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Impact Behavior of Carbon and Hybrid Carbon-Glass Laminates at Low Temperatures



Carbon fibre laminates and hybrid carbon/glass fibre laminates are used mainly in aerospace engineering and space vehicles. The structures made of this material may be subjected to different impacts when in service. The working conditions is far from being at room temperature, airplanes operates mainly at low exterior temperatures as -60ºC and space vehicles are exposed at even lower ones. This research project deals with the impact performance of different laminates. A hybrid glass/carbon-epoxy composite similar to those used by the most modern planes in the border of attack of the wings has been studied from room temperature to -60ºC. Additionally a carbon-epoxy composite has been studied in the same range of temperatures and even tested at -196ºC using liquid nitrogen as coolant. The laminates have been tested from room temperature to low ones under impact conditions using a gas gun, with 5.5 mm diameter steel spherical projectiles. After completion of tests, the extent of damage was measured by means of ultrasonic C-scan inspection. The ballistic curves and the drop velocity curves obtained from those tests show a marked influence of the temperature on the results. To study the possible damage introduced on the laminates due to its exposition at low temperatures, also a temperature cycle was applied to different laminates and tested afterwards at room temperature, showing that the temperature cycle does not damage the laminates. This result confirms that the impact results at low temperature shows the impact performance at different temperature, as the exposition at different temperatures does not affect the results. A Lambert-Jonas fit curve for the different laminates is presented. The ballistic limit at different temperatures has also been obtained, and its variation is formulated for the carbon laminates.

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