“…In order to investigate the effect of the core sequence and its material type and the facesheet thickness on bending stiffness of the sandwich specimens, sandwich panels with different facesheet thicknesses and the core sequences must be model by FE code in the linear elastic region and for a small displacement to get the initial slope of the linear load–displacement curves as the specimen's stiffness. [ 46–48 ] As observed by the present experiments, the linear portion of various sandwich specimens in bending tests were around the displacement of 2.5–3 mm. So, for more conservative situation and accurate results, FE analysis were conducted up to the displacement of 2 mm, and the slope of this linear portion were considered as bending stiffness of the specimens.…”
In this research, the flexural behavior of lightweight biodegradable sandwich panel consisting of the outer green composite facesheets with polylactic acid (PLA) matrix and natural kenaf and cotton fibers, with five various stacking types of standard cardboard egg boxes cores under three-point bending loads as an environmentally friendly alternative to conventional synthetic sandwich structures is investigated. The stiffness of this structure in bending is also studied using finite element simulations. The thickest specimen absorbed the most energy during flexural testing, however, the specimens containing two egg boxes inside each other were found to have a higher strength and stiffness. Using finite element method simulations to investigate the influence of composite facesheet thickness on flexural loads, it was found that the amount of the load carried by each sandwich specimen with doubled thickness was increased at least by about 50%. By changing the core's material from cardboard egg box to bamboo/PLA or kenaf-cotton/PLA egg boxes, stiffness and strength and also the energy absorption were significantly increased. Therefore, it is possible to fabricate composite sandwich structures which are light and biodegradable for green environment and has the potential to replace many plastic products and structures that are used in food packaging and medium loads structures applications.
“…In order to investigate the effect of the core sequence and its material type and the facesheet thickness on bending stiffness of the sandwich specimens, sandwich panels with different facesheet thicknesses and the core sequences must be model by FE code in the linear elastic region and for a small displacement to get the initial slope of the linear load–displacement curves as the specimen's stiffness. [ 46–48 ] As observed by the present experiments, the linear portion of various sandwich specimens in bending tests were around the displacement of 2.5–3 mm. So, for more conservative situation and accurate results, FE analysis were conducted up to the displacement of 2 mm, and the slope of this linear portion were considered as bending stiffness of the specimens.…”
In this research, the flexural behavior of lightweight biodegradable sandwich panel consisting of the outer green composite facesheets with polylactic acid (PLA) matrix and natural kenaf and cotton fibers, with five various stacking types of standard cardboard egg boxes cores under three-point bending loads as an environmentally friendly alternative to conventional synthetic sandwich structures is investigated. The stiffness of this structure in bending is also studied using finite element simulations. The thickest specimen absorbed the most energy during flexural testing, however, the specimens containing two egg boxes inside each other were found to have a higher strength and stiffness. Using finite element method simulations to investigate the influence of composite facesheet thickness on flexural loads, it was found that the amount of the load carried by each sandwich specimen with doubled thickness was increased at least by about 50%. By changing the core's material from cardboard egg box to bamboo/PLA or kenaf-cotton/PLA egg boxes, stiffness and strength and also the energy absorption were significantly increased. Therefore, it is possible to fabricate composite sandwich structures which are light and biodegradable for green environment and has the potential to replace many plastic products and structures that are used in food packaging and medium loads structures applications.
“…During the loading process, the top layer of bamboo plywood was compressed and the bottom layer was in tension first. As the load increased, the former caused the local buckling of the top layer, while the latter led to the delamination between bamboo strips layer and the tensile failure of the bottom layer, resulting in the ultimate failure [25]. As shown in the Fig.…”
Section: Mechanical Properties and Fracture Patternsmentioning
confidence: 91%
“…It could be seen in Fig. 3 that the top layers of S2-5 and S2-8 were compressed and sheared, resulting in the separation of bamboo strips layers in pure bending region [25].…”
Section: Mechanical Properties and Fracture Patternsmentioning
The acoustic emission (AE) technique can perform non-destructive monitoring of the internal damage development of bamboo and wood materials. In this experiment, the mechanical properties of different bamboo and wood (bamboo scrimber, bamboo plywood and SPF (Spruce-pine-fir) dimension lumber) during four-point loading tests were compared. The AE activities caused by loadings were investigated through the single parameter analysis and K-means cluster analysis. Results showed that the bending strength of bamboo scrimber was 3.6 times that of bamboo plywood and 2.7 times that of SPF dimension lumber, respectively. Due to the high strength and toughness of bamboo, the AE signals of the two bamboo products were more abundant than those of SPF dimension lumber. However, the AE evolution trend of the three materials was similar, which all experienced three stages, including gentle period, steady period and steep period, and the area of rupture precursor characteristics could be recognized before the specimen destroyed. Due to the bottom layer was first tensile failure, the main structure of bamboo plywood was destroyed after the stress redistribution. The rupture precursor characteristics could be observed before each peak. Findings put in evidence a good correlation between AE clusters of two bamboo products, while the amplitude and energy of wood signals were lower than those of bamboo. The amplitude and energy from the propagation and aggregation of cracks were greater than those related to micro-cracks initiation.
“…The effects of various parameters such as core configurations, face sheets thickness, and initial imperfection on the behavior of sandwich panels were investigated. In an experimental study, Darzi et al [254] examined the bending strength and stiffness, shear strength, and core/face sheets interface of sandwich panels with plywood face sheets and bamboo/peeler cores. Recently, Oliveira et al [255] have developed novel bio-degradable sandwich panels in which flax fibers are used in the face sheets and bamboo rings as the core.Figure 14.Schematic of the bamboo core configurations in bamboo core sandwich panels [252].…”
Section: Sandwich Structures Made Of Non-wood Cellulose Natural Fibersmentioning
In recent years, concerns about environmental pollution have led to the development of natural fiber sandwich structures as alternatives to petroleum-based ones. This paper reviews various studies on sandwich structures composed of non-wood cellulose-nature fibers. These fibers mainly include flax, hemp, jute, kenaf, sisal, coir, and bamboo. The studies are classified based on the type of fibers, the components in which they are used, and experimental tests/numerical investigations. Furthermore, a few suggestions for future research in the field of eco-friendly sandwich structures are made.
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