The defects in carbon fiber composites are mainly from two aspects: one is the defects of the raw materials and the other is the manufacturing defect. The common defects are porosity, inclusion, crack, porosity, fiber layering and fracture, fiber and matrix interface cracking, fiber crimp, rich or poor gum, fiber volume percentage is very poor, fiber / matrix interface is not good. Here are two most common defects in the stratification and pore.

Delamination refers to the dehiscence or dehiscence between layers, which is a typical defect in the structure of carbon fiber composites. The hierarchical formation are as follows: the matrix fiber between the thermal expansion coefficient mismatch or stored for a long time without treatment; reinforced materials; resin content is too low; the adhesive curing process improper or unreasonable, pressure control is not accurate; the adjacent layer layer between the interval of time; early curing resin. The delamination between fiber layering is the most serious defect type in carbon fiber reinforced polymer composites, which influences the integrity of structures by reducing the compressive strength and stiffness of materials. Under the conditions of mechanical or thermal load, the stratification in the structure will be transmitted, and the material may be broken when the condition is serious.

Pore is a hole formed in the process of composite forming, and it is one of the main defects of carbon fiber composites. The extension is generally divided into: single pore (including fiber bundle pore and pore plate). When the porosity is less than 1.5%, the pore is spherical; when the porosity is more than 1.5%, it is generally columnar shape, and the pore is parallel to the fiber axis. Porosity in CFRP mainly affects interlaminar shear strength, longitudinal and transverse flexural strength and modulus, longitudinal and transverse tensile strength and modulus, compressive strength and modulus. Studies have shown that porosity increases from 1% to 0~5%, the interlaminar shear strength decreases by 7%, the bending modulus decreases by 5%, and other properties decrease by about 10%.

To produce high quality carbon fiber products, every step in production must be strictly controlled to avoid defects.

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