Z-pins对层合复合材料非对称分层增韧作用参数分析——Ⅱ型层间韧性

利用纤维Z-pins的细观力学模型构造了相应的Z-pin单元，结合考虑一阶剪切变形的梁单元，建立了用于分析含非对称分层采用Z-pins增韧的端部开口弯曲试件(End notched flexure，ENF)的有限元模型，并在分层裂纹面上引入接触单元以防止分析过程中2个分层子梁在端部开口处的相互嵌入。通过数值算例分析了Z-pins对含非对称分层的ENF试件Ⅱ型层间韧性的增强作用。参数分析表明，当分层位置靠近层合板的表面时，Z-pins的增韧作用明显下降，Z-pins对Ⅱ型层间韧性的增强作用主要由2个分层子层中较薄子层决定，但另一分层的厚度也对Ⅱ型层间韧性有一定的影响。

Parametric analysis of enhancement of Z-pins on asymmetric delamination of Z-pinned laminated composites--Mode Ⅱ delamination toughness

It was assumed that the friction between the fiber Z-pins and the surrounding matrix，during its pull-out process，provides the bridging forces to enhance the delamination toughness of the laminates. Based on the currently available Z-pin micro-model，a Z-pin element was developed and a beam element model was proposed in this paper to study the effect of Z-pins on modeⅡdelamination toughness of Z-pinned end notched flexure (ENF) specimens. A contact element was also introduced on the delamination crack surface in the proposed finite element model to avoid the unrealistic penetration of the two substrate beams. The numerical results showed that the Z-pins can significantly improve the modeⅡdelamination toughness of the Z-pinned laminated ENF specimens. However，fewer enhancements on modeⅡdelamination toughness are obtained when the delamination crack is close to the surface of ENF specimens. The thickness of the thinner substrate beam is the key parameter to determine the enhanced modeⅡdelamination toughness of ENF specimens.