基于CFRP切削过程仿真的面下损伤形成分析

由于碳纤维增强树脂基复合材料(Carbon fiber reinforced plastic,CFRP)宏观上呈现非均质、各向异性,细观上表现为纤维和树脂的特殊混合形态,导致其制件加工过程中极易产生分层、开裂等损伤,严重影响其制件的加工精度及承载性能。研究CFPR加工损伤产生机理并以此降低加工损伤是提高其加工质量的关键。基于宏观各向异性本构、Hashin失效起始准则及损伤演化,建立了可实现任意纤维角度单向板连续动态切削过程仿真分析的直角切削有限元模型,分析了任意纤维角度CFRP单向板连续切削过程面下损伤,得到了纤维角度、切削参数、刀具结构对面下损伤深度的影响规律。具体结果:纤维角度为影响面下损伤的主要因素,随纤维角度增大,切削力增大同时面下损伤深度也明显增加;面下损伤的主要原因为切削力过大导致的基体破坏及扩展;对于135°单向板面下损伤深度随刀具前角增大呈先增大后减小的趋势。

FEM Simulation Analysis of Subsurface Damage Formation Based on Continuously Cutting Process of CFRP

On account of heterogeneous and anisotropic nature of the carbon fiber reinforced plastic (CFRP) in macroscopy and a special state of fiber-resin mixture in microscopy, delamination, cracks, etc. are easily generated in the manufacturing process, which greatly reduces the bearing capacity and machining accuracy of final parts. The key to improve machining quality lies in exploring the mechanism of CFRP subsurface damages for the purpose of damage reduction. In this paper, the orthogonal cutting simulation model that can realize the unidirectional CFRP continuously dynamic cutting process at any fiber orientation is developed based on macroscopic anisotropy constitutive behaviors, Hashin initial failure criterion and the damage evolution. Also analysis of subsurface damages in the unidirectional CFRP continuously dynamic cutting process of is made to acquire influences of fiber orientation, cutting parameters and tool geometries on the damage depth. Detailed results are listed as follows: Subsurface damages are mainly impacted by fiber orientation, and with the increase of the orientation, the cutting force rises, and so is the damage depth. The mechanism of subsurface damages is matrix fractures led by excessive cutting force and the resulting damage propagation; the damage depth first increases and then decreases with the augment of the tool rake angle for unidirectional CFRP with 135° fiber orientation.