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This study aims to investigate the damping behavior of the fundamental mode of a foam-filled carbon fibre reinforced polymer composite (CFRP) tube when subjected to base excitations. In particular, expanded polystyrene (EPS) foam balls (with negligible mass) of different sizes are used as fillers in the tube and the enhancement in damping ratio of the fundamental mode w.r.t the empty condition is evaluated for different intensity of base excitation. Shake table tests are performed on cantilever CFRP composite square hollow tube subjected to base excitation with varying amplitudes. The tube is filled with foam balls (of two different sizes) for varying depths of filling (no filling, one-third, two-third, and full). Accelerometers are mounted at different positions along the tube length and at the table to record the accelerations data for evaluation of damping ratio. From the recorded responses, frequency, mode shape and damping ratio of the fundamental mode are evaluated using a well-known approach. The damping ratio is noted to be around 1.41x (times) higher for the completely foam ball (bigger size) filled case under r.m.s base acceleration of 0.3 g when compared with the values corresponding to the empty case. The results suggest that the bigger foam balls enhance the damping ratio significantly without altering the natural frequency owing to additional energy dissipation in friction and impact generated through the sliding and collision of the balls while the tube is in motion.

A systematic investigation is carried out on how different parameters influence stress and strain concentration factors (SCF and SNCF) in a composite plate with a hole under uniaxial tension. Flat and singly curved composite plates have been modelled in ANSYS 15.0. The governing parameter includes: (i) size, shape and eccentricity of hole, (ii) number of plies, (v) fiber orientation and (vi) plate curvature. It is observed that different parameters influence the SCF and SNCF with varying degrees. For example, SCF may be as high as 7.16 for a square shaped hole. Also, SCF and SNCF are found to be approximately same in most of the cases. Finally, simplified design formulas are developed for evaluation of SCF for a wide range of hole size, eccentricity and fiber orientation.

Metal inserts are widely used particularly in bolted connections for joining composite members. In this work, a theoretical basis is provided for analyzing the damping behavior of a cantilever composite square hollow member embedded with metal inserts along its length. Analytic stress solutions around the boundaries of the insert and the member are introduced while deriving the expression of modal damping ratio. Kelvin–Voigt and amplitude-dependent damping models are considered for the formulation. Experiments are performed on the perforated composite tube reinforced with brass, copper, and steel annular inserts subjected to transverse base motion of varying amplitudes. The acceleration responses recorded from the tests are analyzed to evaluate the damping ratio of the fundamental mode. It is observed that the damping ratio evaluated from the experiments matches well with the proposed value. Furthermore, it is found that the damping ratio increases when the holes are reinforced with the inserts. The reason for the increase in damping stems from (i) frictional effect at the boundaries of the insert and the tube and (ii) material damping of the inserts. For example, the damping amplification of the tube with five steel inserts is noted to be around 3.0 and 2.1 times with respect to the unperforated and perforated (with holes) cases, respectively. [ABSTRACT FROM AUTHOR]

Advanced composite polymer matrix and their different manufacturing processes tend to develop pores of varying size and play a major limiting role in residual stress, damage initiation, matrix cracking, strength, and durability. Direct imaging or simulations to understand the pore formation mechanism in the viscous polymer is difficult. Ultimately, the mechanical performance of the solidified matrix needs better prediction. This paper presents a stochastic micromechanical model, including the effect of pores' formation on the polymer matrix's elastic properties. Theoretical homogenization based micromechanical models for polymer composites is reviewed in the first part. Later, a micromechanical model is proposed considering the different stages of pore formation in a polymer matrix. Polymer samples are fabricated for determining the pore distribution parameters and used appropriately in the proposed model to estimate the elastic properties for a given distribution and volume fraction of the pores. A modified Mori‐Tanaka homogenization approach and a differential scheme of inclusion of pores are incorporated in the model. Results obtained from the proposed model are compared with the experimental measurements, and a significant correlation is found. [ABSTRACT FROM AUTHOR]

Motivation is essential to maintain achieved targets in the long-term management of chronic diseases like obesity. Moreover, the role of motivation becomes even more important when the physiological set point tries to act against the achieved targets. In this brief communication the authors propose a rubric that should assist health care professionals in enhancing the quality of their communication skills, improving the delivery of obesity management, and optimizing therapeutic outcomes by helping their patients with obesity to manage their motivation drive.