Foam cores

Composites can be created ia which the core optimizes desired physical properties such as modulus, whereas the outer layer optimizes surface coasideratioas aot inherent ia the core material. SoHd outer—foam core can provide composites with significant reductions ia specific gravity (0.7). Dry blowiag ageats can be "dusted" onto the peUets orHquid agents iajected iato the first transitioa sectioa of the extmder. 

Pipe and fittings remain a significant market for ABS, particularly in North America. ABS foam core technology allows ABS resin to compete effectively with PVC in the primary drain-waste and vent (DWV) pipe market. 

An example of the contribution of polar interactions between an acrylic PSA and a substrate is shown in Fig. 6. By copolymerizing iso-octylacrylate and acrylic acid, using a monomer ratio of, respectively, 95/5 and 90/10, two otherwise identical PSAs were made. The PSAs were laminated to both sides of a foam core to make an attachment tape as used in the automotive industry for the application of body side moldings to a car. One side of the foam tape was laminated against an aluminum foil backing. The other side was laminated against an automotive paint-coated panel to make the final test sample. The test sample was allowed to... 

Fig. 16. Extensive deformation of foam core during debonding.

Adhesives for sandwich bonding progressed similarly. Early low-flow adhesives were used with plastic foam cores and end-grain balsa to manufacture sandwich as.semblies. The development of less dense honeycomb cores necessitated a change in adhesive. Development of good bond strength to honeycomb core requires relatively high flow so that an adhesive fillet forms on the core walls (Fig. 6). 

It is becoming common practice to have the cross-section of a plastic moulding made up of several different materials. This may be done to provide a permeation barrier whilst retaining attractive economics by having a less expensive material making up the bulk of the cross-section. To perform stress analysis in such cases, it is often convenient to convert the cross-section into an equivalent section consisting of only one material. This new section will behave in exactly the same way as the multi-layer material when the loads are applied. A very common example of this type of situation is where a solid skin and a foamed core are moulded to provide a very efficient stiffness/weight ratio. This type of situation may be analysed as follows ... 

Example 2.8 A polypropylene sandwich moulding is 12 mm thick and consists of a foamed core sandwiched between solid skin layers 2 mm thick. A beam 12 mm wide is cut from the moulding and is subjected to a point load, IV, at mid-span when it is simply supported over a length of 200 mm. Estimate the depth of a solid beam of the same width which would have the same stiffness when loaded in the same way. Calculate also the weight saving by using the foam moulding. The density of the solid polypropylene is 909 kg/m and the density of the foamed core is 6(X) kg/m. ... 

A rectangular section beam of solid polypropylene is 12 mm wide, 8 mm deep and 300 mm long. If a foamed core polypropylene beam, with a 2 mm solid skin on the upper and lower surfaces only, is to be made the same width, length and weight estimate the depth of the composite beam and state the ratio of the stiffness of the two beams, (p = 909 kg/m, p = 500 kg/m ). 

Compare the flexural stiffness to weight ratios for the following three plastic beams, (a) a solid beam of depth 12 nun, (b) a beam of foamed material 12 mm thick and (c) a composite beam consisting of an 8 mm thick foamed core sandwiched between two solid skin layers 2 mm thick. The ratio of densities of the solid and foamed material is 1.5. (hint consider unit width and unit length of beam). 

This type of analysis could also be used for a sandwich structure with solid skins and a foamed core. It is simply a matter of using the appropriate values of E, G 2,Ei,v 2 for the skin and core material. This is illustrated in the following Example. 

A composite of gfrp skin and foamed core is to have a fixed weight of 200 g/m. If its width is 15 mm investigate how the stiffness of the composite varies with skin thickness. The density of the skin material is 1450 kg/m and the density of the core material is 450 kg/m. State tte value of skin thickness which would be best and for this thickness calculate the ratio of the weight of the skin to the total composite weight. 

In addition to developing solid RP structures, work has been conducted on sandwich structures such as filament-wound plastic skins with low-density foamed core or a plastic honeycomb core to develop more efficient strength-to-weight structures. Sandwich structures using a syntactic core have been successfully tested so that failures occurred at prescribed high-hydrostatic pressures of 28 MPa (4,000 psi). 

The chassis is made from a 1/4 in. sheet of either ABS or TPO vacuum formed into a tub and reinforced with reinforced pultruded glass fiber-TS polyester plastic tubing. The hood and other products are being made from a 20 mm thick sandwich of thermo-formed PPO-alloy skins, glass fabric infused with thermosetting vinyl ester, and a urethane foam core. The bumper and front fascia is thermoformed from a polyolefin elastomer sheet with an UV-resistant cap layer of DuPont s Tediar PVF film. The dash and... 

Quadraxially oriented (four directional layer) glass fabric-TS vinyl ester polyester RP sheet panels with a foam core and gel coating are used. Most of the panels are 3 mm thick with molded-in rib structure supports. Body skins are bonded to the chassis with a double-stick acrylic tape developed by 3M Co. as well as mechanical fasteners. Unlike most steel designs, no B-pillar structural component between the front and rear doors is required thus providing more interior space and easy entry since doors open in opposite directions. 

The composite cross-section of a SF product contains an ideal distribution of material, with a solid skin and a foamed core. The... 

Frontages in sandwich made of PVC foam core and skins of fire-resistant glass fibre reinforced polyester. The panels are attached onto a steel framework. 

Multimaterial parts can be processed with, for example, a foamed core of recycled material and a dense skin made of the same virgin material. 

Figure 6.11. Schematic principle of a sandwich composite with a foamed core...

Seats made of sandwich composite with foamed core and thermoplastic skins. 

Styrene-acrylonitrile foam Core-Cell by ATC Chemicals... 

Syntactic foams are obtained by mixing hollow micro- or macro-balloons, generally made of glass but sometimes of polymer, directly with a liquid resin, generally a thermoset. Some extend this definition to all composites with a foamed core. 

Good compression properties for cores made of honeycombs, wood and plywood. Low compression properties for foamed cores. The compression strength and modulus of a lOOkg/m foam are roughly as low as 2 MPa and 0.1 GPa, respectively. On the other hand, pinpoint impact is distributed across the whole surface facing, provided it is sufficiently resistant. 

By application of this equation for a facing thickness of 0.5 (t = 0.5), Figure 6.21 shows the ratio of DI Ef>) for a sandwich panel toDI(Efb) for the facings without foam, as a function of the foam core thickness. Note that rigidity can be multiplied by 50 for a core thickness of 3.6, that is to say, a panel thickness of 4.6 and a practically unchanged weight. 

The MDB is a two-story, steel-framed building with thick, reinforced-concrete floors and most interior walls made of concrete and foam-core sandwich panels. Explosion containment rooms have 2-foot-thick reinforced concrete floors, walls, and ceilings. Because concrete is a porous material capable of absorbing agent, all concrete surfaces in the JACADS process areas were sealed with an epoxy coating. A total of 134,153 square feet of concrete will require decontamination (U.S. Army, 1999d). 

The thermal conductivity of a section of a commercially produced high density polyethylene foam channel was measured. The walls consisted of a 6.4 mm foam core with a skin of 1.6 mm thickness on either side. Sqnares were machined from the outer surface of the channel, so that heat flow throngh the entire thickness the core pins one skin layer and the complete section conld be... 

These essentially comprise a mixture of a skin-forming component, which comprises two distinct phases blended together, a high zero-shear viscosity material and a low zero-shear viscosity material, and a foam core-foaming component, which includes a blowing agent, physically dry blended together. The three materials are preferably selected from suitable homopolymers and copolymers of ethylene. CANADA... 

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