This paper presents an experimental study on the behavior of sandwich beams made of green materials for both core and skin components. A unidirectional flax fabric and a partial bio-based epoxy were ...used to make fiber-reinforced polymer (FRP) skins and three flute varieties of corrugated cardboards (known as B, C, and BC flutes) with the bulk densities of 170, 127, and 138 kg/m3 were used for the core, respectively. A total of 30 small-scale sandwich beam specimens were manufactured across six unique beam varieties with dimensions of 50 mm in width, 25 mm in depth, and 200 and 350 mm in length (150 mm and 300 mm spans) and tested under four-point bending up to failure. Two failure modes of transverse indentation for the short specimens and longitudinal crushing of the core and skin for the long specimens were observed. The load-deflection, load-strain, and moment-curvature behaviors were analyzed to evaluate the strength and stiffness of the sandwich beam specimens. C flute with the lowest bulk density and the highest availability in the market amongst all the three flutes exhibited the highest strength and stiffness for sandwich applications. Overall, the corrugated cardboard cores combining with the flax FRP skins may be considered as a viable, green option for the fabrication of large-scale structural sandwich panels for building applications.
•Sandwich beams made of green materials were tested under bending.•Corrugated cardboards and bio-based flax composite skins were used.•Strength and stiffness of the sandwich beams were evaluated.•An analytical model considering nonlinearity of skins was developed.•It was concluded that corrugated cardboards can be considered a viable core material.
•Heterogeneous fuels involving polystyrene and corrugated cardboard considered.•Five distinct combustion stages of the heterogeneous fuel identified.•Vertical pyrolysis length, mass loss rate, and ...temperature profile analyzed.•A new method for calculation of the heterogeneous fuels B number proposed.•The flammability of the heterogeneous fuels quantified by the calculated B number.
This study investigates the flame spread behavior of heterogeneous fuels involving polystyrene and corrugated cardboard, using a measured B number to characterize the flammability of the heterogeneous fuels. Investigations of flame spread and flammability have typically been limited to homogeneous solid fuels. However, the combustion of solid combustibles, for example, the warehouse commodities, is practically multi-fuel combustion, which has not yet been well quantified. Experiments are conducted by using 500 × 500 × 500 mm corrugated cardboard cartons, which are compartmentalized into 125 cells and filled with 125 polystyrene cups. The flame spread behavior, the mass loss rate, vertical pyrolysis length, and temperature profile have been measured and analyzed. Five distinct combustion stages are identified. Experimental results show that the first three stages are primarily the combustion of the first column cells and the latter two stages are the combustion of the second column cells. The five-stage combustion process is performed circularly until the burn out of the whole carton. A new method is proposed to estimate the combustion area on internal surface based on the measured temperature profile. By using the measured parameters as well as the estimated combustion area on internal surface, the heterogeneous fuel B numbers for the first three stages are further calculated to quantify the flammability. The average B number of stage 3, during which the combustion of inside polystyrene cups is started, is calculated to be 3.53. By comparing with the B number of single polystyrene or corrugated cardboard, the flammability is increased due to the mixing of polystyrene and corrugated cardboard. The determination of a specific B number is beneficial for the flammability evaluation of heterogeneous fuels.
The corrugated board packaging industry is increasingly using advanced numerical tools to design and estimate the load capacity of its products. This is why numerical analyses are becoming a common ...standard in this branch of manufacturing. Such trends cause either the use of advanced computational models that take into account the full 3D geometry of the flat and wavy layers of corrugated board, or the use of homogenization techniques to simplify the numerical model. The article presents theoretical considerations that extend the numerical homogenization technique already presented in our previous work. The proposed here homogenization procedure also takes into account the creasing and/or perforation of corrugated board (i.e., processes that undoubtedly weaken the stiffness and strength of the corrugated board locally). However, it is not always easy to estimate how exactly these processes affect the bending or torsional stiffness. What is known for sure is that the degradation of stiffness depends, among other things, on the type of cut, its shape, the depth of creasing as well as their position or direction in relation to the corrugation direction. The method proposed here can be successfully applied to model smeared degradation in a finite element or to define degraded interface stiffnesses on a crease line or a perforation line.
