Experiment 8: Composite Materials

Composites consist of two or more phases that are usually processed separately and then bonded, resulting in properties that are different from those of either of the component materials.

Polymer matrix composites generally combine high-strength, high-stiffness fibers (graphite, kevlar, etc.) with low-density matrix materials (epoxy, polyvinyl, etc.) to produce strong & stiff materials that are lightweight.

Laminates are generally built up from multiple layers of lamina; the fibers within each lamina are generally parallel, but laminates usually contain lamina with their fibers oriented in various directions. Each lamina is an anisotropic layer with properties varying as a function of fiber angle.

Loading along the fibers (longitudinal) is modeled as Isostrain while loading perpendicular to the fibers (transverse) is modeled as Isostress; these two directions generally represent the extremes in material behavior.

Fiber and matrix material property data can be used to predict/approximate the properties of laminated composites using the Rule of Mixtures.

In this investigation, the elastic modulus of composites loaded at various angles with respect to the fiber direction will be predicted, tested and discussed. The burn-off method will be applied to determine the fiber volume of the composites being investigated; and ultimate strength and elastic modulus results will be compared with those of metals and polymers.

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