Hot And Humid Environment, The Hybrid Composite Interlaminar Fracture Toughness,

In present thesis, the mixed-mode interlarninar fracture characters of composite laminate T300/5405 on hygrothermal conditions were investigated using new mixed- mode flexure (MMF) specimens. It has been found that at room temperature, moisture absorption had little effect on the mixed-mode interlaminar fracture toughness of T300/5405, but at high temperature, the fracture toughness of laminate increased as the moisture content increase. No significant influence of temperature on fracture toughness was observed when the volume of moisture content was low; but when the specimen has absorbed much water, its fracture toughness increased as temperature increase when the temperature was above 600C. The tough fractographs could be seen in socked specimens and high temperature specimens. It has also been found that mixed-mode delamination failure criteria were straight lines expressed by G1~,, and 0itm? the mode I and mode II components of mixed-mode interlaminar fracture toughness. The MMF specimen has been simulated using 8-noded elements. The FEM results showed that MMF method provided correct Gum values, but there was some difference between the Gum values from FEM and from beam theory. The 0im values from FEM were less than those by about 30 percent. The differences may come from the assumption in beam theory. A modification was made to the equation of Gum according to the FEM results. It is very useful for the MMF testing method.