Study On Thermal Damage And Its Effect On Mechanical Properties In Fiber Laser Cutting CFRP Laminate

CFRP composite has become the popular material in the field of light weight due to its high specific strength,strong designability,good impact resistance and corrosion resistance.For the application of CFRP,cutting technology is very important since cutting quality directly determines the assembly accuracy and performance of CFRP parts.Laser cutting CFRP can overcome the tool wear,material delamination,edge burr and other defects which are common defects in traditional mechanical cutting,and has advantages in processing cost,efficiency and quality.In laser cutting,however,it is easy to cause great thermal damage that greatly reduces the cutting quality because of the high energy of the laser beam and the great difference in thermal properties between CFRP components.In this paper,theoretical and experimental studies were carried out to study the thermal damage from three aspects:characterization of thermal damage,determination of the influence of process parameters on thermal damage,and exploration of the influence of thermal damage on tensile mechanical properties.The main research results are as follows:（1）The surface morphology and the thermal damage of entry surface,exit surface,profile and cutting surface in the three different CFRP lamination were observed.The influence of layer configuration on thermal damage was determined,and the formation mechanisms of different thermal damage were explained.Besides,the heat affected zone（HAZ）of linear cutting was quantitatively characterized from three angles,and the advantages and disadvantages of the three quantization methods were compared.The study found that thermal damage in[+45°/-45°]_2SS CFRP laminate are relatively small,and it was more accurate to quantify HAZ from the exit surface and section of the kerf.（2）Based on previous research,the thermal damage of laser cutting hole in[+45°/-45°]_2SS CFRP laminate was studied.On the basis of theoretical analysis,a simple elliptical method was established to quantify the heat affected zone around the hole,and the reliability of the method was verified.The influence of line energy（laser power divided by laser speed）on the heat affected zone around the hole was summarized from the quantization results.They showed an approximate logarithmic relationship.With the increase of line energy,the heat affected zone first increased rapidly,then gradually slowed down,and finally tended to a certain value.（3）The effects of thermal damage around the hole on tensile strength and strain field around the hole were studied.The results showed that the larger thermal damage did not reduce the tensile strength of the perforated part,but it significantly increased the strain of the samples.The closer the hole is,the more significant the aggravation effect is.Besides,the aggravation effect increases gradually with the increase of tensile stress.The research results of thermal damage in this paper provide the experimental and theoretical basis for the quality evaluation system and process optimization of laser cutting CFRP laminates and can promote the application of high power fiber laser cutting technology in the CFRP composite material processing field.