In machining technologies for fibre reinforced polymers, remote laser cutting plays a special role as it can minimize the drawbacks of conventional laser cutting methods, in particular thermally induced damage such as charred edges and matrix evaporation. In this contribution, a thermal simulation model for the remote laser cutting process is presented. With the aim of a universally applicable model that works independently of the selected carbon fibres, matrix system, and fibre content, the effective thermal material parameters are calculated with a rule of mixture from the microscopic parameters for fibre, matrix, and process gas. The evaporation of matrix and fibre material is modelled with phase transitions. The moving laser spot is modelled with a Gaussian distribution as a heat input on the upper side. The emerging process gas is assumed to absorb a part of the laser power according to the Lambert‐Beer law.

In this paper, an approach is presented that allows for a linkage between cutting process induced damage and the mechanical properties of the machined structures. For carbon fibre reinforced polymers, the milling and remote laser cutting processes are analysed. Open hole tensile test specimens, that are either milled or remote laser cut with three different cutting parameter configurations are tested. With a two-dimensional heat conduction simulation, the temperature field resulting from laser cutting is determined and thus the thermally induced damage is quantified. Those results are compared to micro-sections. The following structural analysis is based on an anisotropic damage model and is taking the thermal pre-damage into account. For this purpose two different thermal damage modelling approaches, based on damage variables and material parameter reduction, are compared. The influence of the cutting process on the structural properties is determined and compared with experimental results.

AbstractRemote laser cutting in carbon fibre reinforced polymers is a promising machining technology, which can reduce the main drawback in laser cutting, the heat affected zone. As the heat affected zone has a strong influence on the mechanical behaviour of the composite, an exact characterisation is a key challenge for the simulation and design of fibre reinforced polymers. In order to reach this goal, a laser cutting process model is introduced. Based on the finite difference method, the heat transport is modelled on a macroscopic scale. The macroscopic material parameters are calculated with a rule of mixture. Matrix and fibre evaporation, which cause the formation of the matrix evaporation zone and the gap, are modelled with phase transitions and an adaption in the rule of mixture.The simulation results are validated with micro‐sections of the cutting gap.

Remote laser beam cutting is a non-contact, tool-wear-free cutting technology that guarantees consistent cutting quality for fiber-reinforced polymers with high efficiency. Since it is a thermal process, a heat-affected zone (HAZ) inevitably occurs at the edge of the cut. Within this HAZ the original material condition is changed locally, which influences the mechanical behavior of the component. In this paper, we have investigated the effect of HAZ on fatigue behavior, for the first time, using a high-resolution X-ray Computed Tomography (XCT) for carbon fiber reinforced polymer (CFRP). The investigation methodology allows non-destructive diagnostics of the HAZ. The laser-cut materials were compared to those machined by conventional milling. The quantitative damage mechanisms, in terms of delaminations, transverse cracks, etc., were investigated and correlated to the laser and milled processes.

In this contribution a modelling approach for the laser cutting process simulation of carbon fibre reinforced polymers is introduced. The cutting process is modelled in a 3D thermal simulation, the material is modelled layer‐wise orthotropically. For the evaporation of matrix and fibre phase transitions are utilised. The laser spot is modelled with its gaussian distribution as a heat input on the upper side.

In this paper, an approach is presented that allows for a linkage between cutting process induced damage and the mechanical properties of the machined structures. For carbon fibre reinforced polymers, the milling and remote laser cutting processes are analysed. Open hole tensile test specimens, that are either milled or remote laser cut with three different cutting parameter configurations are tested. With a two-dimensional heat conduction simulation, the temperature field resulting from laser cutting is determined and thus the thermally induced damage is quantified. Those results are compared to micro-sections. The following structural analysis is based on an anisotropic damage model and is taking the thermal pre-damage into account. For this purpose two different thermal damage modelling approaches, based on damage variables and material parameter reduction, are compared. The influence of the cutting process on the structural properties is determined and compared with experimental results.

A new numerical model for wood-adhesive joints, which allows an efficient hygro-mechanical analysis of a glued joint by means of the finite element method, is proposed. A cohesive element model is modified by adding features to simulate the mechanical behaviour of and the moisture transport in the joint. The numerical investigations of two wood species, European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L.), are carried out based on experimental studies available in the literature. The simulated specimens contain a single bond line of animal adhesive, which is commonly found in historical wooden objects. Additionally, experimental investigations are also carried out in parallel to further validate the model. The results show that the numerical simulations are in agreement with the experimental results at mechanical loading. Under moisture loading, however, the numerical results are diverse in comparison to the experimental results. The reason for this difference is primarily due to the incomplete experimental data, which serve as input parameters for the numerical simulation.

AbstractRemote laser cutting in carbon fibre reinforce polymers is a promising machining technology which can reduce the main drawback in laser cutting, the heat affected zone. This contribution presents a two‐step modelling approach for the simulation of remote laser cut carbon fibre reinforce polymers, consisting of a damage model for the initially intact material and a model for the thermally damaged material.The static damage behaviour was modelled with the Pinho material model [1], which stands out due to its physically based failure criteria. Initial thermal damages caused by the heat input were modelled with the damage parameters of the Pinho model. The dimensions of the heat affected zone are taken from polished micro sections of the material around the cutting edge.As a numerical example, comparative tensile tests of milled and laser cut open hole specimens were simulated. The advantage of these specimens is the notch effect around the holes in the heat affected zone, which amplifies the differences between the two cutting technologies.