Abstract
The floor of rolling-stocks will be in the most severe condition when it has to support concentrated compressive load such as the weight of a woman carrying heavy luggage and standing on a high heel. Particularely is it the case with the floor of rigid plastic foam sandwich, the most delicate material with acoustic and thermal insulation effect, but not tough enough against the concentrated compressive load.
The formulas given below give the relations between the rigidity of the face plate, the compressive modulus of elasticity of the core and deflection of the face, when the rigid plastic foam sandwich floor supports such concentrated load.
w=P/8πD(a2-b2/2+b2logeb/a) (A)
Ec=64Dtc/(a2-b2)2 (B)
in which
D=EFtF3/12(1-μ2)
w: deflection of the face
P: concentrated compressive load
a: radius of loaded circular area of the core
b: radius of bottom surface of a high heel
Ec: compressive modulus of elasticity of the core
tc: thickness of the core
EF: flexural modulus of elasticity of the face
tF: thickness of the face
μ: Poisson's ratio of the face
D: flexural rigidity
from (B), we find
a2=b2+8√D·tc/Ec (C)
From fomulas (A) and (C), we obtain the maximum deflection of sandwich or the deflection of the face w. But w/tc must be less than the proportional limit strain of the core. The calculated value of deflection w was found to be 1∼1.5 times as high as the experimental value.
