A study has been made to establish an optimum condition in the surface treatment and curing process. These will be an important parameters for the fabrication of multilayered hybrid composite material, Al 7075 / CFRP CARALL(CARALL: carbon fiber reinforced aluminum laminates). Considering of the abov...
A study has been made to establish an optimum condition in the surface treatment and curing process. These will be an important parameters for the fabrication of multilayered hybrid composite material, Al 7075 / CFRP CARALL(CARALL: carbon fiber reinforced aluminum laminates). Considering of the above results, 2, 4, 6 and 8 ply CARALL were fabricated with 0.25mm thickness Al 7075-T6 alclad sheet (KAISER Co.), FM 300M adhesive film (CYTEC Co.) and 0.13mm thickness F584-4 carbon epoxy prepreg (HEXEL Co.) in autoclave. Effects of carbon fiber direction and thickness variation in tensile strength were investigated by experiment and theoretical approach. Damage behavior of carbon fiber laminates and CARALL laminates were investigated also. Moreover, in order to study the characteristic of strength decrease by drilling on manufacturing and assembling of aircraft parts, specimen were made with circular hole notch and tested on tensile strength experiment. Characteristic of notch tensile strength and modified failure prediction criterion were reviewed in this experiment. The results are as follows : 1. The PAA (phosphoric acid anodizing process) provided the best adhesive strength among the specimens. On the other hand, the poor adhesive strength was shown on the vapor degreased and CAA (chromic acid anodizing process) and FPL (sulfuric . sodium dichromate acid etching process) was nearly same to the PAA. 2. The adhesive strength of the co-cured Al and carbon fiber prepreg higher than that of secondary cured one. But with respect to the dimensional stability, the secondary curing method was better than co-curing method. In secondary curing method, the condition of 0.35 MPa pressure shown higher adhesive strength than 0.6 MPa pressure condition and it was shown that the increaser curing time, the increaser adhesive strength. The effectiveness of adhesive strength increasing according to curing time was effective in 90 min curing time rather than 120 min curing time. 3. DMA(Dynamic Mechanical Analysis) test revealed T_(g) in curing times over 60 min is nearly same, so it is estimated they will have similar degree of curing and joint durability in using FM300M adhesive film. Considering of the results of the above mention, the condition of 0.35 MPa, 90 min, secondary curing method with PAA treated Al is recommended to fabricate the precise, high adhesive and durable aircraft parts. 4. High strength CARALL hybrid composite was fabricated with thin Al 7075-T6 sheet and adhesive film instead of glass fiber. The effect of strength enhancement was shown in case of using more than 4 ply F584-4 carbon prepreg. 5. As the results of analyzing the state of stress distribution of section of CARALL, by the FEM analysis of CARALL of L(0°) direction, 4 ply, it was found that a partial stress increase in order of epoxy adhesive, Al 7075, CFRP. And the partial stress of CFRP carried out a great portion of applied stress. 6. The real failure strengths of L(0°) direction, 4 ply CARALL were a little lower than theoretical strength by the law of mixture, but in case of 6 and 8 ply CARALL , the strengths were nearly equal to theoretical strength. And in case of 45°and T(90°) direction, the strengths of 2, 4, 6 and 8 ply CARALL were nearly equal to theoretical strength also. So it is estimated CARALL nearly satisfy the law of mixture in spite of fiber direction and thickness. 7. The impact resistance of CARALL was higher than that of CFRP. This is because both side Al sheet of CARALL absorb a great of impact damage. 8. Notch sensitivity of CFRP was decreased by hybriding with the high strength and high notch sensitivity CFRP material and ductile Al 7075. 9. Characteristic length d_(0) was different in Al 7075, CFRP, CARALL and vary with hole diameter 2R and width W. Notch sensitivity coefficient k increase in order of Al 7075, CARALL, CFRP. In same material, coefficient k decrease with increasing width. 10. Kims' modified failure prediction criterion was satisfied in CARALL, CFRP, Al 7075 better than Whitney's criterion. Between characteristic length d_(0) and notch strength, there is in inverse proportion, d□ increase with width W in same notch strength.
