Mechanical strength of carbon fiber tube
Carbon fiber composite materials have unique and superior properties such as light weight, good stiffness, high specific strength, high specific modulus, high temperature resistance, good fatigue resistance, and designability. Components or structures made of this material have only traditional weight. 80% of the material. In recent years, due to the many applications of wound CFRP pipes in aerospace, offshore platforms, underwater structures, pressure vessels and other fields, the design and mechanical properties of filament wound CFRP pipes and pressure vessels have become composite materials at home and abroad. hotspot in structural research.
We studied the strength characteristics of CFRP pipes through experiments, which laid a good foundation for the further application of CFRP pipes in civil engineering. Preparation of test specimens The materials used for the test specimens are T700SC carbon fiber (Toray Company, Japan) and epoxy resin. The fibers are laid longitudinally and circumferentially. The longitudinal fibers mainly provide tensile and compressive resistance; Strong and resistant to accidental transverse shear, the layup method is (0°, 90°) s.
By observing the stress-strain curve obtained by the compression experiment of CFRP pipe, it is found that the CFP pipe made of this material has excellent compressive strength, the average strength is 230MPa, and the strain reaches 5.2×10^-3. In the experiment, there was almost no visible change before loading to 80% of the failure load, and when it reached 80% of the failure load, a crackling sound was heard, at which time the resin began to crack. The failure occurred suddenly, and a violent breaking sound could be heard, which belonged to brittle failure. By observing the cross-section, the resin was cracked, and it was found that the hoop fibers were broken and the longitudinal fibers were broken. This shows that when the CRP pipe is compressed, the load is mainly borne by the matrix, and its strength depends on the strength of the matrix.
Observe the stress-strain curve obtained from the tensile test of the CFRP tube. Compared with the stress-strain curve of the compression experiment, there is a big difference. By analyzing the strain data, it can be seen that when the deformation strain of the specimen reaches 0.005, a crackling sound is emitted, and the resin begins to have fine cracks, but cannot be observed with the naked eye; when the strain reaches about 0.015, the resin has a large range on the tensile section. Cracking, the fractured resin quits work, and the load is mainly borne by the fiber; the load continues to increase, but the deformation of the specimen increases faster, and the stiffness degradation is very obvious; until the fiber is broken, the specimen is damaged. When broken, the tensile strength of the CFRP pipe is over 800MPa, and the strain is as large as 0.03, which shows that the CFRP pipe has good tensile properties.
Compared with steel, CFRP pipe has the characteristics of light weight and high strength. In particular, the tensile strength is over 800MPa. However, CFRP materials are brittle materials, and the compression failure shows obvious brittle fracture characteristics. When the strain of CFRP pipe is within about 0.015, the stress-strain curve changes linearly. With the visible cracking of the resin, the stiffness of the pipe is seriously degraded, and the deformation increases sharply.