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Open AccessArticle

Experimental Study of the Effect of Internal Defects on Stress Waves during Automated Fiber Placement

1
School of Mechatronics Engineering, Harbin Institute of Technology, No. 92, Xidazhi Street, Harbin 150001, China
2
SAIC Motor Passenger Vehicle Company, No. 201, An Yan Road, Shanghai 201804, China
*
Author to whom correspondence should be addressed.
Polymers 2018, 10(4), 413; https://doi.org/10.3390/polym10040413
Received: 28 February 2018 / Revised: 3 April 2018 / Accepted: 4 April 2018 / Published: 9 April 2018
(This article belongs to the Special Issue Polymer Hybrids and Composites)
The detection technique of component defects is currently only realized to detect offline defects and online surface defects during automated fiber placement (AFP). The characteristics of stress waves can be effectively applied to identify and detect internal defects in material structure. However, the correlation mechanism between stress waves and internal defects remains unclear during the AFP process. This paper proposes a novel experimental method to test stress waves, where continuous loading induced by process itself is used as an excitation source without other external excitation. Twenty-seven groups of thermosetting prepreg laminates under different processing parameters are manufactured to obtain different void content. In order to quantitatively estimate the void content in the prepreg structure, the relation model between the void content and ultrasonic attenuation coefficient is revealed using an A-scan ultrasonic flaw detector and photographic methods by optical microscope. Furthermore, the high-frequency noises of stress waves are removed using Haar wavelet transform. The peaks, the Manhattan distance and mean stress during the laying process are analyzed and evaluated. Partial conclusions in this paper could provide theoretical support for online real-time detection of internal defects based on stress wave characteristics. View Full-Text
Keywords: carbon fiber reinforced thermoset composites; automated fiber placement (AFP); stress wave; defects carbon fiber reinforced thermoset composites; automated fiber placement (AFP); stress wave; defects
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MDPI and ACS Style

Han, Z.; Sun, S.; Li, W.; Zhao, Y.; Shao, Z. Experimental Study of the Effect of Internal Defects on Stress Waves during Automated Fiber Placement. Polymers 2018, 10, 413.

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