The packing stress of impregnated fiber mats
The packing stress of impregnated fiber mats
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浸渍纤维毡的堆积应力
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Månson
中科院分区：
文献类型：
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作者：
C. Servais;V. Michaud;J. Månson
系统地研究了影响熔体浸渍、树脂传递模塑和模压成型纤维毡堆积应力的工艺参数。一个基于纤维局部弯曲的解析方程被应用于由分散的平面束浸渍熔融的聚丙烯组成的复合垫，该方程以前是针对非浸渍网络推导的。结果表明，在浸渍束垫的包装过程中，特别是当垫子被针刺时，许多同时发生的机制相互作用。这些问题包括束的面内弯曲、束内纤维的紧实以及面外纤维的屈曲、滑脱或断裂。为了识别和分离这些特征，束的纵横比、润滑剂、针刺强度和包装历史都是不同的。还进行了微观结构实验，以评估束状铺展的程度。结果发现，分散的纤维或束大致遵循基于局部弯曲的方程，但针状束网络偏离了幂定律的行为。确定了三个区域。第一个原因是由于垫子的自加载和面外纤维的屈曲。第二个区域是由于面外纤维的滑移和断裂，并且取决于加载历史和针刺强度。第三个区域是由于面内纤维束的堆积，在载荷作用下，这些纤维束并不真正弯曲或展开，但由于形成纤维束的单个纤维的不对准和波浪度，这些纤维束是局部可压缩的。在压缩成型中，观察到初始面外束面内再取向对堆积应力的影响。
The parameters affecting the packing stress of fiber mats for melt impregnation, resin transfer molding and compression molding are systematically investigated. An analytical equation based on local bending of fibers, which was previously derived for non-impregnated networks, is applied to composite mats of dispersed planar bundles impregnated with molten polypropylene. It is shown that many simultaneous mechanisms interact during packing of impregnated bundle mats, in particular when the mats are needled. These include in-plane bending of the bundles, compaction of the fibers within a bundle, and buckling, slippage or breakage of the out-of-plane fibers. In order to identify and decouple these features, aspect ratio of the bundles, lubrication, needling intensity and packing history are varied. A microstructural experiment is also developed to evaluate the extent of bundle spreading. It is found that dispersed fibers or bundles roughly follow the equation based on local bending, but that needled bundle networks deviate from the power law behavior. Three regions were identified. The first is attributed to self-loading of the mats and to buckling of the out-of plane fibers. The second region is due to slippage and breakage of the out-of-plane fibers and depends on the loading history and on the needling intensity. The third region is due to packing of the in-plane bundles, which do not really bend, or spread under load, but are locally compressible, owing to misalignment and waviness of the individual fibers forming the bundles. In compression molding, the influence of the in-plane reorientation of the initially out-of-plane bundles on the packing stress is observed.