Influences of various thermoplastic veil interleaves upon carbon fiber-reinforced composites subjected to low-velocity impact

Throughout their service life, composite materials may be subjected to impact loads, which can result in some damage mechanisms that cause degradation in mechanical and dynamic responses. Especially matrix-induced cracks and delamination can have significant effects on the final properties, and cause serious problems if the necessary precautions are not taken. In the current study, Carbon Fiber-Reinforced Polymer (CFRP) composites interleaved with Fine Glass (FG), Polyetherimide (PEI), Polyetheretherketone (PEEK), Polyimide (PI) and Poly-Phenylene Sulphide (PPS) thermoplastic veils were fabricated, and exposed to LVI tests under 25.2 J constant impact energy to determine how veils affect the dynamic properties. The selected veils are commercially available materials and are used for various purposes. In this regard, it was aimed to examine the usability of these commercially available veils as interlayers and to examine the impacts of the veils used as interlayers on the LVI characteristic of CFRP composites. According to the present study, it was found that veil interleaves significantly affect the composite stiffness, and accordingly, relevant LVI responses such as total impulse, bending stiffness, interaction times etc. For instance, approximately 21.2% reduction in the peak displacement and 73.23% increment in the bending stiffness were observed due to FG veil interleaves. On the other hand, when the effects of veil types were examined, the maximum and minimum variations in the LVI responses were observed for the FG and PEI interleaves, respectively, and FG veils were found to be the most effective veil types for the CFRP composites. It was also revealed that veil interleaves strengthen the interlaminar region between plies and delamination resistance, and thereby improved the Delamination Threshold Loads for all configurations.