Semi-rigid urethane based fiber composite shafts are fabricated by high pressure injection molding process. The samples are made in Georgia Southern University’s laboratory where compressed air pressure is effectively used for this purpose. A special manufacturing process is suggested which can be used for mass production of these composites. This unique manufacturing technique creates a composite shaft with a core made of matrix material which is completely wrapped around by a woven fiber cloth with a very strong bonding between core and fibers. Three different types of woven fibers: fiber glass, Kevlar 49, and carbon fibers, are used. Triple point bending tests are carried out to test these three different types of composite samples and also samples made of only base or core material. During the test as the applied load is increased, a linear trend is observed between the load and mid-point deflection of the specimens up to a certain level. Higher load causes separation of fibers and core matrix and followed by local buckling of the separated fibers that are under compression region. This phenomenon brings down the bending stiffness of the composite significantly and it is quite pronounced in the load deflection curve diagram. Failure modes are observed to differ for each of these three types of composite and are discussed in details here. Composites with fiber glass wrapping are found to be the strongest among the three. Future work will involve determining the torsional and fatigue properties, and also the effect of fiber orientations on the mechanical properties of these composites.
It has been already established by different investigators that addition of nano-reinforcements to plastics and fibers further enhances the mechanical and thermal properties of these materials. In this investigation, we have tested a bi-layer composite armor made of a ceramic layer and a nano-reinforcement infused epoxy layer. Our objective is to determine whether the infusion of nano-reinforcements in an epoxy layer enhances the ballistic properties of this bi-layer armor system. This bi-layered armor which was made of an alumina layer and a nano-infused epoxy layer was tested by a Fragment Simulating Projectile (FSP) method. Silica nanoparticles and multi walled carbon nanotubes (MWCNT) with a loading range of 0–1wt% were used for this purpose. Armors having the same thickness but made of only a single pure ceramic layer and a bi-layer composite made of a ceramic layer and a neat epoxy layer were also tested for comparison purposes. A gas gun with high velocity projectile was used to perform the experiment. A striking velocity of about 400m/s was used to hit the target armor plate. The striking velocity of the projectile was obtained by maintaining a breach end pressure of helium gas in the gas gun at about 500 psi. The striking velocity was chosen at a level which was well above the ballistic limits of the armor materials. A finite element analysis was also performed to evaluate the ballistic properties of the composite armor and to compare those with the experimental data. Numerical and experimental results for the residual velocity of the piercing bullets were found to be in good agreement. Details of the experimental and numerical data are presented in this paper.
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