Composite sandwich panels subjected to quasi-static load and low velocity impact

Much research and destructive testing have been done on composite sandwich panels either by quasi-static loading or by low velocity impact. However, there are few which have touched on CFRP composites and both types of tests at the same time. This investigation aims to study the structural response of CFRP Composite Honeycomb Core Sandwich Panels subjected to Quasi-Static Load and Low Velocity Impact. The composite sandwich panels were all fabricated in house using prepreg layups and cured using the hot vacuum table. The specimens were 100mm x 100mm x 28mm samples consisting of 2 CFRP laminate facesheets and a Nomex honeycomb core, bonded together by adhesive. The facesheet layup orientation to be tested is [0/90]8 but a variation of [-45/45, 0/90]2S is also tested. For the Quasi-Static Tests, they were performed on the Instron 5500R machine. Quasi-Static Tests were conducted at crosshead compression rate of 0.5mm/min till sandwich panel failure. For the Low Velocity Impact tests, they were performed on the Dynatup 8250 impact testing machine with varied impact energies for no failure, partial failure and complete failure of the sandwich panel. The experimental results showed that the geometric thickness of a honeycomb core does not affect the outcome of maximum load achieved, energy absorbed and stiffness of the sandwich panel either for an impacting or quasi-static tup. Also, the crosshead velocity does not affect the maximum load nor the stiffness value of the sandwich panel. The geometric core cell size affects the maximum load of the sandwich panel. Energy at Impact affects the Maximum Tup Displacement of which the impactor tup will deflect into the sandwich panel. Quasi-Static Tests showed that there is a slight decrease in the Maximum Load while an increase in sandwich panel stiffness. The graphs of Load vs Tup Displacement of Quasi-Static Tests, Load vs Tub Displacement and Load and Tup Displacement vs Time of Low Velocity Impact Tests were studied in detail. The common characteristics, trends and anomalies were identified. It was discovered that the Diameter (Ø) of Damage, created by the tups in all experiments, were arbitrary and that there is no relationship between the diameters and an experimental parameter outcome or material property. The Flexural Rigidity, D, and the Young’s Modulus (Ultimate), EU, of a monolithic facesheet laminate could be determined from the solution derived from Plate Theory, a relationship between D and the maximum deflection of a centrally loaded clamped circular plate. With D determined by experiments, the solution can be used to predict the maximum defection.Bachelor of Engineering (Aerospace Engineering