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)的强烈不均匀结构促进了材料的热损伤，因此给激光材料的加工带来了特别的困难。热损伤的一个主要原因是碳纤维沿线具有良好的导热性能。热量从相互作用区流入化合物，在那里会造成基质破坏。然而，这并不是导致碳纤维复合材料热损伤的唯一机理。激光辐射在碳纤维圆形截面上的反射、热烧蚀产物和氧化等能量再分配机制也影响材料的热损伤。在本项目的框架内，将量化在脉冲激光加工碳纤维增强塑料过程中影响入射能量插入和重新分布的物理过程。计划考虑以下影响：(I)热传导到化合物中时的热积累效应；(Ii)由于材料结构不均匀而在激光加工过程中反射激光辐射；(Iii)热蒸汽/等离子体膨胀引起的热传输；(Iv)由于材料氧化而产生的额外能量输入和对烧蚀的影响。大多数这些影响不只发生在碳纤维复合材料的加工过程中，但在这种情况下，由于材料的不均匀结构，这些影响变得特别明显。因此，从实验和理论上区分和量化不同的影响成为可能。

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.