The protection and maintenance of environmental resources for future generations require responsible interaction between humans and the environment in order to avoid wasting natural resources. ...According to an ancient Native American proverb, “We do not inherit the Earth from our ancestors; we borrow it from our children.” This indigenous wisdom has the potential to play a significant role in defining environmental sustainability. Recent technological advances could sustain humankind and allow for comfortable living. However, not all of these advancements have the potential to protect the environment for future generations. Developing societies and maintaining the sustainability of the ecosystem require appropriate wisdom, technology, and management collaboration. This book is a collection of 19 important articles (15 research articles, 3 review papers, and 1 editorial) that were published in the Special Issue of the journal Sustainability entitled “Appropriate Wisdom, Technology, and Management toward Environmental Sustainability for Development” during 2021-2022.addresses the policymakers and decision-makers who are willing to develop societies that practice environmental sustainability, by collecting the most recent contributions on the appropriate wisdom, technology, and management regarding the different aspects of a community that can retain environmental sustainability.
In the present work, an analytical equation describing the plate torsion test taking into account the transverse shear stiffness in sandwich plates is derived and numerically validated. Transverse ...shear becomes an important component if the analyzed plate or shell is thick with respect to the in-plane dimensions and/or its core has significantly lower stiffness than the outer faces. The popular example of such a sandwich plate is a corrugated cardboard, widely used in the packaging industry. The flat layers of a corrugated board are usually made of thicker (stronger) material than that used for the corrugated layer, the role of which is rather to keep the outer layers at a certain distance, to ensure high bending stiffness of the plate. However, the soft core of such a plate usually has a low transverse shear stiffness, which is often not considered in the plate analysis. Such simplification may lead to significant calculation errors. The paper presents the generalization of the Reissner’s analytical formula, which describes the torsional stiffness of the plate sample including two transverse shear stiffnesses. The paper also presents the implementation of the numerical model of the plate torsion test including the transverse shear stiffnesses. Both approaches are compared with each other on a wide range of material parameters and different aspect ratios of the specimen. It has been proved that both analytical and numerical formulations lead to an identical result. Finally, the performance of presented formulations is compared with other numerical models using commercial implementation of various Reissner–Mindlin shell elements and other analytical formulas from the literature. The comparison shows good agreement of presented theory and numerical implementation with other existing approaches.
Corrugated cardboard (CCB) was pyrolyzed at different temperatures (350, 400 and 450 °C) to produce biochar fibers. The biochar and CCB control fibers were then compounded with high density ...polyethylene (HDPE) and maleated polyethylene (MAPE) to prepare wood plastic composites (WPC). The effect of different pyrolysis temperature biochars on the WPC's mechanical, thermal and viscoelastic properties, water absorptions, rheological behavior, weatherability and biodurability performance were evaluated. The CCB composite melts showed higher modulus and viscosity than biochar composites, indicating better melt strength. Compared with CCB composites, an increase of tensile strength (4%) and tensile modulus (30%) could be observed in composites made from CCB 350 °C biochar. In addition, the CCB biochar composite showed lower tan δ and adhesion factor, indicating the strong interfacial interaction between biochar fibers and HDPE. The composite melting temperatures (Tm) were not significantly different. The degree of HDPE crystallinity in the biochar composites decreased relative to the CCB composites, while the thermal properties of the composites improved compared with CCB composites. The CCB composite displayed the highest water absorption (3.9%) and thickness swell (3.8%) after 70 d. The CCB biochar (450 °C) composite experienced the least color change, lightless and carbonyl concentrations due to weathering. Pyrolysis of CCB reduced weight loss in the resulting composites exposed to fungi compared with the CCB composite. Using CCB biochar led to a more biodurable WPC.
