The Desirable Condition of the Air-blowing Reaction on Isotropic Pitch Precursor for General Purpose Carbon Fiber

To address the problems of high damage rate, low seeding accuracy, and poor seeding generally in the seeding process, a general-purpose seeding device was designed in this study based on the principle of mechanical pneumatic combined seeding. The air-blowing-type cleaning and seed unloading of the device laid the conditions for precise seeding and flexible seeding. In addition, single-factor experiments were performed on seeds (e.g., soybeans, corn, and rape-seeds) with different particle sizes and shapes to verify the general properties of the seed metering device. A multi-factor response surface optimization experiment was performed by applying soybean seeds as the test object to achieve the optimal performance parameters of the seed metering device. At a seed-clearing air velocity of 16.7 m/s, a seed feeding drum speed of 13.7 r/min, and a hole cone angle of 35.6°, corresponding to the optimal performance index, the qualified index, the replay index, and the missed index reached 97.94%, 0.03%, and 2.03%, respectively. The verification test results are consistent with the optimized ones. As indicated from the results, the seed metering device exhibits good general properties, low damage rate, great precision, and high efficiency; it is capable of meeting general seeding operations of different crop seeds and technically supporting for the reliability and versatility of the seeder.

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High-speed consolidation and repair of carbon fiber/epoxy laminates through ultrasonic vibrations: A feasibility study

Journal of Composite Materials ◽

10.1177/0021998320903097 ◽

2020 ◽

Vol 54 (20) ◽

pp. 2707-2721 ◽

Cited By ~ 1

Author(s):

David Hoskins ◽

Genevieve Palardy

Keyword(s):

Carbon Fiber ◽

High Speed ◽

Vertical Displacement ◽

General Purpose ◽

Void Content ◽

Ultrasonic Vibrations ◽

Cross Sectional ◽

Ultrasonic Consolidation ◽

Vibration Time ◽

Carbon Fiber Epoxy

Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs.

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