Identify the defects in the graphiteepoxy composite laminate

Identify the defects in the graphite/epoxy composite laminate to the right, how they are formed and why they are detrimental to a composite strength.

Solution

The defect in the picture shown is porosity defect. Such defects are common in graphite epoxy composites. They are formed due to air entrapments in the matrix. Porosity is caused by incorrect cure parameters like duration, temperature, pressure, or vacuum bleeding of resin. Presence of air entrapments effect the mechanical properties such as inter-laminar shear stress of the composites. Hence these are detrimental to the composite strength.