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What is N ida- C ore Rigid- E lastic T echnology?

P olypropylene is a thermoplastic polymer with centerline of an I-beam, low-density core materi- Visco-elastic properties. Bee-developed honey- als are used throughout the space between two comb in hexagonal form is one of the most effi- skins. The following schematic demonstrates the cient structures found in nature. Using complex effectiveness of a honeycomb panel (Al) com- processing techniques, a proprietary co-polymer pared to a solid aluminum sheet in 1/4-inch thick- compound of polypropylene can be formed into ness. By using a core material to double the thick- honeycomb panel stock, resulting in a structure ness, the flexural stiffness is increased seven (7) with exceptional specific rigidity (stiffness to weight) times at almost the same weight! The mechanical and energy absorption, while incorporating the material benefits of visco-elasticity. Composite sandwich panel constructions using Nida-Core Honeycomb are the realization of this RIGID-ELASTIC TECHNOLOGY . Honeycombs can be constructed with many dif- ferent materials. The most common method of fabrication is adhesive bonding flat sheets of ma- terial with offset lines of adhesive, and subse- quently expanding them to open the cells. This technique is commonly used to used fabricate honeycomb from paper or aluminum products. By contrast, honeycombs may be constructed from
Note: Skin thickness is the same for all examples and overall thickness doubles. thermoplastic materials by extruding profiles through a die and then joining them by thermal fusion to form large blocks, which eliminates the efficiency of this cored sandwich can be dramati- need for industrial adhesives. Regardless of the method cally increased by increasing core THICKNESS. used, sheet stock can be cut from the large blocks Core materials have one or more intrinsic proper- of honeycomb in the same fashion as foam or ties that are advantageous for specific applica- end-grain balsa. However, the sheet stock cut tions, and these properties must be carefully con- from the extruded profiles will possess mechanical sidered when designing composite structures. Just properties in the longitudinal and transverse direc- as composite laminates have specific properties tions of the core that differ from the properties of determined by the selected reinforcements adhesively bonded and expanded honeycombs. and matrix resins, sandwich panels take on many Extruded honeycombs, such as Nida-Core H8 PP, additional characteristics that are uniquely deter- have equal properties in either axis. mined by the selected core material. Distinguish- Although the use of sandwich construction in ma- ing materials by their respective limitations, includ- rine applications often has been the subject of ing strain-to-failure, is as important for core as it is debate, the problems that stimulate the debates for fibers and resins. Elasticity has been an essen- are typically traceable to early boat designs tial issue in the debate concerning the risks of intro- that employed inadequate building methods or ducing brittle fibers like carbon, or opting for the specified the wrong core material for the engi- damage tolerance provided by aramid fibers, neered load. These isolated incidents, however, such as Kevlar. When it comes to core material, it are not the norm. The great majority of sandwich is also helpful to compare characteristics in rela- constructed boats have performed well over the tion to elasticity and damage tolerance. Of the years. Why is honeycomb sandwich panel con- commonly used core materials, balsa and alumi- struction used? The primary reason is to maximize num honeycomb are among the least elastic. the mechanical efficiency of structures to save Polymeric foams demonstrate a wide range of weight and raw materials. Sandwich panels mimic properties, depending on their specific formula- the characteristics of an I-beam, using flanges to tions and densities. In general, thermoset polymers support tensile and compression loads, with a are less elastic than thermoplastics. Urethane- shear web joining the flanges. Composite skins based foams are thermoset, and are the least constitute the flange portions of the I-beam. In- elastic of the polymeric foams. PVC foams dem- stead of using narrow webs, as is done on the onstrate a wide range of elasticity, from blended

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