Compounds and Composites
Composites are materials reinforced with another material to enhance its properties. Compression molding is the process which the materials are manufactured. Our materials are thermosets, which cannot be reheated to change its shape. However, it has the advantages of having a higher modulus, strength, durability and chemical resistance because of its resin.
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The material for our experiment is Glass Fiber Composite (GFC), which comes in Bulk Molding Compound (BMC), Sheet Molding Compound (SMC), discontinuous woven glass fiber composite (MAT), and strips of the glass fiber weave (TRIM). These composites are either homogeneous or made with a combination of materials.
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A composite made of SMC between of foursheets of woven glass fibers.
A composite made of BMC between of foursheets of woven glass fibers.
A composite plastic made of 1"x0.5" Trim sandwiched in between 4 layers of recycled woven glass fibers. (two on top and bottom).
A composite made of SMC between of foursheets of woven glass fibers.
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Bulk Molding Compound is randomly oriented glass fibers mixed with epoxy. This provides the material with extra stiffness and strength with just epoxy alone. By contrast, sheet molding compound consists of flat sheets of randomly oriented glass fibers which are stacked and compressed when molded. In comparison, woven glass fiber composite discontinuous woven fabric of glass fibers pre-impregnated with epoxy resis (prepreg epoxy). The most costly of these material is the woven composite, which the group strives to recycle the unused leftover material.
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the The materials were cut using a Fanuc Robodrill, into different shapes for the three testing methods with a tolerance of +-.005. The most extensive method, three point bending, was cut into 12" x 12" x .5" squares. We labeled each material and recorded its proper dimensions which were used in the calculations of the analysis of the materials.
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Including homogeneous materials (with BMC, SMC, Trim and Mat), combinations were also manufactured for the tests. By sandwiching the material, a stiffer material can be used while minimizing more expensive components. These sandwiches include, two outer layers of Mat with BMC or SMC in the middle layer, an outer layer of SMC with a BMC core, a combination of Mat and BMC, and BMC with a combination of Mat and SMC.
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The purpose of this organization is based on the sandwich theory, which describes a combination of a plates and beams to create a more rigid material. A sandwich structure consists of a moderately stiff inner layer with a stiff outer layer. The outer layers product a higher bending stiffness because of this combination while maintaining a low weight. In the case of our experiment, it keeps the cost lower while minimizing stiffer and more expensive material. This combination of material will be applied at the core of the manhole cover to provide better stiffness than Mar-Bal's original combination.