On the evaluation of impact damage on composite materials by comparing different NDI techniques

The dynamic behavior of composite laminates is very complex as there are many concurrent phenomena during composite laminate failure under impact load. Fiber breakage, delaminations, matrix cracking, plastic deformations due to contact and large displacements are some effects which should be considered when a structure made from composite material is impacted by a foreign object. Thus, an investigation of the low velocity impact on laminated composite plate of epoxy resin reinforced by carbon fiber is presented. The influence of stacking sequence and impact energy is investigated. The impact testing is conducted with a vertical drop-weight testing machine. Non destructive testing is performed and the amount of damage is quantified in terms of area. The performances of ultrasonic testing, optical thermography and sonic infrared for the inspection of composite laminates with barely visible impact damage are evaluated. Finally, a comparison amongst their capabilities for such application is carried out.