جستجوی مقالات مرتبط با کلیدواژه « honeycomb » در نشریات گروه « مواد و متالورژی »

The needs of the human communities and industry to build low weight, high strength and durable structures have increased the demand for composite materials, including sandwich structures. In this case sandwich panels are used in situations requiring high mechanical strength, low weight, sound insulation and thermal insulation properties. In this study, carbon nanotubes-reinforced composite honeycomb sandwich panels, were constructed using silicone molding. To determine the role of carbon nanotubes on the compressive and bending behavior of sandwich panels, a different weight percentage of this material (0/025, 0/05. 0/075) was added to the epoxy resin. Also, different thicknesses (5mm, 2/5mm) were tested to determine the role of core wall thickness on the compressive and bending behavior of sandwich panels. The results showed that the compressive strength of honeycomb panels has a direct relation with the increase in the percentage of carbon nanotubes and also the thickness of the wall. The Compressive strength of Sandwich panels increased from 42/06 up to 54/32 MPa with increasing carbon from 0/025 up to 0/075 nanotubes. The compressive strength of sandwich panels with 5 mm honeycomb wall thickness and reinforced with 0/025, 0/05 and 0/075 weight percent of carbon nanotubes compared to sandwich panels with 2.5 mm honeycomb wall thickness were respectively 2/38, 2/15 and 2.17 times. also the flexural strength of 5-mm honeycomb wall thickness and reinforced with 025/0, 0/05 and 0.075% weight percent of carbon nanotubes compared to sandwich panels with 2.5 mm honeycomb wall thickness, were respectively 3, 2.66 and 2.7 times.

In this paper, high velocity impact behavior of honeycomb structures was modeled by implementing high strain rate dependent properties of honeycomb and its ballistic limit velocities in collision with hemispherical as well as flat ended projectiles were calculated. The obtained results were validated with those available in open literature and numerical ballistic limit velocities were found to be in good agreement with experimental ballistic limit velocities. In addition, ballistic limit velocities in models without strain rate dependent properties were calculated and compared with those in previous models to evaluate the influence of strain rate dependent properties. Comparing the results of these two kinds of models showed that using strain rate dependent properties increases absorbed energy as plastic dissipated and frictional dissipated energies which improve accuracy of numerical modeling significantly. On the other hand, fracture mechanisms and damaged zones were investigated in numerical models and were compared with experimental output. Damaged zones in front of honeycombs in numerical models were similar to experiments but honeycomb manufacturing process and random collision of projectile with honeycomb, made some differences in damaged zone at the back of the honeycombs.

Sandwich structures are used in applications that required a combination of high rigidity and low weight same as aerospace, marine and automotive. Large and/or complicated sandwich structures are often manufactured by connecting pre-fabricated sandwich panels by means of connections, adhesive or bolts. In present study, two types of metallic connections were used to join two sandwich panels with glass-epoxy face-sheets and aluminum honeycomb core. Connections have the same material and different geometries and were bonded to the sandwich structures using the same epoxy as used to manufacture the face-sheets. Two groups of specimens were made and tested under bending loading. Also, a finite element simulation using LS-DYNA were performed to predict the behavior of sandwich structures. A good compliance between numerical and experimental results was observed. The effects of increasing the length and the thickness of the connections on the maximum force and energy absorption were investigated to examine the influences of involved parameters on bending response of a sandwich plates.