{'fraction_non_alphanumeric': 0.020134228187919462, 'fraction_numerical': 0.0, 'mean_word_length': 5.330188679245283, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Damping modelization of auxetic foams

Auxetic (negative Poisson's ratio) cellular materials expand in all direction when pulled in only one, thus behaving in an unusual manner compared to 'classical' materials. Negative Poisson's ratio honeycombs and open cell foams have shown increased shear modulus, indentation resistance and low cut- off frequency acoustic properties. In this paper FEM microstructure models are used to compute the static and viscoelastic properties of closed-cell and two-phase foam composites. The complex modulus of the materials is calculated making use of the correspondence principal and evaluating the strain energy distributions for the different phases. The results are compared to the ones given by models representing a global in-plane uniaxial loading. The static and storage modulus values of two-phase composite foam are significantly enhanced by the presence of a re-entrant (auxetic) skeleton layout. The loss factor shows also a significant sensitivity on the volume fraction and strain energy distribution on the microstructure unit cells. Static and free-vibration simulations on sandwich beams with different core cellular materials show that it is possible to obtain both enhanced stiffness per unit weight values and modal loss factors using two-phase cellular solids with a re-entrant skeleton.