Relationship between mechanical-property and energy-absorption trends for composite tubes
U.S. Army helicopters are designed to dissipate prescribed levels of crash impact kinetic energy without compromising the integrity of the fuselage. Because of the complexity of the energy-absorption process it is imperative for designers of energy-absorbing structures to develop an in-depth understanding of how and why composite structures absorb energy. A description of the crushing modes and mechanisms of energy absorption for composite tubes and beams is presented. Three primary crushing modes of composite structures including transverse shearing, lamina bending, and local buckling are described. The experimental data presented show that fiber and matrix mechanical properties and laminate stiffness and strength mechanical properties cannot reliably predict the energy-absorption response of composite tubes.
Design and certification of a composite thin-walled structure for energy absorption
Thin-walled Carbon Fibre Reinforced Polymer (CFRP) energy-absorbing devices have been successfully used in premier racing leagues to drastically improve the crashworthiness of a vehicle. Since their introduction in Formula 1 (F1) in the second half of the 1990s, the Rear Impact (RIMP) attenuators have received particular attention and their utilisation has been documented in scholarly publications. The engineering development and certification of the RIMP of the Star Mazda Racecar is discussed in detail. Quasi-static and dynamic crush tests are performed on two RIMP designs, featuring very different stacking sequences, are experimentally investigated. While the overall behaviour is quite different, they both exhibit the ability to collapse in a stable, progressive fashion. Furthermore, although the overall shape of the load-stroke diagram, energy absorption characteristics and failure behaviour have shown very good agreement, the quasi-static test results tend to substantially overestimate the effective dynamic energy absorption characteristics. The final RIMP design is selected based on its higher energy absorption and friendlier manufacturing characteristics.
Copper Phthalocyanine Improving Nonaqueous Catalysis of Pseudomonas cepacia Lipase for Ester Synthesis
The nonaqueous catalysis of lipases is significant for synthesis of high pure esters, but they usually behave low catalytic activity due to denaturation and aggregation of enzyme protein in organic phases. To improve the nonaqueous catalysis, the inexpensive copper phthalocyanine was taken as a new carrier on which Pseudomonas cepacia lipase was immobilized by physical absorption, and used for synthesis of hexyl acetate, an important flavor, via transesterification of hexanol and vinyl acetate. Results showed that the desired loading was 10 mg lipase immobilized on 10 mg copper phthalocyanine powder. When the immobilized lipase was employed in the reaction system consisted of 1.5 mL hexanol and 1.5 mL vinyl acetate at 37℃ and 160 rpm, the conversion was five fold of that catalyzed by native lipase after 1 h, and reached 99.0% after 8 h. Undergoing six times of 8-h reuses, the immobilized lipase had an activity attenuation rate 1.22% h− 1, lower than 1.77% h− 1 of native lipase, which meant that the immobilized lipase was more stable. Even at the room temperature and the static state without shaking or stirring, the immobilized lipase could bring conversion 42.8% after 10 h and the native lipase gave 20.1%. Obviously, the immobilized lipase is an available biocatalyst in organic phase and has great potential in food industry.