【作者】 李本禄；

【导师】 孙东立；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2010， 硕士

【摘要】 连续碳纤维增强铝基复合材料(Cf/Al)具有高的比强度、比刚度等优异特性,在航空航天领域具有巨大的应用潜力。长纤维增强的机翼,机身,尾板等,均要求具有高压缩强度,然而相关研究却十分少见。复合材料中不同类型缺陷对性能的影响不尽相同,研究缺陷对性能的影响规律迫在眉睫。本试验在复合材料中人工制备了类型、尺寸确定的夹杂、分层、铝层缺陷,并通过电火花打孔来模拟结构孔洞。其中夹杂、分层和铝层缺陷的长度分别为2、4、6和8mm,厚度0.2mm,宽10mm;孔洞缺陷均为通孔,直径分别为0.3、0.45、0.55、0.8、1.4和1.8mm。研究缺陷厚度的影响时,铝层缺陷厚度分别为0.05、0.08、0.1和0.15mm,缺陷长4mm,宽10mm。缺陷经超声检测确认尺寸与位置。单向C_f/Al复合材料的纤维方向压缩强度为1337MPa,压缩模量245GPa,垂直于纤维方向的压缩强度为185MPa,压缩模量25GPa;0°/90°层合复合材料的压缩强度为584MPa,压缩模量为120GPa。±45°层合复合材料的压缩强度为200MPa,压缩模量70GPa。无缺陷复合材料的纵向压缩破坏主要由复合材料在压缩应力下的鼓起变形导致,纤维鼓出发生屈曲,进而扭折断裂引起复合材料的失效破坏;横向破坏取决于纤维/基体界面的开裂和铝基体屈服。0°/90°层合复合材料的压缩破坏取决于纵向纤维的失效破坏,不同铺层间发生层间开裂;±45°层合复合材料在压缩应力下出现层间剪切,一部分纤维沿界面发生剥离,整体滑移,另一部分纤维沿径向剪切断裂。缺陷对复合材料压缩断裂的影响主要在于纤维绕过缺陷时在边缘发生倾斜变形,在压缩应力下易于发生剪切扭折断裂,进而造成复合材料的整体破坏。层状缺陷的长度逐渐增大,复合材料的压缩强度先降后升,在单向复合材料中的降幅大于层合复合材料。拐点的位置由纤维倾斜变形和界面开裂共同决定。单向纤维增强复合材料的压缩强度对孔洞敏感,但孔洞直径的改变对压缩强度的影响较小。层合复合材料对孔洞缺陷不敏感,压缩强度随孔洞直径的增大线性下降。缺陷的厚度变化,压缩强度也随之发生改变,当厚度较小时,随着厚度的增加压缩强度线性下降。更多还原

【Abstract】 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.更多还原