Opposed-flow flame spread over carbon fiber reinforced plastic under variable flow velocity and oxygen concentration: The effect of in-plane thermal isotropy and anisotropy
Opposed-flow flame spread over carbon fiber reinforced plastic under variable flow velocity and oxygen concentration: The effect of in-plane thermal isotropy and anisotropy
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DOI：
10.1016/j.proci.2020.06.380
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发表时间：
2021-04-10
影响因子：
3.4
通讯作者：
Takahashi, Shuhei
中科院分区：
文献类型：
--
作者：
Kobayashi, Yoshinari;Terashima, Kaoru;Takahashi, Shuhei
本文研究了碳纤维增强塑料（CFRPs）上的对流火焰传播，重点研究了碳纤维（CF）取向对平面内热各向同性和各向异性的影响。采用单向碳纤维布沿不同方向叠层的方法制备了不同碳纤维取向的碳纤维增强复合材料（CFRP）片材，并通过改变气流速度和氧气浓度的烟囱进行燃烧。浮流条件下的极限氧浓度（O2）随CF取向角的增大而显著增大。在超过45度时，即使在60%O-2的情况下，火焰也根本没有蔓延，而是在点燃后立即熄灭。进一步研究了具有0度、15度和30度CF取向角的CFRP的可燃性，其中改变了对向流速和氧气浓度。在所有测试的反向流速下，无论CF方向如何，CFRP的剪切强度均高于聚甲基丙烯酸甲酯（PMMA）。反流速度的响应随CF取向角的变化而变化。在0度时，氧饱和度对反向流速并不过分敏感，但在31%O-2时几乎是恒定的。同时，在15 °和30 °处的LOC随着对向流速度的增加而线性减小。由于碳纤维的高导热性，CFRP的火焰传播速度比PMMA快得多。碳纤维布的火焰传播速率受碳纤维取向的影响，在0 °时的火焰传播速率最大。用于可视化火焰传播过程中的面内温度分布的IR图像显示，预热区域根据CF取向显著变化。因此，不同的CF取向导致面内热各向异性，导致在燃烧和火焰传播速率的差异。本文的研究结果有助于我们评估CFRP的火灾危险性和危害性，并有助于讨论其他各向异性材料的火焰传播行为。(C)2020年燃烧研究所。爱思唯尔公司出版All rights reserved.
This work explores opposed-flow flame spread over carbon fiber reinforced plastics (CFRPs) with an emphasis on the in-plane thermal isotropy and anisotropy depending on carbon fiber (CF) orientation. CFRP sheets with different CF orientations were fabricated by laminating unidirectional prepregs in different directions and combusted via a chimney where flow velocity and oxygen concentration were variable. The limiting oxygen concentration (LOC) under buoyant flow significantly increased with CF orientation angle. At more than 45 degrees, a flame did not spread at all but was extinguished immediately after ignition even at 60% O-2. The flammability of CFRPs with CF orientation angles of 0 degrees, 15 degrees, and 30 degrees was further investigated with varying opposed-flow velocities and oxygen concentrations. The LOC of CFRP was higher than that of polymethyl methacrylate (PMMA) over all tested opposed-flow velocities regardless of CF orientation. The response of LOC to opposed-flow velocity varied with CF orientation angle. At 0 degrees, the LOC was not overly sensitive to opposed-flow velocity but almost constant at 31% O-2. Meanwhile, the LOCs at 15 degrees and 30 degrees linearly decreased with increased opposed-flow velocity. Flame spread for CFRP was much faster than that for PMMA because of the high thermal conductivity of carbon fibers. The flame spread rate of CFRPs was affected by CF orientation and that at 0 degrees was highest among the three tested CFRP sheets. IR images used to visualize the in-plane temperature distribution during flame spread showed that the preheat region was significantly varied according to CF orientation. Varying CF orientation, therefore, causes the in-plane thermal anisotropy, resulting in the differences in the LOC and flame spread rate. The findings from this work help us evaluate the fire risk and hazard of CFRP and serve to discuss flame spread behaviors of other anisotropic materials. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.