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Thermal defect characterization and heat conduction modeling during fiber laser cutting carbon fiber reinforced polymer laminates

Chen Limei, Li Maojun, Yang Xujing, Li Bin

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 2

453--466

High-power fiber laser has been proven to be feasible for cutting carbon fiber reinforced polymers with several advantages including noncontact force, high efficiency and flexibility, while the characteristics of thermal damage and heat conduction in materials are not yet fully understood. Continuous-wave fiber laser was applied in this work to cut 2.0-mm-thick carbon fiber reinforced polymer laminates with different layup configurations. The influence of processing parameters including laser power and cutting speed on thermal damage was investigated. The characteristics of various thermal defects on different positions of machined surface were analyzed using high-resolution SEM and mathematical models. Interestingly, swollen fibers were observed and they connected together to form irregular swollen masses. According to further analysis on the initial heat distribution, it showed that cutting speed was the main factor affecting heat accumulation. In addition, modified heat conduction model was developed to analyze heat transfer within unidirectional carbon fiber reinforced polymer laminates in comparison with experimental results, which can be applied to predict heat affect zone during high-power fiber laser cutting composite materials.

Thermal damage of CFRP laminate in fiber laser cutting process and its impact on the mechanical behavior and strain distribution

Li Maojun, Gan Guocui, Zhang Yi, Yang Xujing

Archives of Civil and Mechanical Engineering

2019

Vol. 19, no. 4

1511--1522

Fiber laser cutting is a promising alternative to the conventional methods in machining CFRP with high efficiency, while the influence of machined quality on strain distribution and mechanical behavior of CFRP laminates is yet not fully understand. The aim of this paper is to study the effect of laser cutting parameters on thermal defects and related mechanical performance. DIC technique was successfully employed to assess full-field strain distribution under tensile loading. The relationship between strain distribution and failure evolution/mode was also investigated. Results showed that various thermal defects including matrix recession, resin decomposition, fiber burrs and delamination were observed on entry and exit surfaces, while microcracks, cavities and striations were prevalent on machined surface. Tensile strength of CFRP laminate with open hole was highly related to applied laser processing parameters. DIC technique indicated that the crack propagation and failure mode were in good agreement with the high level of strains developed around the hole. Matrix-fiber interface cracking, fiber breakage and splitting were the main failure modes at test cessation.