Energy transport mechanisms and their impact on the matrix damage during pulsed laser processing of carbon fiber reinforced plastics

碳纤维增强塑料（CFRP）的强不均匀结构有利于材料的热损伤，因此意味着这种材料的激光材料加工特别困难。造成热损伤的主要原因是碳纤维具有良好的导热性。热量从相互作用区流入化合物，造成基体损伤。然而，这并不是导致CFRP材料热损伤的唯一机制。其他能量再分配机制，如激光辐射在碳纤维圆截面上的反射、热烧蚀产物和氧化也影响材料的热损伤。在本项目的框架内，将量化脉冲激光加工CFRP时影响入射能量插入和再分配的物理过程。计划考虑下列影响：(i)沿着碳纤维导热进入化合物时的热积累效应；（ii）由于材料结构不均匀，在激光加工过程中会反射激光辐射；（三）热蒸汽/等离子体膨胀引起的热传递；（四）由于材料氧化而产生的额外能量输入和对烧蚀的影响。大多数这些影响并不仅仅发生在碳纤维增强塑料的加工过程中，但由于材料的非均匀结构，它们在这种情况下变得特别明显。因此，从实验和理论上区分和量化不同的效应成为可能。

The strongly inhomogeneous structure of carbon fiber reinforced plastics (CFRP) facilitates thermal damaging of the material and therefore implies particular difficulties for laser materials processing of this material. A major cause for the thermal damage is the good heat conductivity along the carbon fibers. Heat flows from the interaction zone into the compound where it causes matrix damage. However, this is not the only mechanism which leads to thermal damage of the CFRP compound. Other energy redistribution mechanisms such as reflection of laser radiation at the round cross section of the carbon fibers, hot ablation products and oxidation also influence the thermal damaging of the material. In the frame of this project the physical processes which influence the insertion and redistribution of the incoming energy during pulsed laser processing of CFRP will be quantified. It is planned to consider the following effects:(i) Heat accumulation effect in the case of heat conducting along the carbon fibers into the compound;(ii) Reflection of laser radiation during laser processing due to the inhomogeneous material structure;(iii) Heat transport due to the expansion of hot vapor / plasma;(iv) Additional energy input and influences on ablation due to oxidation of the material.Most of these effects do not occur solely during the processing of CFRP but they become especially evident in this case because of the inhomogeneous structure of the material. Therefore an experimental and theoretical distinction and quantification of the different effects becomes possible.