Creep-fatigue interaction in composite materials

A novel phenomenological model taking into account the creep-fatigue interaction in composite materials’ fatigue performance is introduced in this paper. The model is based on the derivation of a master curve by using existing experimental fatigue data from a wide range of composite laminates and adhesively bonded composite joints. The developed model can subsequently be used in order to predict the fatigue behavior of additional composite materials systems under different loading conditions (stress ratios) when a limited amount of fatigue data is available. The model predictions were validated by comparisons to experimental data and relevant predictions provided by other existing models from the literature

Evaluation of the effect of granulation processing parameters on the granule properties: Lactose- Cornstarch case study

Understanding the relationship between processing parameters of fluidized bed wet granulation and the characteristics of intermediate and final products is crucial in the pharmaceutical processes. This research examined a fluidized bed wet granulation process containing a cornstarch solution as binder and lactose particles as powder. The design of experiment (DoE) was performed according to an L9 Taguchi method with three replications. The variables considered in the experimental design were binder flow rate, drying air temperature, spraying pressure, and initial mass of particle. The physical properties of the granules were evaluated in terms of granule mean size and granule size uniformity. A predictive model for each individual response was proposed. In addition, optimum conditions for each response were also obtained. Finally, the effect of the granule mean size on the flowability of granules was also investigated

Bubble splitting in a pseudo 2-D gas–solid fluidized bed for Geldart B type particles

Bubble splitting in 2D gas-solid freely bubbling fluidized beds is experimentally investigated using digital image analysis. The quantitative results can be applied for the development of a new breakage model for bubbly fluidized beds, especially discrete bubble models. The variation of splitting frequency with bubble diameter, new resulting bubble volumes, positions, and also the assumptions of mass and momentum conservation for bubbles after breakage are studied in detail. Small bubbles are found to be more stable than large ones and nearly all mother bubbles split into two almost equally sized daughter bubbles. The momentum of gas bubbles in the vertical direction remains approximately constant after breakage, whereas that of bubbles in the horizontal direction changes with no clear trend. The effect of fluidizing gas velocity in breakage frequency is also examined

Effects of load interruption on the fatigue life of GFRP composites

The effect of cyclic loading interruption on the fatigue behavior of angle-ply (±45)2S glass/epoxy composite laminates was investigated by comparing the obtained results of continuous- and interrupted loading patterns. Continuous fatigue experiments were performed by applying a sinusoidal cyclic loading pattern with maximum cyclic stresses at six different stress levels. For interrupted fatigue experiments, the cyclic loading was interrupted for two hours at regular intervals, corresponding to 20% of the fatigue life under continuous loading at the same maximum cyclic stress level. It was observed that the distribution and the severity of the fatigue damage was a function of loading pattern and stress level. Damage was more uniform when interrupted fatigue loading was applied. This loading pattern decelerated damage growth and increased the specimen’s capacity to accumulate damage. The specimens loaded under interrupted fatigue exhibited longer fatigue lives than those continuously loaded. This enhancement of fatigue was more pronounced at high stress levels

Synthesis and characterization of cost-effective and high-efficiency biochar for the adsorption of Pb2+ from wastewater

Abstract This study aimed to investigate the adsorption mechanism of Pb2+ in wastewater using activated carbon derived from inexpensive materials, specifically avocado, bitter orange, and walnut leaves, through a single-step chemical activation process. The activated carbon was prepared using sulfuric acid as an activator, with a particle size of 1 mm. The pyrolysis reactor (slow-pyrolysis) operated at 600 °C for 90 min with a nitrogen flow rate of 5 L/min. Batch experiments were conducted under various conditions to determine the optimal dosage (1.5 g/L), equilibrium contact time (180 min), and pH (6.5). The study focused on employing cost-effective and highly efficient adsorbents, namely biochar produced from tree leaves, for the adsorption process. The results indicated that the pseudo-second-order kinetic model accurately described the adsorption process, while the Freundlich isotherm model best fit the experimental data. These findings suggest that tree leaves can serve as cost-effective and efficient adsorbents for a wide range of applications. Furthermore, multiple adsorption factors were evaluated in batch mode, including contact duration, pH, adsorbent dosage, concentration of the Pb2+ solution, and temperature. The maximum adsorption capacities for the activated carbon derived from avocado, bitter orange, and walnut leaves were found to be 60.46, 59.42, and 58.48 mg/g, respectively. Thus, this study highlights the effectiveness and economic feasibility of using pyrolysis-derived activated carbon from low-cost materials for the removal of Pb2+ from wastewater

Synergistic degradation of Congo Red by hybrid advanced oxidation via ultraviolet light, persulfate, and hydrodynamic cavitation

In the present study, hybrid activation of sodium peroxydisulfate (PS) by hydrodynamic cavitation and ultraviolet radiation was investigated for Congo Red (CR) degradation. Experiments were conducted using the Box-Benken design on inlet pressure (2–6 bar), PS concentration (0–50 mg. L−1) and UV radiation power (0–32 W). According to the results, at the optimum point where the pressure, PS concentration and UV radiation power were equal to 4.5 bar, 30 mg. L−1 and 16 W respectively, 92.01% of decolorization was achieved. Among the investigated processes, HC/UV/PS was the best process with the rate constant and synergetic coefficient of 38.6 × 10−3 min−1 and 2.76, respectively. At the optimum conditions, increasing the pollutant concentration from 20 mg. L−1 to 80 mg. L−1 decrease degradation rate from 92.01 to 45.21. Presence of natural organic mater (NOM) in all concentrations inhibited the CR degradation. Quenching experiments revealed that in the HC/UV/PS hybrid AOP free radicals accounted for 63.4% of the CR degradation, while the contribution of sulfate (SRs) and hydroxyl radicals (HRs) was 53.1% and 46.9%, respectively

Effect of Loading Pattern on Fatigue Behavior of Laminated Composites

The effect of load interruptions on the fatigue behavior of (±45)2s angle-ply glass/epoxy composite laminates was investigated in this work. Constant amplitude fatigue experiments were performed at different stress levels to derive base line fatigue data. In addition, interrupted-fatigue experiments were performed by removing the cyclic loading for two hours repetitively, after cycling for 20% of the fatigue life achieved under continuous loading at the same maximum cyclic stress level. The specimens loaded under interrupted fatigue exhibited longer fatigue live than those continuously loaded until failur