Freezing temperatures and harsh Arctic conditions didn’t deter two extreme athletes from a 348-mile trek from the south to the northernmost point of the Norwegian island of Spitsbergen. Eric Folz, an engineer at Ticona, the engineering polymers business of the Celanese Corporation, and Mike Fuchs, a full-time photographer, embarked on a three-week tour dubbed “Mission Icefox.” In this frigid climate, a man is only as good as his equipment and these men each relied on one important item during their journey – a composite sled.
Folz and Fuchs skied across the Arctic pulling pulka sleds loaded with necessities: Pulkas are shell-shaped sleds, resembling the front half of a canoe, with flat runners. Hikers often use them to transport equipment over snow-covered terrain. “The pulka represents a less strenuous means of transport for the two athletes and for their equipment essential for survival over the long ski tour,” says Henning Kull, head of communications for Ticona Europe.
“The reliability of the sled was of vital significance to us,” says Folz. “We couldn’t take the equipment essential for survival like satellite phone, gas cooker, gas, tent, clothing, etc., more than 348 miles in 23 days without it.”
The sleds were made from Celstran continuous fiber reinforced thermoplastic (CFR-TP) composites and ultra-high molecular weight polyethylene GUR®, a special polyethylene that is shatterproof and scratch resistant even under extreme stress.
Each pulka measures 67 x 25 inches and weighs only 5.2 kilograms (11.5 pounds) but has a maximum load of 80 kilograms (176.3 pounds). “All the pulka components were designed for optimum support for the expedition participants,” says Kull. The runners are made from GUR and the shell from CFR-TP unidirectional (UD) tapes, which provide excellent stiffness, help prevent deformation and maintain load-bearing capacity no matter what the terrain.
Acapulka – a Norwegian company that creates expedition equipment for journeys to the Arctic, Antarctic and Greenland — designed and manufactured the sleds. Ticona supplied the Celstran CFR-TP UD tapes.
The CFR-TP offered many benefits. Dr. Simon Scholl, engineer at Acapulka, says that carbon fiber’s measure of stiffness is three times higher than aluminum. “Another advantage of composites, in this case, is that they are especially suited for thin-walled structures like the pulka sled and give more design freedom,” he says.
Teams from both Ticona and Acapulka discussed the heavy loads the pulkas would be exposed to during the Arctic trek. “We improved the glide characteristics with a lower friction outer skin, reducing the weight by using materials designed to do just that, and increasing wear resistance with a carbon fiber outer skin,” says Alexander Bierwald, director of Acapulka. The fiber/polyethylene matrix combination selected also is very light weight and ensures low moisture absorption.
Acapulka used an isotropic laminate structure to layer the sled with the unidirectional tapes. After the tape placement, the part is set under vacuum and heated up above the melt temperature of the polyethylene matrix, then removed from the mold after cooling. The consolidation process only takes about 30 minutes.
Both pulka sleds underwent testing before embarking on this intense journey. The most important structural tests on the sled shell included a drop test to simulate the maximum conceivable impact during an expedition. The shell also was tested for fatigue, tip and track stability at high speeds as well as in deep snow. Another concern was the friction properties of the runners. “All the tests were performed at cold to very cold temperatures, -15 to -35 degrees Celsius,” says Kull.
Both pulkas passed all the tests. “We were so impressed with the results of each test, and the sleds appeared as if they could be used again after this voyage,” says Kull. “The expedition would not be at any risk from material failure, as these materials were delivering ultra-high performance.”