Hydrothermal Ageing Effect on Reinforcement Efficiency of Nanofibrillated Cellulose/Biobased Poly(butylene succinate) Composites

Nanofibrillated cellulose (NFC) is a sustainable functional nanomaterial known for its high strength, stiffness, and biocompatibility. It has become a key building block for the next-generation of lightweight, advanced materials for applications such as consumer products, biomedical, energy storage, coatings, construction, and automotive. Tunable and predictable durability under environmental impact is required for high performance applications. Bio-based poly (butylene succinate) (PBS) composites containing up to 50% NFC content were designed and aged in distilled water or at high relative humidity (RH98%). PBS/NFC composites are characterized by up to 10-fold increased water absorption capacity and diffusivity and the data are correlated with model calculations. Aged samples exhibited decreased crystallinity and melting temperature. Incorporation of NFC into PBS showed up to a 2.6-fold enhancement of the elastic modulus, although accompanied by a loss of strength by 40% and 8-fold reduction in the strain at failure of maximally loaded composites. Hydrothermal ageing had almost no influence on the tensile characteristics of PBS; however, there were considerable degradation effects in PBS/NFC composites. Altered reinforcement efficiency is manifested through a 3.7-fold decreased effective elastic moduli of NFC determined by applying the Halpin–Tsai model and a proportional reduction of the storage moduli of composites. The adhesion efficiency in composites was reduced by hydrothermal ageing, as measured Puckanszky’s adhesion parameter for the strength, which decreased from 3 to 0.8. For the loss factor, Kubat’s adhesion parameter was increased by an order. PBS filled with 20 wt.% NFC is identified as the most efficient composition, for which negative environmental degradation effects are counterbalanced with the positive reinforcement effect. The PBS matrix can be used to protect the NFC network from water.

Influence of Carbon Black/Silica Hybrid Ratio on Properties of Passenger Car Tire Sidewall

Influence of carbon black (CB)/precipitated silica (SiO2) hybrid ratio on properties of a passenger car tire (PCT) sidewall based on natural rubber (NR) and butadiene rubber (BR) blend was investigated. Rubbers filled with various hybrid filler ratios at a constant loading of 50 phr were prepared and tested. The filler reinforcement efficiency in association with crucial properties of the tire sidewall were of interest. Results show the enhanced rubber–filler interaction with increasing SiO2 fraction leading to the improvement in many vulcanizate properties including hardness, tensile strength, tear strength and fatigue resistance, at the expense of cure efficiency and hysteretic behaviors (i.e., reduced heat build-up resistance and increased dynamic set). The results also suggest the improvement in tire sidewall performance of the NR/BR vulcanizates reinforced with CB/SiO2 hybrid filler, compared to that of the CB-filled vulcanizate.

Analysis of reinforcement efficiency and microscopic characterization of glass and carbon roving geometry in prestressed concrete composites

In this work, the reinforcement efficiency of concrete composites prestressed with glass and carbon rovings was studied. Prestressed concrete composites samples were prepared at a prestress level one-third the maximum tensile strength of the roving. The flexural properties of the manufactured composites were determined using a four-point bending test. Additionally, changes in the cross-sectional shape of the reinforcing rovings in the initial and prestressed states were analyzed using CT scanning and optical microscopy. The results showed that prestressing significantly affected the flexural properties of the concrete composites. Thus, the limit of proportionality increased by 1.26 and 1.85 for a composite reinforced with glass and carbon roving, respectively. The maximum flexural strength increased by approximately 1.2 times for both reinforcing rovings. The change in the cross-sectional shape of the reinforcing roving during prestressing enhances the efficiency of prestressed concrete composites.

Experimental research on effect of opening configuration and reinforcement method on buckling and strength analyses of spar web made of composite material

This study experimentally investigates the effect of the opening configuration on the buckling stability and bearing performance of a structural beam web used in a commercial aircraft made of composite materials. The buckling and strength analyses on three opening configurations (circular, oblong, and rhombic) were carried out using test samples with identical web surface size. It is found that the rhombic opening has the minimum effect on the buckling stability and strength of the structure. To compensate for the effect of the opening, two reinforcement methods, using reinforcement rib and thickening the sample, were also investigated in this study. It is concluded that thickening the sample can more effectively improve the buckling stability and strength performance of beam web structure and hence has relatively higher structural reinforcement efficiency.

Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams

Rigid low-density closed-cell polyurethane (PU) foams are widely used in both thermal insulation and structural applications. The sustainability of PU foam production can be increased by using bio-based components and fillers that ensure both enhanced mechanical properties and higher renewable material content. Such bio-based foams were produced using polyols derived from rapeseed oil and microcrystalline cellulose (MCC) fibers as filler. The effect of MCC fiber loading of up to 10 wt % on the morphology, tensile stiffness, and strength of foams has been evaluated. For estimation of the mechanical reinforcement efficiency of foams, a model allowing for the partial alignment of filler fibers in foam struts was developed and validated against test results. It is shown that although applying MCC fibers leads to modest gains in the mechanical properties of PU foams compared with cellulose nanocrystal reinforcement, it may provide a higher content of renewable material in the foams.

Сравнительный анализ эффективности углеродных нанотрубок и графена в армированнии полимерных нанокомпозитов

The comparative analysis of reinforcement efficiency (modulus of elasticity enhancement) of polymers with carbon nanotubes and grapheme was performed using the methods of fractal analysis and percolation theory. It has been shown that such comparison is correct only at the same structure of the indicated anisotropic nanofillers in polymer matrix. For carbon nanotubes reinforcement efficiency depends strongly on their geometry, i.e. length and outer diameter. In addition the main role in polymers reinforcement play not initial characteristics of nanofiller, but its structures, obtained in production process of nanocomposites. In technological aspect carbon nanotubes are more suitable for manufacture of high-modulus nanocomposites, that is due to possibility of simple enough realization of their orientation.

The Cut Span Effect on the Beams Inclined Sections Strength Reinforced with External Composite Reinforcement

The article presents the studies’ results of the oblique sections strength of 24 reinforced concrete beams, reinforced by three-sided U-shaped carbon fiber collars. The impact of the span section is estimated as 1.5h0 2,0h0 and 2,5h0 on the beams’ composite reinforcement efficiency in the initial inclined cracks presence and absence.