Storage modulus foam

What is storage and loss modulus in viscoelastic materials?

The storage and loss modulus in viscoelastic materials measure the stored energy, representing the elastic portion, and the energy dissipated as heat, representing the viscous portion. The tensile storage and loss moduli are defined as follows: Similarly we also define shear storage and shear loss moduli, and .

Does polyurethane foam have dynamic mechanical properties under different strain rates?

Polyurethane foam (PUF) is widely utilized in cushioning and energy absorption applications, owing to its cellular structure, that provides high damage tolerance under compression. This study explores the dynamic mechanical properties of PUF with varying densities under different strain rates.

Are polymeric foams viscoelastic?

This work explores the viscoelastic behavior of two types of polymeric foams: an open-cell melamine foam and a closed-cell polyurethane foam. Experimental measurements were carried out on a torsional rheometer to estimate the complex shear modulus as a function of both temperature and frequency.

How do you calculate the modulus of closed cell foam?

Thus, the modulus of the closed cell foam can be calculated from a simple additivity assumption as equal to the sum of moduli from the cell edges, cell faces, and internal gas pressure (Eq. 4.23) . Where q> is the fraction of solid in the bubble edges and 1- q> is the fraction in the cell faces.

What are the mechanical properties of foam?

As a consequence, the mechanical properties of foams are time/frequency-dependent and viscoelastic phenomena such as relaxation, creep, hysteresis and load rate dependence can be observed. Temperature is another important factor that may also influence significantly their response (Ferry, 1980; Lakes, 2009).

What is the contribution of gas trapped in closed cells to foam modulus?

The pressure resisting compression and contributing to the foam stiffness is the difference between the calculated p and the internal gas pressure under no strain (p '). Thus the contribution of the gas trapped within closed cells to the foam modulus is given by Equation 4.22.