A study has been made to establish an optimum condition in the surface treatment and curing process. These will be an important parameters for the fabrication of multilayered hybrid composite material, Al 7075 / CFRP CARALL(CARALL: carbon fiber reinforced aluminum laminates). Considering of the above results, 2, 4, 6 and 8 ply CARALL were fabricated with 0.25mm thickness Al 7075-T6 alclad sheet (KAISER Co.), FM 300M adhesive film (CYTEC Co.) and 0.13mm thickness F584-4 carbon epoxy prepreg (HEXEL Co.) in autoclave. Effects of carbon fiber direction and thickness variation in tensile strength were investigated by experiment and theoretical approach. Damage behavior of carbon fiber laminates and CARALL laminates were investigated also. Moreover, in order to study the characteristic of strength decrease by drilling on manufacturing and assembling of aircraft parts, specimen were made with circular hole notch and tested on tensile strength experiment. Characteristic of notch tensile strength and modified failure prediction criterion were reviewed in this experiment. The results are as follows : 1. The PAA (phosphoric acid anodizing process) provided the best adhesive strength among the specimens. On the other hand, the poor adhesive strength was shown on the vapor degreased and CAA (chromic acid anodizing process) and FPL (sulfuric . sodium dichromate acid etching process) was nearly same to the PAA. 2. The adhesive strength of the co-cured Al and carbon fiber prepreg higher than that of secondary cured one. But with respect to the dimensional stability, the secondary curing method was better than co-curing method. In secondary curing method, the condition of 0.35 MPa pressure shown higher adhesive strength than 0.6 MPa pressure condition and it was shown that the increaser curing time, the increaser adhesive strength. The effectiveness of adhesive strength increasing according to curing time was effective in 90 min curing time rather than 120 min curing time. 3. DMA(Dynamic Mechanical Analysis) test revealed T_(g) in curing times over 60 min is nearly same, so it is estimated they will have similar degree of curing and joint durability in using FM300M adhesive film. Considering of the results of the above mention, the condition of 0.35 MPa, 90 min, secondary curing method with PAA treated Al is recommended to fabricate the precise, high adhesive and durable aircraft parts. 4. High strength CARALL hybrid composite was fabricated with thin Al 7075-T6 sheet and adhesive film instead of glass fiber. The effect of strength enhancement was shown in case of using more than 4 ply F584-4 carbon prepreg. 5. As the results of analyzing the state of stress distribution of section of CARALL, by the FEM analysis of CARALL of L(0°) direction, 4 ply, it was found that a partial stress increase in order of epoxy adhesive, Al 7075, CFRP. And the partial stress of CFRP carried out a great portion of applied stress. 6. The real failure strengths of L(0°) direction, 4 ply CARALL were a little lower than theoretical strength by the law of mixture, but in case of 6 and 8 ply CARALL , the strengths were nearly equal to theoretical strength. And in case of 45°and T(90°) direction, the strengths of 2, 4, 6 and 8 ply CARALL were nearly equal to theoretical strength also. So it is estimated CARALL nearly satisfy the law of mixture in spite of fiber direction and thickness. 7. The impact resistance of CARALL was higher than that of CFRP. This is because both side Al sheet of CARALL absorb a great of impact damage. 8. Notch sensitivity of CFRP was decreased by hybriding with the high strength and high notch sensitivity CFRP material and ductile Al 7075. 9. Characteristic length d_(0) was different in Al 7075, CFRP, CARALL and vary with hole diameter 2R and width W. Notch sensitivity coefficient k increase in order of Al 7075, CARALL, CFRP. In same material, coefficient k decrease with increasing width. 10. Kims' modified failure prediction criterion was satisfied in CARALL, CFRP, Al 7075 better than Whitney's criterion. Between characteristic length d_(0) and notch strength, there is in inverse proportion, d□ increase with width W in same notch strength.
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#항공기 구조 A1 7075/CFRP 적층 복합재제조 노치강도
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