Mechanism of effect of processing parameters on stress wave propagation characteristics during automated fiber placement
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摘要: 利用应力波特征能够有效识别材料结构中内部缺陷及其分布形式,为了将工艺载荷作为应力波激励源对预成型体内部缺陷进行识别,应首先研究铺丝过程中工艺参数对应力波传播特征的影响,以确定应力传感器的放置位置。本文采用有限元方法构建了铺丝过程热力耦合模型,分析了应力波特征参数与工艺参数之间的关系,并进行了实验验证。为了从微观能量角度解释工艺参数对应力波特征的影响规律,采用分子动力学方法,建立了预浸丝界面的分子模型,并计算出总能量、纤维表面能、基体内能等能量参数,识别和评价了不同工艺参数作用下的应力波驱动能量及其贡献比,以揭示工艺参数对应力波特征的能量作用机制。结果表明,以基体内能作为驱动能量的侧向应力波与工艺参数的关系明显,在不同工艺参数施载下,内部缺陷的形成对该波形的作用易于识别,该结论可作为应力传感器放置位置的参考依据。Abstract: The internal defects in the material structure and their distributions could effectively be identified by using stress wave characteristics. In order to identify the internal defects of the preform by using processing loads that act as a stress wave excitation source, the effect of the processing parameters on the stress wave propagation characteristics in the laying process should be first studied to determine the position of the stress sensor. In this paper, the thermo-mechanical coupling model of the laying process was constructed by using the finite element method (FEM). The relationship between the stress wave characteristic parameters and the processing parameters was analyzed, and the experimental verification was then carried out. In order to explain the effect of the processing parameters on the stress wave characteristics from the perspective of microscopic energy, molecular dynamics (MD) method was used to establish the molecular model of the prepreg interface, and the energy parameters such as total energy, surface energy of fibers, and internal energy of matrix were calculated. Furthermore, the driving energy of stress wave and its contribution ratio under different processing parameters were identified and evaluated to reveal the energy effect mechanism of the processing parameters on the stress wave characteristics. The results show that the lateral waves driven by the internal energy of matrix have a significant relationship with the processing parameters. The effect of the formation of internal defects on the waveform is easy to identify under the different processing parameters. This conclusion could be used as a reference for stress sensor placement.
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Key words:
- composites /
- automated fiber placement /
- stress wave propagation /
- processing /
- microscopic analysis
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