Numerical Research On The Macro-mecro Effect Of Laser Irradiation To Fibrous Composites

Along with the rapid development of laser and composites, more and more subjects on the interaction of laser and composites are appeared in lots of spheres such as national defence, industry and physic. However, because of the shorter pulse, higher intensity, smaller scale and higher demand of the precision, the macro method could no more meet the requirements. Therefore, it is necessary to do some research in the scale of mecro and micro.Based on the analysis of the background and the summarization of the theory on the interaction of laser and material, a physics model was set up according to the special structure of fibrous composites. The model included the processes of heat transfer, phase change and plume spurting. Using the computer language of Fortran and APDL (ANSYS Parameter Design Language), I composed a program to simulate the macro-mecro effect of laser irradiation to fibrous composites.According to the degree of the difference between fiber and matrix, two set of parameters were considered in different models. According to the permutation of fibers four models were calculated: one fibrous bundle horizontally located model, one fibrous bundle vertically located model, two fibrous bundles model and four fibrous bundles model. Heat enthalpy method and ANSYS element birth and death technique were adopted to calculate the ablation profile, temperature field, stress field and mass ablation rate. Based on the result, some conclusions of the interaction characters were obtained. There research showed that the heat transfer direction was from matrix to fiber near the surface of ablation, the deeper section was opposite. Secondly, the trend of mass ablation rate was opposite to the rate of the bare fiber area in the whole ablated surface. What's more, because of heat softened, the sphere of the maximum stress was appeared next to the position of the maximum strain.By calculating the irradiating effect of different laser intensities, the affect of the laser intension was discussed. According to the discussion, the intensity was higher the effect of asymmetric was greater. In the range from 108W/m2 to 1010W/m2 thought over in this paper, the mass ablation rate was pro rata with the laser intensity approximately. The fibrous bundles in the ablation played the role of heat pump, adjusting the consumed power of the matrix. The intensity was simaller the effect of the pump was more remarkable.The plume spurting was simulated to get the spacial distributing of the state parameters. By analyzing the plume's absorption cross-sections, the effect of plume shielding was investigated. The simulated results revealed that the spurting led to a shock wave promulgating in the surrounding air. The main impact of plume was the heat-preservation effect, the fed back effect was too small to ignore. In order to fit the industry requirements, it's better to adopt the macro method the whole field and use the mecro method to affirm in the pivotal sphere. For discussing the effect of mecro structure to macro ablation property, a set of simulations were done to check the role of mixture. Based on the simulated results, the role fit better when the intensity was higher, the components were more similar and the volume rate of fiber was smaller.