Sandwich structures with carbon fiber-epoxy face sheets and polyvinyl chloride foam core material are known for their high strength and flexural stiffness despite their low weight. However, the structural response, in terms of crush strength, of the particles added sandwich structures are not very well known under impact loading conditions. In this study, the impact resistance and damage characteristics of particle added low weight composite sandwich structures were investigated with a low-velocity drop weight impact test device. Boron carbide (B 4 C) particles, which had excellent hardness, thermoelectric, and radiation absorbing characteristics, were used as an additive for the epoxy matrix. For this purpose, 2%, 5%, and 10% by weight additives were mixed into the epoxy matrix and sandwich structures were produced with hand lay-up followed by vacuum bagging method. All configurations were subjected to low-velocity drop weight impact test at three different energy levels (10, 17.50, and 25 J). The results obtained from the experiments and the images of the post-impact damage of the sandwich structures were presented comparatively. According to the test results, configurations containing 10% boron carbide (B 4 C) additive has shown the best performance in terms of resistance to impact load. K E Y W O R D S boron carbide (B 4 C) particles, carbon fiber reinforced polymer (CFRP), epoxy matrix modifying, low-density PVC foam core sandwich structures, low-velocity impact properties, radiation shielding barriers

Composite materials are the combination of two or more materials to achieve certain improved or desired properties. And construction of the composite material can be performed by using a continuously distributed medium called as matrix. Metals, ceramic, glass and polymer materials are commonly used as matrix. The reinforcing material can be a metal, ceramic, glass, textile, polymer, or organic material in the form of lamina, fiber (short and long), particle, whisker, etc. Composite materials have emerged as a major class of structural elements due to their benefits such as lightweight, flexible, good impact strength, improved fatigue strength, high corrosion resistance, etc. Because of these advantages, composite materials are considered as a replacement of traditional materials which are used in the fields of aerospace, automotive, and other industries [1,2].

In this study, a generative method was introduced to determine the optimal design of low-density polymer foam core sandwiches using finite element analysis (FEA) and multi-objective optimization of design variables without needing experiments. The method was also assessed. The sandwich structures were designed based on woven plain carbon fiber fabrics, PVC foam core, and polymer epoxy matrix. The design variables are the core density (40, 48, 60 kg/m3) and the core thickness (16, 20, 25 mm). The sandwich configurations were subjected to FEA under the three-point bending (TPB) loads. The force-reaction curves obtained from FEA were compared to experimental data available in the literature. Excellent agreement was achieved between the experimental and FEA simulated results at the linear elastic region of the curves. Thus, it allowed predicting the bending stiffness of the sandwiches via TPB analysis. Besides, a two-way analysis of variance (ANOVA) was conducted to determine the effects of parameters on sandwich mass and bending load capacity. Multi-objective optimization of design variables was also carried out according to the constructed mathematical models. The method provided in this study eases both designer’s and researcher’s work to obtain the optimal design variables without making costly experiments.

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Today, the competitiveness of companies is directly dependent on the quality and price of their products. This is because consumers have more options to buy a product than in previous years. In this study, two different mathematical models are developed to determine the best product mix according to different constraints for a fruit nectar producer. For a fruit nectar producer, 4 main and 9 sub-quality criteria were entered into the mathematical models whose importance levels were determined by the analytic hierarchy process (AHP) method. These models, created for optimum product mix, consider not only the integrated quality criteria but also different constraints such as capacity, labor, and raw material. Models aiming at breakeven and maximum profit have been run for different scenarios such as consumer demands, machine maintenance, and the increase in bottlenecks. The results have shown that the quality criteria change the production efficiency and sales quantities, and how much the existing production system can adapt if consumer demands change.