Shaft University – Materials 101

How much do you really know about golf shafts? How much do you want to know?

You’d be hard-pressed to find a segment of the golf equipment industry where there is more confusion and misinformation among consumers. It’s time we start to clear things up.

As we begin our first session of Shaft University, it’s tempting to jump right into the fun stuff. But before we can tackle topics like flex, torque, bend profiles, and the real-world implication each has for how a shaft performs on the golf course, we need to begin with something a bit more basic. First, we need to understand what a shaft is before it becomes a shaft. We need to start at the foundation, and the foundation of every graphite shaft is the material.

With that in mind, by the end of this section, you should be able to answer the following questions:

• What are composite materials, and what role do they play in shaft construction?
• How are the material properties of shafts measured?
• Where and how do shaft companies source materials?
• What are the key benefits of composite graphite shafts?

MATERIALS OVERVIEW

We don’t expect you to memorize this stuff, but we wanted to provide a quick overview of some of the key terms that will be discussed in this section.

CFRP (Carbon Fiber, Reinforced Plastic) – The specific type of composite material used to produce shafts. CRFP is characterized by high strength to weight ratios.
FRP (Fiber Reinforced Polymer) – Composite material containing a matrix (resin) and reinforcement (carbon fiber).
Composite materials – A combination of materials which are more effective when used in combination
Graphite – Pure carbon with atoms arranged in a hexagonal-ring pattern
Polymer – A connected chain of carbon atoms
Resin/Epoxy – The bonding agent (glue) which holds carbon fibers together
Carbon Fiber – A polymer once it has been stretched and oxidized
Pre-preg – Carbon fiber which has been (previously) impregnated with resin (glue) to form a composite material.

While graphite shaft is the commonly-used description, every so-called graphite shaft is actually made from a composite – meaning, it’s comprised of two or more materials that are more effective together than when used by themselves. In this case, we’re talking about a mix of carbon fiber and resin/epoxy. The technical term for the finished product is carbon fiber, reinforced plastic (CFRP). Graphite shaft manufactures believe that CFRP is superior to steel in every meaningful way.  I.e., it’s lighter, stiffer, stronger, and offers greater versatility to achieve specific design goals. We should mention that across the industry, some use the term CFRP, while others use FRP. Understand that they’re one and the same and can be used interchangeably.

Back to high school chemistry for a minute; Graphite is pure carbon with atoms that are arranged in a particular hexagonal-ring pattern. A polymer is a connected chain of carbon atoms. Carbon fibers are what the polymer becomes once it is stretched and oxidized. You can think of polymers as a bunch of graphite atoms standing next to each other. Carbon fibers are what those polymers become after a couple of minutes of Pilates and some time in an oxygen chamber.

The next step in building the foundation material is to combine the carbon fiber with a special glue (called resin or epoxy) to create the composite material. The resin/epoxy protects the fibers, and in turn, the fibers provide stiffness and strength that reinforce the resin. It’s textbook symbiosis.

At their most basic level, shafts are made from two elements – carbon fiber and resin.

In that respect, graphite shafts are a lot like a concrete patio in that there are two basic materials which make up the physical structure. In our patio example, rebar is positioned to keep the concrete from crumbling, just as carbon fibers need resin to keep from breaking. This is especially true for players with high swing speeds or a violent transition from backswing to downswing.

The composite materials shaft manufactures receive from suppliers arrive as rolls of pre-preg, meaning the carbon fiber has been previously impregnated with resin to form a single composite.

There are different ratios of carbon fiber to resin content which serve various purposes in shaft design. Carbon fibers are light and strong, whereas resin is heavier and can impact the stiffness of shaft.

In general, low resin content pre-preg is preferable (how’s that for alliteration?), because it allows manufacturers to create shafts which are both stiffer and lighter. It’s more difficult than designing shafts which are both heavy and stiff, which by comparison, is as easy as finding a Starbucks in Manhattan. Most every shaft manufacturer has an acronym; Fujikura uses MCFC (Maximum Carbon Fiber Content), Mitsubishi describes theirs as L.R.C. (Low Resin Content). The point everyone is trying to convey is that it uses pre-preg with some reduced amount of glue/resin.

In addition to the high strength-to-weight ratio, low resin technologies like MCFC tend to feel smoother because the carbon fibers (not resin) are doing more of the work during the swing. Understand that this has absolutely no bearing on performance, just as an 80 proof 15-year old single malt won’t get you any more drunk than a 3-year old version. The only discernable difference is that the latter tastes like lighter fluid.

That being said, there’s a floor to the quantity of resin required to maintain some structural integrity. Shaft manufacturers are inclined to push boundaries to see how far the carbon fiber-to-resin ratio can be taken, but there can be a fine line between maximizing performance and taking it a step too far. That final step can give you a better view of the Grand Canyon, but it can also, well, you get the idea.

