Muhammad-Umar Saeed

Comparison of Fracture Characteristics of Open-Hole-Notch Carbon-Fiber-Reinforced Composites Subjected to Tensile and Compressive Loadings

Open-hole tension (OHT) and open-hole compression (OHC) tests were carried out on hot-pressed carbon-fiberreinforced composite samples with a singular open hole. The fracture surfaces of the OHT- and OHC-tested specimens were examined by using scanning electron microscopy (SEM). SEM micrographs showed significant features on the surface of carbon fiber, matrix, and especially in the fiber/matrix interface. Interpretation of these micrographs revealed the possible failure mechanism of composite samples with an open hole under tensile and compressive loadings. Furthermore, a comparative study of these micrographs also pointed to certain specific differences between the fracture characteristics of open-hole composite samples failed under tension and compression. This information is useful in the post-failure analysis of a composite structure.

Fabrication of Microchanneled Composites by Novel Selective Polymer Degradation

In this research a new low-cost, highly compatible method is proposed and demonstrated to create microchannels within carbon fiber reinforced polymeric (CFRP) composite laminates that caused a lower mechanical loss due to their presence. In it, microchannels were created within the CFRP composite laminate by selective degradation of the specially selected polymer, whose solid preforms were placed at specific locations within dry fabric layers during composite manufacturing by resin infusion. Interlaminar shear (ILSS) and three-point-bend flexural tests were carried out on CFRP composite laminates with and without microchannels of different diameters to assess their effect on structural strength. The results showed that inclusion of microchannels within the CFRP composite laminates decreased their ILSS and flexural strength, which decreased steadily with the increase in channel diameter. The mechanism for these observed results was found to be the creation of resin-rich areas, microchannels and lessened fiber content by the addition of microchannels. These mechanical testing results were compared with the results of CFRP composite laminates with microchannels, inserted by hollow glass tubes (HGTs), and it was found that the new applied strategy was quite effective in introducing microchannels within CFRP composite laminates with reduced mechanical loss and provided more space for additional functionalities.