Altair Engineering : Mastering the Slapshot with Speed, Power, and Simulation

In hockey, the slapshot is the fastest, most powerful shot a player can perform. During the 2012 NHL All-Star Skills Competition, Boston Bruins captain Zdeno Chara unleashed a blistering 108.8 mph slapshot, which gave him the record for the world's fastest slapshot that still stands today. We think it's safe to say that Chara's 6'9", nearly 260-pound frame helps him generate some staggering power.

The slapshot earned its name because, you guessed it, players "slap" the ice slightly behind the hockey puck. From there, they use their weight to flex the hockey stick, transferring energy from themselves, to the ice, then lastly to the puck.

This may seem counterintuitive but hitting the ice before striking the puck creates a slingshot-like effect where the flexed stick's potential energy transfers from the player to the ice. This is what makes the puck fly through the air faster than it would have if the player had struck it directly.

While speed, location of contact, and timing all contribute to this mighty shot, so does the composition of the hockey stick itself. When hockey was just a fledgling game around the mid-1800's, hockey sticks were composed of a single piece of wood. But as players realized these sticks were brittle and prone to break, designers started manufacturing them with multiple layers of wood, which made the sticks hardier and more flexible.
Why Is It So Important to Have a Flexible Stick?

Since the 2000's, drastic improvements in player strength, training, and sports equipment have brought a new level of intensity to the sport. By studying the data on the NHL's hardest shots, it's easy to notice that around the year 2000, the league's shots started getting way faster. It's no coincidence that this was also the time players started using sticks made from composite materials. Composite sticks offer the flexibility and strength of wood but weigh less, which helps players handle them better and swing them faster, thus generating more force.

To compare the performance of both materials, we simulated this "slingshot" phenomenon with Altair® Radioss®. Using sticks made of both wood and composites, we wanted to find out how much of a difference the introduction of lightweight composite materials in sports equipment, specifically hockey sticks, has made in player and game performance.

Modeling the Sticks parts we were testing, Radioss was the ideal tool to carry out the slapshot simulations and observe structural behavior. For pre- and post-processing, we used Altair® HyperWorks®.

To model the hockey sticks, we first had to define each stick's material information. To accurately represent the composite model, we wrapped a carbon fiber-reinforced polymer layer material around the stick's shaft and blade sections. The shaft itself was hollow, while the blade was filled with foam material.

For the composite layers, we defined the material with Altair® Multiscale Designer®, an application which allows for the input of constituent fiber and polymer matrix material properties, along with a fiber volume fraction to calculate validated homogenized material properties for the composite material. Simulation-driven design tools like Multiscale Designer and Altair® OptiStruct® are powerful implicit solvers for composite materials.

In addition to homogenization, Multiscale Designer also allows for dehomogenization, which helps users assess stress and strain at the fiber and polymer matrix micro-level, enabling full progressive damage and plasticity material behavior.
Composite modelingWood modeling

Next, we had to define both sticks' proper rotation during the swing and contact with the ice. The wind-up for a slapshot isn't just a simple rotation of the stick around one specific location. When taking a swing, players position the shaft and face of the blade toward the puck at an inclined orientation.
Stick orientation during a typical slapshot swing

To mimic the player's hand positioning, we used a 4-bar mechanism approach was used, as seen below. The two moving joints represent the player's hands, linked by the shaft. With that, we defined a reasonable kinematics representation of the hands on the stick.
Taking the Slapshots

Setting the initial rotation velocity for the sticks at 550 rad/s, our virtual players took their shots. After simulating the slapshots, the results of the wood vs. composite stick were unsurprising. While each stick had different interactions with the floor, the stiffness of the shaft was what controlled the contact effort.

The composite stick had a much higher amount of control over the puck and thus generated more shot power than its wooden counterpart. Using the simulations to exhibit the slingshot effect, we can see that the stored energy does indeed transfer through to the puck as soon as the stick hits the ground.

Although each stick approached the puck at the same speed, the wood blade's velocity was slower than the composite blade just before impact on the puck because of the wood blade's poor puck control. The composite stick's slapshot clocked in at 66.4 mph, while the wood stick's shot clocked in at 54.9 mph. While we didn't exactly break any NHL records, we confirmed that the science of a slapshot relies on power, precision, and high-tech hockey stick design.
Conclusion

There's no doubt that multiphysics design tools will play a vital role in advanced sports equipment development. With access to advanced material behavior insights, engineering and design teams can perform more reliable, more accurate simulations with fewer iterations and lower costs. Gaining a competitive edge in the sports industry - much like in the sports themselves - begins with utilizing the right tool at the right time.

Altair® Radioss® is a leading analysis solution to evaluate and optimize product performance for highly nonlinear problems under dynamic loadings. Used worldwide across all industry sectors, it improves the crashworthiness, safety, and manufacturability of complex designs. For more information on solutions for complex multiphysics scenarios, visit www.altair.com/radioss/.