Athletics

Early History of Composites

POLE VAULT

Early History of Composites

• 1900: Initially wood, then (from 1900) bamboo, in 1940-1960 some attempts to use steel (or aluminium)
• 1962: American athlete George Davies broke the pole vault record with a GFRP pole (fig.1)
• 1960’s: From 1960’s: glass fibre composite hollow tubes are generally used (fig.2) because of
  • Much higher energy storage
  • Large flexibility (up to 170° bending) combined with high strength
  • Made using a complex wrapping process of different kinds of textile prepreg layers on metal core
  • Not fully straight, tapered for easier demoulding

Recent Development

Recent Developments

• Composite layup is further optimised for each of the 3 layers (from in to out) (fig1)
  • “Spiral layer”: fibre in hoop direction to prevent oval shape during bending
  • “full body wrap”: unbalanced textile with most fibres in 0° (and some +/-45°), wrapped around
  • “Sail piece” more fibres in central region (trapezium shaped textile) to control bending
• More recently adding carbon fibres, for performance optimization and weight reduction (normally 1.5 to 3 kg) (fig.3)

Also used in variable bend poles, with a stiffer bottom section, which gradually transitions into a more flexible upper section

Recent Development

RUNNING

Recent Developments

• Many shoes have now a “carbon fibre composite plate” in order to stiffen the shoe under the metatarsal joints
• Best marathon shoes : thick midsole made from a highly compliant and resilient foam material,  to increase energy storage , stiffness compensated by carbon composite inserted plate
  • 2014: Zoot carbon running shoe, Ultra TT 4.0 (fig.8)
  • 2017: Nike Vaporfly , multiple models since then, like Nike VaporFly 4% Flyknit (2023) (fig.9)

Long-distance running studies have shown that these shoes can improve run times up to 4.2%

Early History of Composites

DISC THROWING

Early History of Composites

• Composites help realizing high moment of inertia
  • Important to keep the disc rotating/spinning while flying
  • Outer rim is steel, bronze or brass, while the top and bottom sides are alu, wood or composite (fig.6)
  • Diameter is 22 cm for men, 18 cm for women, weight of disc < 2 kg resp. 1 kg

Recent Development

Recent Developments

• Only recently, carbon fibre composites have been entering discus throwing (fig.7)
  • Top athletes prefer the highest moment of inertia (80-92% of the weight in the rim), hence composite shell must be as light as possible

Early History of Composites

JAVELIN THROWING

Early History of Composites

• Initially wood (Finnish birch), later steel or aluminium
• Nemeth (former javelin throwing Olympic champion) produces “hybrid” javelins: aluminium core with carbon fibre composite skin
• Unknown when first composite javelin was introduced

Recent Development

Recent Developments

• since 1986, new rules: CoM (centre of mass) should move 4 cm forward , to guarantee that it’s always ahead of CoP
  (centre of aerodynamic pressure), hence pitching down the javelin
  • Side effect: javelin “flies” not so far, previous records cannot be obtained anymore
• Hybrid carbon/glass fibre composites are optimised towards optimum stiffness, highest vibration damping to prevent vibrations
  (leading to aerodynamic losses), but min. weight is 800gr (men) or 600 gr (women)

PARA-ATHLETICS

• Carbon fibre composites are heavily used in
  • Racing wheelchairs (fig.10 ) where lightweight is most important
  • Prostetics (fig.11): mainly in running blades looking for an optimum in flexibility, strength and energy storage
  • Orthothics: composites are easily adaptable to the individual needs of the athletes

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