Research On The Impact Damage Of Carbon Fiber Reinforced Epoxy Composite With Copper Mesh Protection Layer

Carbon fiber reinforced epoxy composite with copper mesh protection layer have excellent mechanical properties, heat resistance, corrosion resistance, fatigue resistance, and which is a good performance in lightning proof, are widely used in aircraft manufacturing and other fields. The laminated composite structures are more sensitive to impact, under the low- velocity, the inner structure may appear matrix cracking, delamination and fiber breakage etc, but copper influences the impact performance.The impact damage of carbon fiber reinforced epoxy composite with copper mesh protection layer was researched in this paper, and its result would be good to design and use of composites.In this paper, plain weave carbon fiber and epoxy were used as the reinforced and base material, copper mesh as a surface protection layer,to prepare composite materials of 8, 9 and 10 layers of carbon fiber and 10 layers of carbon fiber with free copper mesh by hand lay-up molding method. All these four groups of specimens were impacted by six kinds of the impact energy of 1.4 J, 3 J, 5 J, 7 J, 9 J, 15 J by a pre-impact damage testing machine. Composite materials with different impact energy were detected by immersion ultrasonic C-scan and phased array ultrasonic testing. Appearance of the damage, impact force, indentation depth, impact energy, delamination area were analyzed to study the influence of the impact performance, and the relationship of composite delamination damage and the invisible damage. For the impact delamination with copper mesh protection layer composite proposed a new delamination model.The results of this paper are as follows:1) As can be seen from the appearance of the damage and detection of ultrasound s-can, under the same impact energy, the delamination area of the composite with copper mesh protection layer were around 59% smaller than the free copper mesh. Impact performance significantly was better than free copper mesh;To a certain degree, with the increasing of carbon fiber volume, the impact performance of the composite was improved. The delamination areas of 10 layers of carbon fiber laminates were around 28% smaller than 9 layers, and 50% smaller than 8 layers. Under the same impact energy, the bigger of fiber volume content, the higher of the strength, the less of damage areas.2) Under the same impact energy, the impact force of the composite are around 19.7% smaller than the free copper mesh, the dissipated energy are around 20% smaller than the free copper mesh. This is due to storage and absorb some of the impact energy of copper mesh protection layer as well as its load spreading effect during the impacting, which is reason that damage resistance increased under the impact.3) The copper mesh protection layer had a mechanical protection, under the same impact energy, indentation depth of the composite were around 45% smaller than the free copper mesh, significantly improved damage resistance under the impact.4) Under the different impact energies, there were two damage mode of composite delamination damage, Assume an impact energy threshold when the impact energy is less than the value, delamination occurred at the bottom portion of the laminate in the thickness direction, and only slightly. When the impact energy is greater than the value, the delamination is on superposed with conic shape delaminations, have a great influence on the structure and properties of the composite. Threshold value of 8 layers, 9 layers,10 layers of carbon fiber laminates was equal to 2 J, 4 J, 6 J.And corresponding to the depth of the indentation depth was 0.24 mm, 0.17 mm, 0.22 mm. They were less than visually visible damage threshold 0.3 mm.