Study On Compressive Failure Behavior Of C_f /al Composites With Artificial Defects

Continuous carbon fiber reinforced aluminum matrix composite (Cf/Al) has high properties such as high strength and stiffness. Although the axial compressive strength is most important for long-fiber-reinforced wings and fuselage, the research on compression strength is very rare. Different defects have different influence on compressivon properties, and the influence need to be researched.Artificial defects were preset in composite, and holes were made by electrical spark perforation. The inclusion, aluminum congcentration and delamination defects were prepared with certain size. The length of these desrects varies, from 2mm to 8mm, 2mm each step. The holes were prepared by electrical sparkerosion perforation. The diameter contained 0.3, 0.45, 0.55, 0.8, 1.4 and 1.8mm. When the thickness changed, the length is 4mm, and thickness 0.05, 0.08, 0.1, 0.15mm.The longitudinal compressive strength of unidirectional Cf/Al composite is 1337MPa, compression modulus of 245GPa. The transversal compressive strength of unidirectional C_f/Al composite is 182MPa, compression modulus of 25GPa. The 0°/90°laminated composite compressive strength is 584MPa, compression modulus is 120GPa. The±45°laminated composite compressive strength is 200MPa, compression modulus is 70GPa.The failure of longitudinal composite with no defects was due to the fibre buckling under compress. The fibre fracted led to the composite failure. For transversal composite, the reason of failure was interface cracking and matix yielding. The 0°/90°composite fracture was similar to the longitudinal composite. The plies detach when fracted. The±45°composite showed interlaminar shearing under compressive. The influence of defects was declining the fibre, so the fibre was easy to fract by shearing.The existence of lamellar defects made the compression strength of composite first down then up. The level of the unidirectional composites was larger than laminated composite. The location of the turning point was decided by the slope of the fibre and interface cracking. Unidirectional fiber reinforced composite materials was sensitive to the hole, but the diameter changing had little effect on the compressive strength. Laminated composite was not sensitive to the hole defect.The strength decreased linearly with the pore diameter increasing. The thickness of defects changing, the compressive strength also changed, when the thickness is small, with the increase of the thickness of the compression strength decreases linearly.