There are also instances where companies like Fujikura strategically implement materials with higher resin content. With its HDCC Technology (High-Density Composite Core), a heavier, moderately stiff carbon fiber is paired with higher resin content composite to shove weight towards the tip section of the shaft. The primary benefit in doing so is to give club builders graphite shaft options (e.g., Fujikura PRO and Vista PRO) which can match the traditional swing weights of steel shafts.

PAN vs. PITCH Fibers

Again, let’s start with a couple of key terms that will serve as the foundation for this section.

PAN – Carbon fibers consisting of synthetic polymer resins
Pitch – Carbon fibers made from carbon-based materials (plants, crude oil, coal).

Hufflepuff and Gryffindor are to Harry Potter what PAN and Pitch are to carbon fiber composites.

In the first house, we have PAN (Polyacrylonitrile) Carbon Fibers, which use synthetic organic polymer resin and are typically classified as standard, intermediate, or high modulus (we will review modulus in the next section).

Residing next door are Pitch Carbon Fibers which are derived from earthy carbon-based materials like plants, crude oil, and coal. Pitch fibers are classified as intermediate, high, or ultra-high tensile modulus.

Pitch carbon fibers can be significantly stiffer than PAN fibers – about two times stiffer than the stiffest PAN carbon fiber available.

In terms of cost, Pitch materials are quite a bit more expensive for two reasons.

• Pitch fibers require a more intricate production process
• Pitch fibers are scarcer. As we know from basic market economics, when demand exceeds supply, prices go up.

There are several shafts on the market which use both Pitch and PAN carbon fibers. Fujikura’s Ventus is an example of a product that leverages both Pitch and PAN fibers. By adding Pitch 70 Ton carbon fiber full-length in the bias layer (the portion of the shaft where composite material is oriented at 45°), Fujikura is able to create a shaft with higher resistance to twisting, improving accuracy and tightening dispersion.

A final note and a topic we’ll perhaps dig deeper into later is the orientation (direction) of the materials. Where and how the sheets of material are placed is just as important as the material itself.

The three primary orientations are:

• 0 degree – along the length of the shaft (affects bending). Picture a hinge.
• 90 degree – perpendicular to the length of the shaft (provides hoop strength to prevent buckling and ovalization of the cross-section). This is where materials like Triax come in handy.
• +/- 45 degree (referred to as Bias) – These materials lie across the 0-degree materials at +/- 45-degree angles (affects twisting)

That’s a decent amount of information to digest, so without scanning back through the text, could you explain the differences between PAN and Pitch or list the two primary components of Fiber Reinforced Polymers?

Unidirectional vs. Woven

TOWS – Bundles of carbon fiber which range from 1,000-15,000 fibers

Unidirectional (One Direction was already taken) carbon fibers run in a single, parallel direction. The fibers lay flat in that direction and do not contain any gaps. Composites made of unidirectional carbon fiber provide maximum strength in the direction of the fiber. This tightly bunched pack of uncooked spaghetti you’re picturing is as accurate and straightforward an analogy as you think it is.

Woven materials can come in a variety of weaves and orientations. A plain weave carbon fiber looks like double-cut greens where “tows” (bundles of carbon fiber that range from 1k to 15k or 1,000 to 15,000 fibers) are woven in an over-under pattern, providing multi-directional stability.

There are two main types of woven materials; Spread Tow and Standard Tow. Standard Tow utilizes a basket-like weave where the advantage is structural stability in several directions. The primary downside is standard tow weaves are heavier which works against the whole “lighter, yet stable” concept.

Spread Tow is unique in that the tows are first spread flat before weaving. This reduces the “crimp” (where the fibers meet perpendicularly) of the fiber. Spread tow fabrics have increased material stiffness and are significantly lighter than standard tow weaves, which make it a more viable material across a broad spectrum of shaft weights. For example, in 2010, Fujikura developed the Blur line of shafts that utilized Textreme’s Spread Tow carbon fabric to deliver a lightweight profile with ample stiffness in an effort to generate faster swing speeds.

MATERIAL MEASUREMENTS

Even if you weren’t entirely sure what it meant, you’ve definitely seen modulus numbers before. When you glossed over references to 40-ton, 50T, 110 MSI, 130 MSI, etc. what the shaft company is trying to tell you is it’s using high-modulus materials.

It’s also the type of content marketing departments love to leverage because it takes very little to claim the use of high-modulus materials because consumers generally don’t have the first clue of what the company is referencing, and without a clear picture, it’s tough to differentiate between companies which use legitimately high-quality materials and those which use just enough to justify the “high-modulus” claim. The other reality is because it seems to be preferable (higher is better than intermediate or lower, right?) once one shaft company started down that road, others followed creating the “High-Modulus” bandwagon we see today. It’s a bit like the organic food movement of the early 1990s.

