Fatigue behavior of notched CPLY composite laminates

This paper describes the Tension-Tension Fatigue behavior of notched CPLY composite laminates. NCF Carbon fiber of 20 bilayer plies were stacked to fabricate [0/-45/90/45]10 quasiisotropic laminate, and metal pins were inserted into the dry fabric at specific distances without causing any damage to the carbon fiber strands. They were infused with epoxy resin using HVARTM (Heated Vacuum Assisted Resin Transfer Molding). The laminates were cured as per the manufacturer's specifications using the out-of-autoclave oven curing method, and after curing metal, pins were popped out from the laminate. This resulted in holes in the panels without any damage to the continuous carbon fiber strands. The fabricated laminates were then cut into test coupons using a water jet to obtain holes precisely at the center of the coupon. From the remaining panel, coupons were machined and drilled using traditional drilling and non-traditional water jet machining process to get the notch exactly at the center. Axio Image upright microscope was used to study the fiber breakage on the edges of drilled, water jet cut, and a pin inserted hole. Static tests were performed as per ASTM D3039 to evaluate tensile strength and stiffness. The coupons were then tested using the ASTM D3479-19 method to study the Tension-Tension Fatigue behavior of the notched CPLY the laminates. The fatigue testing involved testing three coupons at each load level, starting from 70% of the ultimate tensile strength (UTS) to 50% of UTS insteps of 10%. All the fatigue tests were conducted under the load-controlled tension-tension with a stress ratio of R=0.1 and at 3 Hz frequency with constant amplitude.