aerospace grade” fabric can be significantly more expensive than industrial quality carbon fiber and offers no noticeable additional benefit for most customers. However, some companies use the term “aerospace grade” purely for marketing purposes. If you require certified aerospace grade material, you can expect to pay a premium for it.
3. Fabric Layup
Fabric layup will also influence the cost of a carbon fiber sheet. A standard layup is a 0/90, where each layer of fabric is laid on top of the next at a 90-degree angle. Customers with specific strength requirements may require a quasi-isotropic layup or a special combination of layered materials to provide the material qualities they need. Layering in fiberglass, kevlar, basalt and other products can be another way to trim costs depending on your strength and performance needs.
4. Manufacturing Method
A wet layup is the least expensive way to make a carbon fiber sheet and is a common method used by DIY makers because of its relative simplicity. On the downside, this process can be imperfect and messy and result in inconsistent product and/or sheets with pinholes.
Vacuum infusion is a more complex process, creating carbon fiber sheets that are much more consistent in quality and less prone to air pockets or pinholes. In this case, dry fabric is laid on infusion tables, placed under a vacuum bag and infused with resin.
A hot press is also a common way to manufacture carbon fiber sheets. This process uses prepreg carbon fiber fabric which is coated in resin during the manufacturing process. The sheets are loaded into a press under heat and very high pressure. In many cases, hot press carbon fiber sheets are less expensive than those made through vacuum infusion. However, there are size and shape limitations with this method.
Resins also deserve a quick note as they also play a role in the cost of a carbon fiber sheet. Vinyl ester and polyester resins are generally the least expensive. They’re easy to use and have good mechanical properties. Epoxy resins are industry standard with excellent mechanical properties and provide higher strength and temperature resistance, though at a slightly higher price. High temp resins and other specialty resins are premium products that command higher prices.
Pinholes and Porosity – How Much Do They Matter?
It really depends on your application. Cosmetically, these voids will show up as tiny pinholes or air pockets. Materially, porosity compromises the structural integrity and long-term durability of the carbon fiber. However, if uncompromising strength isn’t absolutely critical and perfect appearance doesn’t matter, a carbon fiber sheet with pinholes may be totally fine for your needs. In many cases, an automotive clear coat can be applied to the surface to fill in voids for cosmetic purposes.
If this sounds like you, you may want to check out our Scrap Packs in ½ lb. or 1 lb. sizes where we sell slightly imperfect carbon fiber. If you have a specific size or thickness in mind, give us a call and we’ll see what we have available.
How Do You Decide What’s Right For You?
Everything depends on your application. When we’re working with customers, here are the questions we ask:
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How strong does it need to be? Will a standard 0/90 layup meet your needs or is it worth spending more money on specialty materials or layup to insure the material is strong enough to handle to the load?
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How important are cosmetics? Do pinholes matter? If you’re looking for perfection, find a company that uses vacuum infusion manufacturing process. (I happen to know one called Protech Composites.) If pinholes or cosmetics don’t matter, a hot press sheet may be cheaper and fine for your needs.
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You can also save money by a carbon fiber sheet made of 12k. The trade-off? The weave will be larger and material may be just a little more challenging to cut. This one is purely a personal preference. Some dislike 12k, some never notice the difference.
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Finally, if you see a carbon fiber sheet for a price that’s so low you can’t believe, it’s probably not 100% carbon fiber. Sometimes off-shore manufacturers will place cheap black plastic filler between layers of carbon fiber. If it meets your need, you don’t need 100% carbon fiber and the price is right, maybe you buy it anyway. Just consider yourself warned that it might not be what’s advertised!
Final Tips for Cost Optimization
No doubt, carbon fiber is an expensive material but there are ways to manage your costs. Your supplier is your best resource to help you determine whether carbon fiber is a good fit and how to optimize your spend and determine the most cost-efficient way to meet the needs of your application. A good supplier will talk you through your cost alternatives and explain the pros and cons of each. In some cases, they can recommend alternative fabrics or layups that can save you money. Also, ask for a quote with volume breaks to understand your options there as well.
We hope this was helpful. If you’re thinking about using carbon fiber, get in touch and we can talk about the possibilities. We’ll be happy to walk you through the process and provide a quote with your options.