Study On Low Energy Impact Damage Of Carben Fiber Reinforced Plastic Laminated Composite

In last decades, a significant progress, especially in aviation field, has been madein composite designing and manufacturing. The composites have been used not onlyas the non-primary load-bearing member but also the main bearing components. Theusing of integral and complex structure composite is increasing, and become a trendto design-manufacture integrated mode. The carbon fiber reinforced plastic composite(CFRP) has excellent performance except the sensitiveness to the impacts, which willlead to the damages on surface and inside of composite. Those visual or potentialdamages, which focused by researchers’ home and abroad, have bad influence to theperformance even they are too small to detect.In this paper, the porosity of CFRP laminated boards, with different structure,was observed by ultrasonic A-scanning method, and then the samples were separatedinto different group base on that result. After that, the impact experiments in gradientway to increasing energy were carried out, and the damage on surface and inside ofcomposite has been detected by super depth there-dimensional microscope andultrasonic C-scanning equipment respectively. Additional, impact damage of impactedboards with different porosity was studied, and the gas-tightness of that was tested.The results show that the porosity of A-type composite can be divided into threegroups with porosity,0.08%,0.096%and0.112%, and0.078%,0.09%and0.104%for B-type. There is a pit formed in the surface of board after impacting once theenergy over11J. Many cracks around pit will appear, and the sizes of pit and crackswill bigger if the energy increased via super depth there-dimensional microscope. Thefiber and resin fracture, delamination and other damage phenomena inside thesamples was detected by ultrasonic C-scan. By analyzing the pit depth and the airtightof board, porosity was found has relationship to damages.Viscoelastic is significant feature of CFRP composite exist in impacting. Therelationship between porosity, impact energy and pit rebound behavior were studiedrespectively, and energy consumption caused by viscoelastic response of laminatedplates was calculated in this work. The results showed that: the rebound phenomenonof impact pit is obviously. The pit depth decreases, which affect by porosity andimpact energy, as time goes in168h. The rebound ratio of pit is45.5%,44.2%, and43.9%respectively for A-type CFRP laminates with porosity0.08%,0.096%and0.112%impacted by11J, and32.4%,32.2%, and31.8%for B-type CFRP laminateswith porosity of0.076%,0.09%and0.104%respectively subjected to31J impactenergy. The pit depths of two types laminates rebounded impacted by all differentenergy and in the same trends basically, but with different velocity. For both laminates,the porosity has very little effect to the rebound velocity and energy consumer ratio contrary to impact energy. The rebound velocity was increased but energy consumeratio decreased with impact energy increasing obviously.