Asked by zxcv

A helmet has an open cell polystyrene foam liner that is designed to absorb the kinetic energy from an impact. The foam has a relative density of 10% and the Young's modulus of the solid polystyrene that the foam is made from is 1.5GPa. How much energy per unit volume, in J/m3, can the foam absorb if it is loaded in uniaxial compression to a strain of 80%? Please assume that C1=1.0 and C2=0.05.

U (in J/m3):
Answered by Writeacher
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Answered by 007
I worked with this equation:
sigma=C_2*E_s*0.1^2 = 750000[Pa]
Then for the energy:
U=sigma*s_densification= 750000*0.8=600000[J/m^3]
But the answer is incorrect.
Also, I know that E=C_1*E_s*0.1^2 =15[MPa] But I don't know how can I use it.

Some help please
Answered by abc
600000
Answered by abc
answer is 600000
Answered by Anon
not sure, I found it was 500000 J/m³
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