13th International Symposium on Advanced Science and Technology in Experimental Mechanics

Design of Laminated Flooring Materials
with Soft Underfloor Layer to Prevent Femur Fracture
UNIVERSITYOFYAMANASHI

Kaito SHINMURA, Yasumi ITO, Yoshiyuki KAGIYAMA, Ryuichi YAMADA,Tatsuya FUKUOKA and Tomotaka MATSUBARA
University of Yamanashi
E-mail：g18tm014@yamanashi.ac.jp, yasumii@yamanashi.ac.jp

Results & Discussion

Introduction

Comparison of the maximum transmission load on each flooring materials

Prevention of femur fractures in elderly people due to falls has become urgent task in the superaging society of Japan, since the fractures cause the long-term nursing care1).
Physical countermeasures can be considered for a fall fracture.

830%

Maximum transmission loadFmax [kN]

Stroke18%

Therefore, various life support devices for preventing fall
fractures have been developed in the super-aging societyof Japan.

Dementia

Infirmity due to aging
16%
Bone fracture/fall

11%

13%

Arthritis

12%

OthersPercentage ofcauses the long-term nursing care2)

Safetyflooring material

Fall prevention
walkers

Hip protectors

Countermeasures against falling fractures of flooring materials

Fall65432S• 2500mm2 was the same area as the impact surface ofthe weight. Therefore, there was no influence ofbuffering properties by laminating.

Load cell(Floor bottom)

10000mm2 (100×100mm)<Comparison of U-1 and S + U-1>
• Only the impact area of the weight was compressed in
the underfloor material U-1.
• It could be confirmed that the hard surface layer S wasdeflected in S + U-1, and U-1 was compressed in anarea larger than the contact area with the hard surface
layer at the impact of the weight.

S + U-1

That is, the soft underfloor layer receives impact on asurface wider than the impact surface of the hard surface
layer,since the surface layer is hard.

S + U-1

S + U-2

Details of floor materials

Underfloor layer

Material
Resin base material
EVA foam
PVC resin

U-2+Thickness [mm]Hardness56
ASKER C 26
4.5

<Comparison of S + U-1 and S + U-2>

S + U-2

ASKER C 43

Glass fiber cloth• The area of the flooring material used 2500mm2 (50×50mm) and 10000mm2 (100×100mm).
• 2500mm2 was the same area as the impact surface of the weight.

Stress σ [MPa]Stress-strain compression curves of the soft underfloor layer
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0

Static compression test was conducted using force tester(MCT - 2150, A & D Company, Limited) .

U-1
U-2

Underfloor layer（20×20mm）

U-1 did not show a large increase in stress with
U-1 a constant gradient up to the strain of 0.8.
to a strain of 0.2

0.2

0.4
0.6
Strain ε [-]0.8

1U-1 was the soft underfloor layer
with lower rigidity than U-2•Weight

We measured the pressure acting on the lateral femoral trochanter.
As a result, the weight assuming elderly men was set to 1.022kg.

Drop impact tester<Dummy skin>Details of dummy skin

Name

Size [mm2]Hitohada
729(27×27mm)
gel

Thickness[mm]

Hardness

10

ASKER C 7Pictures

The soft underfloor layer receives impact on a surface wider than the impact surface of thehard surface layer when the area of the laminated flooring material is larger than the impact
area of the weight, since the surface layer is hard.
Laminated flooring material combining the hard surface layer and low rigidity softunderfloor layer reduced the fracture risk when the area of the flooring material was larger
than the impact area of the weight.
From the state of deflection of the surface layer, it was suggested that the impact area of thesoft underfloor layer will fluctuate due to the difference in rigidity of the surface layer.

Acknowledgments
High speed camera

Dummy skin was used hitohada gel (EXSEAL CO., LTD.).
In our previous research3), it had buffering properties comparatively
close to that of soft tissue which was muscle and fat.

••

Fall heightIts height was the average trochanter
0.865m height of male 20's assumed to fallfrom the standing position.

GreatertrochanterIn the laminated flooring material, U-1 was lower inrigidity than the U-2, so it was compressed on a widesurface to reduce the maximum transmission load. U-2 isless likely to be compressed by being subjected to impact
on a wide surface, and it is considered that the maximum
transmission load has increased.

Conclusions

Fall impact–simulation device and Experimental conditions• Impact tests that simulate falling were performed on flooring materials.
• Impact load is applied to the test piece by dropping a weight.
• The transmission load transmitted through the dummy skin and flooringmaterials was measured with the load cell.
<Weight><Fall height>• In S + U-2, the underlying underfloor material U-2
was hardly compressed.

Laminated flooring materials is no instability in walking, difficulty in advancing thewheelchair, etc. there are merits such as ease of use on a daily basis. From that, it can be said
that combining soft underfloor layer under general flooring materials is a useful tool for
reducing the fracture risk. From the state of deflection of the surface layer, it is predicted thatthe impact area of the soft underfloor layer will fluctuate due to the difference in rigidity of thesurface layer. Therefore, it is necessary to select soft underfloor layer suitable for various rigid
surface layer.

U-2 U-2 showed a steep linear increase in stress up
0

Before impact and at maximum impact

U-1
Laminated flooring materials

SymbolS
U-1

S+U-2

Weight(Femur)

Flooring material

U-2S+U-1

Before impact and at maximum impact

Dummy skin（Muscle fiber・Fat）

Underfloor layer

U-1

U-2

• The load was greatly reduced
by using U-1, U-2.
• As the flooring material area
increased, the maximum
transmission load reduced at
the laminated flooring material
S + U-1 and increased most in
the laminated flooring material
S + U-2.
• Only the laminated flooringmaterial S + U-1 (2386 ±79N) of 10000mm2 wasreduced below the fracture load（the average fracture load of3440 N of the elderly）.

S + U-1Flooring conditions

SU-1

2500mm2 (50×50mm)

Materials & Methods
Surface layer

25002mm
10000

70

Simulate falling

The purpose of this study
Impact tests that simulate falling were performedon flooring materials. We consider falling fracture
countermeasures in consideration of everyday
ease of use flooring materials.

mm21

It have been devised such as surface processing for slip prevention and softening of the surface
have also been performed. However, there have been problems such as instability at the feetand difficulty in wheelchair progression, and no great effect has been obtained. Therefore, it isnecessary to consider falling fracture countermeasures in consideration of everyday ease of use
flooring materials.

VarietySurface layer

Oct. 30-Nov. 2, 2018,
Kaohsiung City,
Taiwan (ROC)

Weight(Femur)
Dummy skin（Muscle fiber・Fat）
Surface layer
Underfloor layer
Load cell(Floor bottom)

This work was supported by JSPS KAKENHI Grant Number JP16H03134. The authors would like to thank
EXSEAL CO., LTD., for providing hitohada gel which is sample material. The authors would like to thank Mr.
Ikeda of TOPPAN PRINTING CO., LTD. for advice on this research.

References
1) Ota, T., Harada, A. and Tokuda, H.: Cost-effectiveness of hip fracture in Japan (in Japanese), Japanese journal of geriatrics, 39(2002), 483-488.
2) Ministry of Health, Labor and Welfare, Summary Report of Comprehensive Survey of Living Conditions (2013).
3) Fukuoka, T., Ito, Y., Kagiyama, Y., Watanabe, M., Takahashi, J., Daimaru S. and Nemoto, T.: Experimental study on buffer
characteristics of soft tissue, Proceedings of 48th Symposium on Stress-strain Measurement and Strength Evaluation, (2017), 7-12.