Boulet Pascal, Brissinger Damien, Collin Anthony, Acem Zoubir, Parent Gilles
LEMTA, Université de Lorraine CNRS, 2 avenue de la Forêt de Haye - TSA 60604, Vandoeuvre les Nancy cedex 54518, France.
Materials (Basel). 2015 Aug 21;8(8):5398-5413. doi: 10.3390/ma8085251.
The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90-0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.
讨论了材料降解过程中吸收率的变化，并研究了其作为降解模型中相关参数之一的影响。使用三种行为差异很大的材料来证明其作用：一种是不透明的、几乎呈灰色的碳复合材料，一种是不透明且依赖光谱的胶合板板，还有一种是半透明的透明聚甲基丙烯酸甲酯板。分析了原始材料和热降解不同阶段的降解材料的数据。可以看出，在受到显著热侵蚀后，吸收率和发射率通常会达到0.90 - 0.95范围内的高值，且具有近灰色行为，但根据所关注的材料不同，可能首先会观察到一些显著变化，尤其是在降解的早期阶段。额外的不准确性可能来自平板上入射通量的不均匀性。总体而言，根据降解时间的不同，吸收通量可能会出现高达20%的差异，这主要是由于吸收的光谱变化所致；根据平板上的位置不同，差异可能会再增加10%。因此，具有恒定且唯一吸收率值的简单模型可能会导致辐射通量吸收评估不准确，这可能会对热解分析产生影响，特别是对于与降解过程早期阶段相关的特性，例如着火时间。