•This study compared cardboard and cardboard biochar fibers for use in HDPE composites.•Biochar fibers improved composite mechanical properties, dimensional stability, photostability and biodurable properties.•CCB350 composite showed the best mechanical properties.•CCB400 composite showed the best dimensional stability.•CCB450 composite showed the best photostability and biodurability against fungal attack.
The optimal selection of the composition of corrugated cardboard dedicated to specific packaging structures is not an easy task. The use of lighter boards saves material, but at the same time ...increases the risk of not meeting the guaranteed load capacity. Therefore, the answer to the question "in which layer the basis weight of the paper should be increased?" is not simple or obvious. The method proposed here makes it easy to understand which components and to what extent they affect the load-bearing capacity of packages of various dimensions. The use of numerical homogenization allows for a quick transformation of a cardboard sample, i.e., a representative volume element (RVE) into a flat plate structure with effective parameters describing the membrane and bending stiffness. On the other hand, the use of non-local sensitivity analysis makes it possible to find the relationship between the parameters of the paper and the load capacity of the packaging. The analytical procedures presented in our previous studies were used here to determine (1) the edge crush resistance, (2) critical load, and (3) the load capacity of corrugated cardboard packaging. The method proposed here allows for obtaining a comprehensive and hierarchical list of the parameters that play the most important role in the process of optimal packaging design.
The standard edge crush test (ECT) allows the determination of the crushing strength of the corrugated cardboard. Unfortunately, this test cannot be used to estimate the compressive stiffness, which ...is an equally important parameter. This is because any attempt to determine this parameter using current lab equipment quickly ends in a fiasco. The biggest obstacle is obtaining a reliable measurement of displacements and strains in the corrugated cardboard sample. In this paper, we present a method that not only allows for the reliable identification of the stiffness in the loaded direction of orthotropy in the corrugated board sample, but also the full orthotropic material stiffness matrix. The proposed method uses two samples: (a) traditional, cut crosswise to the wave direction of the corrugated core, and (b) cut at an angle of 45°. Additionally, in both cases, an optical system with digital image correlation (DIC) was used to measure the displacements and strains on the outer surfaces of samples. The use of a non-contact measuring system allowed us to avoid using the measurement of displacements from the crosshead, which is burdened with a large error. Apart from the new experimental configuration, the article also proposes a simple algorithm to quickly characterize all sought stiffness parameters. The obtained results are finally compared with the results obtained in the homogenization procedure of the cross-section of the corrugated board. The results were consistent in both cases.
Three types of wood pulp feedstocks including bleached softwood kraft, unbleached softwood kraft and old corrugated containers were disk refined to produce cellulose nanofibrils at different fineness ...levels ranging from 50 to 100%, and the resulting aqueous suspensions of cellulose nanofibrils were spray dried. The spray drying experiments were carried out to examine different processing conditions for the different CNF feedstock types and fines level at various suspension concentrations to produce dry samples with free-flowing powder morphologies. The fineness levels and solids contents of CNF suspensions were set to 80% or more and 1.8% or less, respectively. If the solids content of the CNF solutions was high and the fibrillation level was low, plugging was experienced in the spray head because of the high viscosity of the suspensions, resulting in production of poor-quality powders. In terms of reduction in processing energy, even if the CNF suspension solids content was increased to 1.5 wt.%, the powder quality and the production yields were excellent. It was confirmed that high-quality powder under 20 µm were produced at a 90% fibrillation level of all CNF feedstocks. The resulting dry CNF powders were characterized to determine particle size distributions and morphological properties via a scanning electron microscope and a laser diffraction particle size analyzer. The particle sizes were smaller at higher fibrillation levels and lower solids content of the CNF suspensions. The CNF suspension derived from bleached kraft pulp, the average particle size decreased by 43% and 33% with the lowered solids contents from 1.8 to 1%, and the increased fineness levels from 80 to 100%, respectively.
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