a b s t r a c tThe natural frequencies of the flapwise bending vibrations of a nonuniform rotating nanocantilever has been calculated, considering the true spatial variation of the axial force due to the rotation. The area of the nanobeam cross section is assumed to change linearly. The problem has been formulated using the nonlocal Eringen elasticity theory and it was solved by a pseudo spectral collocation method based on Chebyshev polynomials. The effect of the nonlocal small scale, angular speed, nonuniformity of the sec tion and hub radius on the vibration behavior of the nanocantilever is discussed.

The paper presents a nonlocal cracked-rod model from which we have analyzed the torsional vibrations of a carbon nanotube with a circumferential crack. Several types of boundary conditions, including the consideration of a buckyball at the end of the nanotube, have been studied. The nonlocal Eringen elasticity theory is used to formulate the problem. The cracked-rod is modeled dividing the cracked element into two segments connected by a torsional linear spring whose stiffness is related with the crack severity. The effect of the nonlocal small-scale parameter, crack severity, cracked section position, different boundary conditions and attached mass are examined in this work.

This paper presents and analyses the behaviour of aramid composite plates subjected to low and medium impact energies. In order to study the material behaviour under impact loading, experimental tests have been performed using a drop-weight tower and a pneumatic gas gun within the range of impact energies (20 J E imp <<600 J). The plates are impacted by hemispherical impactor and spherical projectile for drop-weight and impact tests, respectively. The influence of areal density is also evaluated in terms of absorption energy. Energy Profile Diagrams (EPD) are used to identify the penetration and perforation thresholds enabling the definition of the nopenetration, penetration and perforation zones. The results revealed that there is a greater energy absorption capacity in thin plate than in thick plate for low impact energy values. However, areal density is relevant in the energy absorption capacity for high impact energy values.

In this work, seven different types of fabrics based on para-aramid yarns with different interlacing geometries and reinforcement polymer matrix have been characterised and compared from yarn level to weave level. Mechanical properties such as maximum stress, failure strain, and elastic modulus have been obtained from uniaxial tensile tests, while the inter-yarn friction coefficients (s tatic an d ki netic) ha ve be en ob tained by a combination of single yarn pull-out tests and an analytical model. Results show that mechanical properties are quite similar at yarn level but different at fabric level. Thus, the geometry, orientation and section of the yarn play an important role in the mechanical properties of the fabric. As an application of these results, a mesoscopic three-dimensional numerical model has been developed, and simulations of ballistic impact test have been carried out validating the model with experimental tests.

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