Tensile Modulus

There are many different measurements of composite materials, but they are most commonly measured for stiffness and strength. Tensile Modulus or “Young’s Modulus” measures stiffness by examining the elongation of a material under stress, when the deformation is elastic. Picture two people pulling on opposite sides of a 24” x 36” towel. The more resistant the towel is to separation (and its ability to return to the original 24” x 36” template), the higher the tensile modulus.

In simple terms, Tensile Modulus is a measurement of a material’s ability to withstand changes in length when tension or compression is applied. Materials with higher tensile modulus provide greater stability and strength.

Tensile Strength

The second primary measurement is referred to as Tensile Strength. This is the maximum stress a material can withstand before it breaks under tension. This time, picture two teams in a game of tug-o-war. Tensile strength indicates how much stress the rope can stand while being stretched from opposite ends without breaking. Higher Tensile Strength materials can be used to provide strength against ovalization, maintaining the structure, uniformity, and consistency of the shaft during the golf swing.

MATERIAL SOURCING

Shaft manufacturers utilize a variety of composite material suppliers. Nippon Graphite (NGF), Oxeon, Toray, SK Chemical, Mitsubishi Chemical, and Toho are some of the most popular suppliers to the shaft industry.

These suppliers also provide materials to other industries. Aerospace is the one advertised most often (perhaps because it sounds like the most cutting-edge), but composites are also heavily used in the biomedical, bridges and tunnel, automotive, and electronic packaging fields. Fujikura has often been first to market with certain technologies because of its long-standing relationships with suppliers. Think of it as friends with composite benefits. (e.g., Triax, Spread Woven). For example, Triax was originally developed for use in Department of Defense satellites. Fujikura found it offered structural benefit in its Speeder series of shafts (launched in 1995), which is the same year Amazon sold its first book. Other shaft companies would soon follow Fujikura’s lead using Triax and similar constructions to keep shafts from losing shape during the swing. Amazon would go on to make Jeff Bezos the richest man in the world. You can argue which one had a more significant impact. We’re sticking with Triax.

BENEFITS OF COMPOSITES IN GOLF SHAFTS

ISOMETRIC – Of or having equal dimensions

Since its debut in the mid-twentieth century, carbon fiber/composite shaft use continue to spread throughout the bag. It wasn’t that long ago that professionals used steel shafts in their drivers and e-woods. Some may recall that three of Tiger’s first four Masters victors came with steel-shafted woods. While the use of graphite shafts in irons and wedges has been slow, to say the least, the day may come when composites are used in every club in the bag.

As a point of reference, Fujikura started with graphite composites in 1974 when graphite first began replacing steel shafts in drivers primarily because graphite was lighter and more versatile. Since then, there have been quantum leaps in materials, construction, and cost which have created massive opportunities for everyone involved in the graphite golf shaft industry as well as golfers who continue to lie about how far we hit the ball.

The argument for using composite material throughout the bag is that it allows for more tailored designs than steel. Simply, carbon fiber composites are more versatile and enable designers to fine-tune the twisting and bending of the shaft independently (and in different sections of the shaft) in a way that steel doesn’t. With steel, it’s a choice between chocolate ice cream or vanilla. Composite materials are Baskin-Robbins 31 Flavors, Dairy Queen, Cold Stone, Max and Mina’s and Sebastian Joe’s all under a single roof.

A steel shaft, for example, can only be made stiffer by increasing the weight. The same is true when it comes to adjusting the twisting and bending properties of the shaft. Steel is strong in all directions, but high strength isn’t always necessary or even beneficial over the full length of a shaft, just as not every room in your house requires a deadbolt.

Composite materials allow manufacturers like Fujikura to localize the strength in finite areas within a design, creating shafts that are strong in specific areas but are also lighter in weight.

Spinach doesn’t always taste good, but it’s packed with valuable nutrients. So too can be discussions where the primary purpose is to build capacity and a basic understanding of important vocabulary. We know you’re eager to dive into the applications of shafts and soon enough we’ll be debating the role of flex and bend profiles while explaining why lower torque doesn’t always equal a straighter ball flight.

In its completed version, a golf shaft is akin to a well-cooked meal. Hopefully, you now have a reasonable handle on the list of ingredients and preferred grocery stores. If it’s not committed to memory, at a minimum, you’ve likely bookmarked this article for future reference.

Who is doing the cooking, and how are they coming up with the recipes? That’s the topic of our next segment, Design 101. We’ll tackle topics such as the history of design, the process of shaft design, and the role of different materials and shaft geometries.

Pop Quiz

1. 1. At the most basic level, graphite shafts are made from __________ & ___________.
2. 2. True or False: Pitch fibers can be twice as stiff as the stiffest PAN fibers.
3. 3. True or False: Every shaft designated as “high-modulus” contains the same type and quality of materials.

How much of this information was new to you?

What do you wish we might have included but didn’t? As always, we appreciate your comments and feedback.