基于应变Hashin准则的CFRP层合板螺旋铣孔渐进损伤仿真分析

Simulation analysis of progressive damage of helical milling holes in CFRP laminates based on strain Hashin criterion

  • 摘要: 由于碳纤维增强复合材料(Carbon Fiber Reinforced Plastic/Polymer, CFRP)层合板在螺旋铣孔过程中呈现多种失效形式共存的渐进损伤,导致其基于Hashin准则应力形式的有限元仿真精度难以保证。本文通过引入应变修正了Hashin准则,并将其应用于CFRP层合板螺旋铣孔仿真。结果表明,应变Hashin准则下的应力与应变峰值能够达到较高水平,且入/出口处的孔径偏差较修正前分别减小了36%与43%,表明该准则能够完整反映“裂纹萌生-扩展-失效”的连续损伤演变过程。进一步应用应变Hashin准则探究纤维方向对制孔质量的影响,发现0°时的平均切削力、入口损伤因子与孔径偏差可达最小值,分别为39.52 N、0.21与12 μm;90°对应的平均切削力为最大值可达52.12 N;135°时的出口损伤因子与孔径偏差可达最大值,分别为0.28与27 μm。最后经试验验证,应变Hashin准则下的轴向力Fz与周向力Fr预测误差较小,分别为6.4%与12.7%,且其孔入/出口形貌以及孔壁质量与试验结果具有较好的一致性。相比于传统Hashin准则应力形式,应变Hashin准则基于应变积累逐步判定损伤失效,有效抑制了CFRP螺旋铣孔中因应力集中造成的过早失效,从而显著提高仿真预测精度。

     

    Abstract: Due to the progressive damage involving multiple coexisting failure modes during the helical milling of carbon fiber reinforced polymer (CFRP) laminates, the finite element simulation accuracy based on Hashin criterion stress form is difficult to guarantee. In this study, the Hashin criterion was modified by introducing strain and applied to the simulation of helical milling of CFRP laminates. The results show that the stress and strain peaks under the strain Hashin criterion can reach a high level. The aperture deviation at the entrance/export is reduced by 36% and 43% respectively compared with that before correction, which indicates that the criterion can fully reflect the continuous damage evolution process of “crack initiation-propagation-failure”. The strain Hashin criterion is further applied to explore the influence of fiber orientation on the hole quality. It is found that the average cutting force, entrance damage factor and aperture deviation can reach the minimum values at 0°, which are 39.52 N, 0.21 and 12 μm, respectively; The average cutting force corresponding to 90° is up to 52.12 N; The export damage factor and aperture deviation at 135° can reach the maximum values of 0.28 and 27 μm, respectively. Finally, it is verified by experiments that the prediction errors of axial force Fz and circumferential force Fr under the strain Hashin criterion are small, which are 6.4% and 12.7% respectively. And its hole entrance/export morphology and hole wall quality are in good agreement with the experimental results. Compared with the traditional Hashin criterion stress form, the strain Hashin criterion gradually determines the damage failure based on strain accumulation, which effectively suppresses the premature failure caused by stress concentration in CFRP helical milling holes, thus significantly improving the prediction accuracy of its simulation.

     

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