The rheological behaviour and thermal ageing characteristics of PP/MWCNT/glass fibre multiscale composites

Multiscale hybrid composites were prepared using varying weight percentages (0 to 5) of multiwalled carbon nanotubes (MWCNTs) as nanofiller and a fixed weight percentage (20) of short glass fibres as micro filler (in polypropylene (PP) matrix. The shear and extensional viscosity of the composites was measured using a capillary rheometer. It was observed that even at higher shear rates the synergism of micro and nanofillers in the matrix significantly enhanced the melt viscosity. The complex nanotube network entanglement with micro fillers and PP chains imparted restrictions to the polymer chain movements. The prepared samples were subjected to thermal ageing at 100°C for 4 days in hot air oven. After ageing, multiscale composite with 3 wt% MWCNTs exhibited 28.57% enhancement in strain at break, whereas the tensile strength and modulus reduced by 6.8% and 8% respectively. The fracture toughness properties like strain energy release rate and critical stress intensity factor were not affected for multiscale composite at the optimum content of 3 wt% MWCNT, even after thermal ageing.

Seawater effects on interlaminar fracture toughness of glass fiber/epoxy laminates modified with multiwall carbon nanotubes

In this work, the effect of seawater ageing on mode I and mode II interlaminar fracture toughness ([Formula: see text] and [Formula: see text]) of prepreg-based woven glass fiber/epoxy laminates with and without multiwall carbon nanotubes (MWCNTs) has been investigated. The first part of the investigation reports the moisture absorption behavior of multiscale composite laminates exposed to seawater ageing for ∼3912 h at 70 °C. Then, the results of mode I and mode II fracture tests are presented and a comparison of [Formula: see text] and [Formula: see text] for each type of material group and condition is made. Experimental results showed the significant effect of seawater ageing on [Formula: see text] of multiscale composite laminates due to matrix plasticization and fiber bridging. The improvement in [Formula: see text] of the wet glass fiber/epoxy laminate was about 50% higher than that of the neat laminate (without MWCNTs) under dry condition. It was also found that the presence of MWCNTs into composite laminates promotes a moderate increase (8%) in their [Formula: see text] as a result of the additional toughening mechanisms induced by CNTs during the delamination process. Scanning electron microscopy analysis conducted on fracture surface of specimens reveals the transition from brittle (smooth surface) to ductile (rough surface) in the morphology of composite laminates due to the influence of seawater ageing on the polymeric matrix and fiber/matrix interface.

MULTISCALE COMPOSITE 3D FINITE ELEMENT FOR LUNG MECHANICS

The lungs are the pair of organs where very complex internal microstructure provides gas exchange as the vital process of living organisms. This exchange in humans occurs within only 300g of tissue but on the surface of millions of alveoli with the total surface area of around 130m2. The extremely complex microstructure consists of micron-size interconnected channels and alveoli, which significantly change the size during breathing and remain open. These conditions are maintained due to existence of two mechanical systems – one external and the other internal, which act in the opposite sense, so that the lung behaves as a tensegrity system. Many computational models, with various degrees of simplifications and sophistication have been introduced. However, this task remains a challenge. We here introduce a 3D multi-scale composite FE for mechanics of lung tissue (MSCL). The model can be further used in generating computational models for mechanics for the entire lung and coupling to airflow.

Enhanced flexural and tribological properties of basalt fiber-epoxy composite using nano-zirconia/graphene oxide hybrid system

In this work, the synergistic effect of graphene oxide and nanozirconia on the flexural and tribological properties of basalt fiber/epoxy composites was investigated. At the first step, the nanofillers were surface-modified to improve their compatibility with the epoxy matrix. Then, several laminates were fabricated by varying the filler loading. The results revealed that the multiscale composite filled with 0.1 wt.% graphene oxide + 1 wt.% nanozirconia exhibited the maximum flexural strength and wear resistance. Compared to the neat basalt fiber/epoxy composite, the wear rate and friction coefficient of the 0.1 wt.% graphene oxide + 1 wt.% nanozirconia-filled specimen were decreased by 67 and 62%, respectively, whereas the flexural strength was enhanced by 50%. Scanning electron microscopy analysis clearly showed an enhanced fiber-matrix interfacial bonding for the multiscale composite containing hybrid fillers in the matrix.