Fiber-reinforced composites with embedded fibers

Predicting fiber orientation. Isotropic constitutive models are not valid for injection-molded fiber-reinforced composites. Unless the embedded fibers are randomly oriented, they introduce anisotropy in the thermomechanical properties of the material. The fiber orientation distribution is induced by kinematics of the flow during filling and, to a lesser extent, packing. An extensive literature deals with flow-induced fiber orientation while much other work has been devoted to micromechanical models which estimate anisotropic elastic and thermal properties of the fiber-matrix system from the properties of the constituent fiber and matrix materials based on given microstructures. Comprehensive reviews of both research areas have been given in two recent books edited, respectively, by Advani and by Papathanasiou and Guell where many references can be foimd. 

Micromechanical models such as Cox shear-lag and Halpin-Tsai are often used to predict the stiffness and strength of discontinuously short-fiber reinforced composites. Experimental results of tensile measurements are then compared or correlated with such theoretical models. The shear-lag analysis originally proposed by Cox considered a discontinuous fiber embedded in an elastic matrix with a perfectly bonded interface and loaded in tension along the fiber direction [25]. The analysis tabes into account the difference in strain displacements of the fiber and matrix along the interface. The stress transfer depends on the interfacial shear stress between the fiber and the matrix. The stress transfer from fiber ends is neglected in the analysis. The Cox model incorporates the aspect ratio (a = l/d where I is the fiber length and d the diameter) of the fiber into... 

Zhao, X., et al. Strain monitoring in glass fiber reinforced composites embedded with carbon... 

Kunz and Kirschning developed a chemically functionalized monolithic material which is based on a glass/polymer composite [28,29] (refer to Sect. 3.1). This material is available in different shapes including rods, disks, and Raschig rings. The polymeric phase of this composite was chemically functionalized (e.g., substitution of the benzylic chlorine by trimethylamine or sulfonation). Rod-shaped objects were first embedded in a solvent-resistant and shrinkable PTFE tube. This was followed by encapsulation with a pressure-resistant fiber-reinforced epoxy resin housing with two standard HPLC fittings, which created... 

Metal matrix composites (MMC) consisting of fibers embedded in a metal ceramic matrix. Fiber-reinforced plastics (FRP) made of a polymer matrix reinforced with fibers. 

When the polymeric component forms the continuous phase, spheres, cylinders, or platelets may be added, as illustrated under reinforced polymers. The fiber composites are the most highly researched, as far as different modes of mixing are considered. The filaments may be continuous or discontinuous, or oriented or random in the matrix, with many subclasses of partial orientation possible (not shown). The tape composites are interesting since in some quarters these may be considered a two-dimensional analog of the highly oriented, continuous fibers embedded in a plastic matrix. The reinforced elastomers differ from the reinforced plastics in two ways the mechanical properties of the polymeric substrate, and the size of the reinforcing particles with respect to polymer chain dimensions. Because of the poor properties often obtained, it is rare to see a research paper on large particles dispersed in an elastomer. 

Hierarchy can be described in analogy to rope (stretched polymer molecules in domains that make up nanofibers, combined to microwhiskers, bundled into fibers that are spun into yarn that is twined to make up the rope). Wood and tendon are biological examples that have six or more hierarchical levels. Compared to these, fiber-reinforced matrix composites made up of simple massive fibers embedded in a metallic, ceramic, or polymer matrix are primitive. Hierarchical inorganic materials, as discussed in Chapter 7, can be made with processes for fractal-like solid products spinodal decomposition, diffusion-limited growth, particle precipitation from the vapor, and percolation. Fractal-like solids have holes and clusters of all sizes and are therefore hierarchical if the interactions... 

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