The Influences of Projectile Material and Environmental Temperature on the High Velocity Impact Behavior of Triaxial Braided Composites

Abstract

Two-dimensional (2D) triaxial braided composites with braiding angle (± 60°/0°) have been used as aero-engine containing casing material. In the current paper, three types of projectile with the same mass and equivalent diameter, including cylinder gelatin projectile, carbon fiber-reinforced plastics (CFRP), and titanium alloy blade-like projectile, were employed to impact on triaxial braided composites panels with thickness of 4.3 mm at room temperature (20 °C) to figure out the influences of projectile materials on the damage pattern and energy absorption behavior. Furthermore, the influences of environmental temperature were also discussed considering the aviation service condition by conducting ballistic impact tests using CFRP projectile at cryogenic temperature (−50 °C) and high temperature (150 °C). The triaxial braided target panel were pre-heated or cooled in a low-temperature chamber before mounted. It is found that soft gelatin project mainly causes global deformation of the target and therefore absorb much more energy. The triaxial braided composite absorb 77.59% more energy when impacted with CFRP projectile than that with titanium alloy projectile, which mainly results in shear fracture. The environmental temperature has influences on the damage pattern and energy absorption of triaxial braided composites. The cryogenic temperature deteriorates the impact resistance of the triaxial braided composite material with matrix cracking damage pattern, while high temperature condition improves its impact resistance with shearing fracture damage pattern.

Damage Monitoring of Braided Composites Using CNT Yarn Sensor Based on Artificial Fish Swarm Algorithm

“…Assuming that the monitoring area E was digitally discretized into m × n pixels, where the event at which any pixel point S(x, y) was covered by a CNT yarn sensor node i was defined as r i , the probability P{r i } of this event occurring was the probability P cov (x, y, c i ) that the pixel point (x, y) was covered by the sensor node i [47], as shown in Figure 7. Equation (7) indicates that when the distance between pixel point 𝑆(𝑥, 𝑦) and CNT yarn sensor node 𝑖 is less than the sensing range 𝑟, the pixel point 𝑆(𝑥, 𝑦) is considered to be covered by CNT yarn sensor node 𝑖. Equation (7) indicates that when the distance between pixel point S(x, y) and CNT yarn sensor node i is less than the sensing range r, the pixel point S(x, y) is considered to be covered by CNT yarn sensor node i.…”

“…Equation (7) indicates that when the distance between pixel point 𝑆(𝑥, 𝑦) and CNT yarn sensor node 𝑖 is less than the sensing range 𝑟, the pixel point 𝑆(𝑥, 𝑦) is considered to be covered by CNT yarn sensor node 𝑖. Equation (7) indicates that when the distance between pixel point S(x, y) and CNT yarn sensor node i is less than the sensing range r, the pixel point S(x, y) is considered to be covered by CNT yarn sensor node i.…”

“…However, many factors, such as the braiding process, structural parameters, mechanical properties of braided yarn and matrix, void ratios, and interface damage, have important impacts on their structure and mechanical properties [ 3 , 4 , 5 ]. Indeed, 3D braided composites’ parts will suffer various stresses and strains in the process of application, resulting in structural damage, which may lead to various serious accidents and cause huge losses of life and objects and environmental pollution [ 6 , 7 , 8 , 9 ]. As the shape of a 3D braided composite structure hardly changes before failure, it becomes difficult to detect any internal damage through common visual or knock inspections [ 10 , 11 ].…”