Effect of gap and overlap on mode Ⅱ interlaminar fracture toughness of automated fiber placement prepreg laminates

Automated Fiber Placement(AFP) technology facilitates the manufacturing process of composite structures with complex geometry owing to its high efficiency and accuracy.However,the unavoidable imperfections induced by the automated layup method bring challenges to the stability of the final mechanical properties of composites.The influence of AFP-induced gaps and overlaps on the mode Ⅱ interlaminar fracture process of oven-cured laminates is experimentally investigated and explicitly revealed.End...     

变刚度纤维曲线铺放复合材料层合板的有限元建模和拉伸特性分析

通过对变刚度铺放路径进行数学建模,得到变刚度复合材料层合板的拓扑构型,对复合材料层合 板内每个离散单元的每个铺层进行纤维角度和铺层厚度的独立设计。然后将拓扑构型数据导入有限元分析软 件GENESIS 中,实现层合板铺层信息的可视化显示和拉伸性能的分析,得出层合板的弹塑性本构关系。通过 仿真数据与实验测试数据进行对比,得出在所构建的变刚度复合材料层合板模型上进行拉伸实验仿真的准确 度可达95% 。该方法不仅可以可视化地展现出铺放过程中发生重叠的位置、整个复合材料层合板的厚度分布 以及每层上铺放角的分布,还可对其在弹塑性范围内的拉伸性能进行精确仿真。     

SiC_(f)/SiC复合材料铣削加工表面质量北大核心CSCD

使用PCD立式铣刀对聚合物浸渍裂解法(PIP)制备的SiC_(f)/SiC复合材料开展单因素铣削试验,通过对加工中产生的切削力和加工后的表面粗糙度进行测量,分析了铣削工艺参数对其的影响;对加工表面、纤维断口进行SEM分析,讨论了SiC_(f)/SiC复合材料加工表面的形成。研究结果表明,表面粗糙度与切削力的变化趋势相同,高主轴转速和小切削宽度有利于得到表面粗糙度较小的加工表面;近孔洞区域与远离孔洞区域的材料去除方式不同;材料中纤维发生面内偏移和层间屈曲,纤维存在多种去除方式。     

轮盘模拟件破裂试验及其有限元描述

建立了与材料延伸率相关的轮盘破裂准则。以某型发动机低压压气机第1级轮盘为研究对象,模拟轮盘工作时榫槽底的应力分布,设计制造了模拟试件,并在材料试验机上对2个模拟试件进行了试验;借助MSC.MARC商用有限元软件,应用弹塑性、大应变、大变形的非线性有限元方法,描述了轮盘模拟件破裂试验的过程。经验证,计算结果和试验结果相一致。     

Macro-phenomenological high-strain-rate elastic fracture model for ice-impact simulations

The ice impact can cause a severe damage to an aircraft’s exposed structure, thus, requiring its prevention. The numerical simulation represents an effective method to overcome this challenge. The establishment of the ice material model is critical. However, ice is not a common structural material and exhibits an extremely complex material behavior. The material models of ice reported so far are not able to accurately simulate the ice behavior at high strain rates. This study proposes a novel high-precision macro-phenomenological elastic fracture model based on the brittle behavior of ice at high strain rates. The developed model has been compared with five reported models by using the smoothed particle hydrodynamics method so as to simulate the ice-impact process with respect to the impact speeds and ice shapes. The important metrics and phenomena (impact force history, deformation and fragmentation of the ice projectile and deflection of the target) were compared with the experimental data reported in the literature. The findings obtained from the developed model are observed to be most consistent with the experimental data, which demonstrates that the model represents the basic physics and phenomena governing the ice impact at high strain rates. The developed model includes a relatively fewer number of material parameters. Further, the used parameters have a clear physical meaning and can be directly obtained through experiments. Moreover, no adjustment of any material parameter is needed, and the consumption duration is also acceptable. These advantages indicate that the developed model is suitable for simulating the ice-impact process and can be applied for the anti-ice impact design in aviation.