Markus Zogg

An experimental comparative study on non-conventional surface and interface damping techniques for automotive panel structures

In order to increase the comfort of vehicle drivers, automotive panel structures are normally damped on their surfaces. Common surface damping treatments like free layer damping or constrained layer damping have the drawback of heavy weight and temperature as well as frequency dependent damping performance. New alternatives with simple structure, high robustness and light weight are sought. In this contribution, three different passive and active damping approaches were investigated: interface damping (ID), active constrained layer damping (ACLD) and particle damping (PD). They were surveyed under same boundary conditions and their performances were compared in terms of weight. The results show that ID strongly decouples the vibration from the source to the panel and provides steady performance over the whole frequency range. ACLD is a lightweight treatment with high damping capability for special mode shapes. PD is an effective simple damper providing excellent damping performance.

Simulation of the cure of paste adhesives by induction heating

This study, part of the European JTI ‘Clean sky’, presents a simulation model designed to predict the evolution of the degree of cure of the paste adhesives used in carbon fiber reinforced polymer bonded systems cured by induction heating. The simulation combines induced Eddy currents in electrical conductive materials, which cause the heating of the carbon fiber reinforced polymer adherents by Joule effect, and the consequent chemical reaction which gives the relation between temperature, time and degree of cure of the adhesive. The model is validated and used to analyze the impact of different parameters on the degree of cure of the paste adhesive.

Additive Manufacturing of Structural Cores and Washout Tooling for Autoclave Curing of Hybrid Composite Structures

This paper presents a study combining additive manufactured (AM) elements with carbon fiber-reinforced polymers (CFRP) for the autoclave curing of complex-shaped, lightweight structures. Two approaches were developed: First, structural cores were produced with AM, over-laminated with CFRP, and co-cured in the autoclave. Second, a functional hull is produced with AM, filled with a temperature- and pressure-resistant material, and over-laminated with CFRP. After curing, the filler-material is removed to obtain a hollow lightweight structure. The approaches were applied to hat stiffeners, which were modeled, fabricated, and tested in three-point bending. Results show weight savings by up to 5% compared to a foam core reference. Moreover, the AM element contributes to the mechanical performance of the hat stiffener, which is highlighted by an increase in the specific bending stiffness and the first failure load by up to 18% and 310%. Results indicate that the approaches are appropriate for composite structures with complex geometries.

Modeling of void formation during the curing process of paste adhesives

In this study, the void formation of the paste adhesives used for bonding of aerospace components is investigated. When high temperatures are applied to accelerate the curing process, volatiles evaporate; therefore the mechanical performance of joints is affected as a result of an increased void content. Today, mass reduction models only consider the degradation of fully cured samples, not taking into account the influence of the curing process on the quality of the paste adhesive. The fundamental idea of this paper is that the amount of mass reduction as a result of evaporation of the paste adhesive decreases with higher curing progression. For quantification, a model is defined approximating the mass reduction in a paste adhesive as a function of temperature, time and the degree of cure. Thermo gravimetric analysis is used to obtain the experimental data of the evaporation process for curing cycles with a single dwell at different temperatures applied to the paste adhesive. These data are used to define a theoretical model, which is validated by comparing the experimental and simulated data for non-isothermal heating processes. Finally, a relation between evaporated mass and void generation during the curing process is established in order to assess the bonding quality of the joint in terms of final void content as a result of the curing cycle.

Multifunctional Composite Structures With Integrated Damping Treatments: A Parametric Study

A parametric study on composite laminate plates with integrated damping treatment is realized. The goal is to assess the impact of a viscoelastic core on the mechanical performances as well as on the vibration damping efficiency. This work considers as design parameters the damping layer thickness and its position in the laminate lay-up. The obtained results enable to propose a guideline for multifunctional composite structure with intergrated damping treatment.© 2010 ASME