Author: AKeson

A couple of design considerations

FRP Composites have their own special set of considerations in design and use. And we will discuss a few here. The traditional fiberglass (unsaturated polyester with glass reinforcement) uses gelcoat on the molded (decorated) side. This is really only one side of the part, as this is not a matched-mold process. So the back side needs to be hidden from view or covered with another material, etc. A boat, for example has a Deck and a Hull that are mated together so that the back sides of the parts are hidden from view. The inside of the cabin is then upholstered and trimmed out for comfort and decoration. I have worked with fiberglass tabletops before where the top side is gelcoated in a decorative finish and the edge wraps down and trimmed. All of the unsightly surfaces face the floor where they cannot be viewed. There are a few closed-mold processes that can be implemented, but these really only achieve a Class B surface out of the mold. With rework and repair, a Class A surface can be accomplished. I know of some folks that make Boat Access Hatches where they repair the backside (bottom) and rework it so it looks pleasant when opened. Molded-in features must be used with caution. Sharp edges must be avoided because the process hates having to get resin and reinforcement into them, and...

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Curing Mechanisms

Temperature plays an important role in the curing process of the resins used in composites. Many of the resins are setup for room-temperature curing. This requires that the ambient room temperature is ideally set between 65 and 75 degrees. And that the resin itself is near this temperature. academic thesis The old rule of thumb is that a drum of resin takes about 24 hours to get to room temp when moved in from shipping or storage. lowest price on levitra These room temperature cured resins have windows of open working time before the curing cycle begins to happen. Elevated temperatures in the summer can cause havoc, but can be managed with special mixtures and ingredients. Some resins cure with time and elevated temperatures, which are achieved with the use of ovens. These allow for nearly unlimited open working time before cure. When things are satisfactorily placed, the temperatures are elevated to start the cure process. UV Light is another curing mechanism that has special applications and takes the temperature consideration away. This has a big use with the infrastructure restoration industries working onsite and underground. It is much more of a specialized niche...

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Stiff to the core

The thickness of the laminate will affect its stiffness. Stiffness can be increased by adding structural supports to the backside of the laminate, such as bulkheads and stringers in a boat. Another way to increase stiffness while minimizing the weight of carrying a solid glass and resin cross section is to use a core material. Core materials are fairly wide ranging. They include wood; especially end-grain balsa and plywood. http://vva.org/blog/?p=3274 Plastics such as foamed PVC, foamed polyurethane, honeycombed polypropylene, and several others can be used with success. Paper honeycomb and cardboard can also be used with success in the proper application. The biggest key to successful core use is successful adhesion and capture of the coring material. It needs to be part of the laminate in order to be beneficial. Each material has their own downfall, and these must be considered for each application. Wood and paper rot if exposed to water. Some of the thermoplastics materials melt and deform under high temperatures. Some are too expensive. Plywood and Balsa have density ranges across the sheets, while plastics are much more controlled and consistent. Ideally the core material is placed directly in the center of the cross-section of the laminate so that the neutral axis passes in the center of the core material. This balances the loading forces of compression and tension under loading conditions from either side. The...

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Model and Sculpture

Composites have great effectiveness for creating low-volume and one-off production runs. A quick layup can be shaped over a rough foam carving before being sanded, smoothed, and painted. Autobody filler (Bondo) is shares the same chemistry as the polyester and vinylester resins and bonds very well to surfaces that are either just hitting cure stage or are sanded with sandpaper rougher than 80 grit. The range of shapes, details, and size are almost limitless from here. This is why fiberglass is very commonly used in Hollywood movie sets, amusement parks, and sculptures. These structures do need proper support from moving over time. Even if the structure is not meant to be weight-bearing they need to at least support themselves. There is some amount of thermal expansion that happens with temperature changes which can lead to crack development. The complexity of the geometry and thickness of the laminate are variables to consider when figuring howmuch additional support must be added. Building a frame with welded steel tubing or screwed dimensional lumber is one way to support a fiberglass structure. And another school of thought is to create supporting ribs with flat stock to hold the shape. Both of these supporting structures are commonly attached via resin and glass...

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Composites Overview

Composites processes are generally low cost with regards to tooling and equipment costs, depending upon what process is used viagra tabs for comparison. The flip side is that the processes are labor intensive and the quality is operator dependent. The room-temp cure resins allow for working time windows that must be monitored so that the work is complete before the resins get hard. It is one of those things where you only get one chance to get everything in place and the resins and glass consolidated before things are locked together permanently. The forgiveness is that there are ways to repair the laminate with additional time and money. There will be grinding and dust and reworking something that could have been done better from the first time. online pharmacy viagra paypal Repairing will not look as nice, nor perform as well as a properly planned and completed first attempt. Safety is something that needs lots of attention. The processes are very operator dependent and we are working with chemicals here, so workers must be protected. Many of these chemicals are regulated by several government agencies. This is why these chemicals are generally difficult to obtain on the street. The styrene-based polyesters and vinylesters require respiratory protection and skin protection, as styrene is considered by some (California) to be a possible carcinogen. There is a time weighted average for breathing...

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