JEC COMPOSITES MAGAZINE - Special Issue Composites for Sports, Health & Leisure - November 2020 - 52

APPLICATION sprinting shoes

Future of sprinting:
spikeless CFRTP sprinting shoe
A breakthrough shaping technology using preformed
randomly-oriented ultra-thin CFRTP tapes now makes
it possible to achieve the finest detail moulding with
CFRTP, as accomplished in the spikeless sprinting
shoe developed by Asics Corporation.

sics Corporation opted for this
type of composite material
for this project as random-fibre composites have the potential to
achieve fine-detailed mouldability
for shoe sole structures. However,
manufacturing high-quality thinwalled shoe soles using the current
random-fibre composites is quite
difficult.
Innovative technologies
The team developed five key innovative technologies: 1) precise spreading to fabricate ultra-thin tows; 2)
high-speed fabrication of high-quality ultra-thin unidirectional (UD)
tapes; 3) uniformly scattering of
chopped UD tapes; 4) unique preforming technology for all shoe sole
shapes; and 5) appropriate control of
fibre length and resin properties.
The precise spreading technology
makes carbon fibre tows thinner at
a thickness of 0.03mm. An in-situ
polymerizing thermoplastic epoxy
resin is employed as the matrix. As
the viscosity of thermoplastic epoxy
resin before polymerizing is very low,
resin impregnation into spread tows
is quite effective. Furthermore, resin
impregnation becomes more effective when the company's original impregnation technology is employed,

so that void-free ultra-thin UD tapes
can be fabricated at high speed. The
UD tapes are then uniformly scattered and laminated. The preform
for the sprinting shoe sole is automatically manufactured by a unique
preforming technology where the
thickness of a shoe sole can be specifically engineered for 20 separate areas
with a precision of 0.2g. Additionally,
material waste reduction was improved and the fibre length and resin
properties were adjusted for the manufacture of the sprinting shoe sole
structure.

Dr Norihiko Taniguchi,
Manager, Institute of Sports Science
Asics Corporation

A manufacturing
process of spikeless
CFRTP sprinting shoe
sole and comparizon of
cross section after manufacturing between
typical sprint spike
and spikeless CFRTP
sprinting shoe.

with world-class athletes under various track surfaces and weather conditions. During the prototyping stage,
the composite manufacturer developed the CFRTP material based on
randomly-oriented ultra-thin tapes
for sprinting shoes. They adjusted the
tape length for excellent mouldability
and durability through basic research
with the university. The matrix resin
manufacturer redesigned the matrix's
glass transition temperature to prevent the sprinting shoes from melting
due to the frictional heat between the
shoes and the ground.

Successful partnership
The innovation was developed
through an industry-academia collaboration. Product, composite material,
and matrix resin manufacturers as
well as the university were challenged
to create an out-of-the-box sprinting
shoe. At first, Asics Corporation proposed a unique concept using carbon fibre-reinforced thermoplastics
(CFRTP) mainly based on conversations with various athletes and scientists. Then, they designed the sprinting
shoe sole utilizing parametric design
and finite element analysis. The shoe's
performance in terms of the athletes'
biomechanical values and mechanical
properties was evaluated after prototyping. Wear trials were conducted

jec composites magazine / November 2020 / SPECIAL ISSUE Sports, Health & Leisure

JEC COMPOSITES MAGAZINE - Special Issue Composites for Sports, Health & Leisure - November 2020

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