Experimental and numerical study of the effects of fiber orientation on stress concentration of CFRE

Carbon fiber reinforced composites are broadly employed, as structural members, in many industrial applications especially in the avionic industry due to their high strength-to-weight ratio. Circular holes are commonly used in these members for fastening, bearing, reducing weight, and others. Therefore, several experimental and analytical studies were introduced to figure out the stress concentration behavior around the vicinity of the holes under different loading conditions. However, no reports are delivered to study the effect of fiber orientation on the stress concentration factor of unidirectional carbon fiber reinforced epoxy (CFRE) composites with a hole under tension. Thus, the current work is targeted to understand the relationship between stress concentration factor (SCF) and fiber orientation in CFRE orthotropic plates. The unnotched and notched composite samples, with four different fiber orientations, were experimentally investigated in a tension test. The SCF of samples was calculated using analytical and computational FE methods. The failure criterion of open-hole tensile (OHT) test samples was also analyzed. The experimental results demonstrated that there is no significant effect of fiber orientation on the normalized strength. Yet based on the stiffness matrix of isotropic materials, a pronounced effect of the fiber orientation on the SCF is detected when using analytical calculations. The present research arises the need for further investigations to find a correlation between experimental and analytical results of SCF in unidirectional CFRE with a central hole at different fiber orientations.