Detailed knowledge of the local fiber orientation and the local fiber volume content within composite parts provides an opportunity to predict the structural behavior more reliably. Utilizing forming simulation methods of dry or pre-impregnated fabrics allows for predicting the local fiber orientation. Additionally, during the forming process, so-called draping effects like waviness, gapping or shear-induced transverse compression change the local fiber volume content. To reproduce and investigate such draping effects, different manufacturing tools have been developed in this work. The tools are used to create fabric samples with pre-defined deformation states, representing the different draping effects. The samples are evaluated regarding the resulting fiber volume content. The experimental results are compared with the predictions of an analytical solution and of a numerical solution based on draping simulation results. Furthermore, the interaction of the draping effects at arbitrary strain states is discussed regarding the resulting fiber volume content.

Unidirectional non-crimp fabrics (UD-NCF) are often used to exploit the lightweight potential of continuous fiber reinforced plastics (CoFRP). During the draping process, the UD-NCF fabric can undergo large deformations that alter the local fiber orientation, the local fiber volume content (FVC) and create local fiber waviness. Especially the FVC is affected and has a large impact on the mechanical properties. This impact, resulting from different deformation modes during draping, is in general not considered in composite design processes. To analyze the impact of different draping effects on the mechanical properties and the failure behavior of UD-NCF composites, experimental results of reference laminates are compared to the results of laminates with specifically induced draping effects, such as non-constant FVC and fiber waviness. Furthermore, an analytical model to predict the failure strengths of UD laminates with in-plane waviness is introduced. The resulting stiffness and strength values for different FVC or amplitude to wavelength configurations are presented and discussed. In addition, failure envelopes based on the PUCK failure criterion for each draping effect are derived, which show a clear specific impact on the mechanical properties. The findings suggest that each draping effect leads to a “new fabric” type. Additionally, analytical models are introduced and the experimental results are compared to the predictions. Results indicate that the models provide reliable predictions for each draping effect. Recommendations regarding necessary tests to consider each draping effect are presented. As a further prospect the resulting stiffness and strength values for each draping effect can be used for a more accurate prediction of the structural performance of CoFRP parts.

Одним из основных методов определения проницаемости коллектора в процессе разработки месторождений углеводородов являются гидродинамические исследования скважин. Однако их масштабное проведение зачастую затруднено по причинам технологического и экономического характера. В этой связи в настоящее время получили развитие методы определения фильтрационных параметров, не требующие продолжительной остановки скважин, например метод стабилизации давления и метод анализа добычи. Данные методы получили широкое распространение во многих нефтедобывающих регионах, в том числе в Пермском крае. Имеющийся накопленный опыт данных исследований обусловливает необходимость оценки достоверности демонстрируемых результатов, чему посвящена настоящая статья. Для решения поставленной задачи использованы данные по скважинам, на которых проведены исследования методами восстановления и стабилизации давления, а также имеются регулярные измерения показателей эксплуатации (дебита, забойного давления). Для оценки достоверности определения проницаемости каждым из, по сути, косвенных методов использованы инструменты математической...