HyCEML - Hybrid CFRP / elastomer / metal laminates with elastomer layers for targeted adjustment of damping behavior

  • Contact:

    M.Sc. Alexander Jackstadt

  • Funding:

    DFG - Deutsche Forschungsgemeinschaft

  • Partner:

    Institute for Applied Materials - Materials Science and Engineering - Hybrid and Lightweight Materials

The main objective of the project is to identify and to investigate the advantages and disadvantages of hybrid laminates made of carbon fiber reinforced polymers (CFRP), elastomers and metals (HyCEML) in terms of its calm, smooth and smart behavior. In contrary to conventional fiber-metal laminates, the elastomer forms the interface between metal and CFRP and establishes the generally very good damping (calm) behavior of HyCEML. Beyond damping, the elastomer covers a series of further (smart) aspects that are crucial in hybrid systems. It acts as adhesive and thus facilitates the joining of the dissimilar materials. It compensates internal stresses caused by a mismatch of the coefficients of thermal expansion (CTE mismatch) and acts as an insulating layer that counteracts contact corrosion. Furthermore, it improves the impact tolerance of the hybrid laminate significantly due to energy absorption in the elastomer layer in combination with superior delamination resistance. A jerk-free (smooth) operation of the system can be assured. Therefore, comprehensive experimental and numerical investigations are needed, which require new methods or method adjustments. Since the damping characteristics of the hybrid laminate are highly anisotropic, one of the objectives of this project is the experimental characterization of the anisotropic behavior as well as their underlying mechanisms. In addition to anisotropy, investigating the calm properties aims for the analysis of the laminates damping characteristics. In addition to the characterization of the calm properties, a further objective represents the analysis of smart aspects such as the compensation of the CTE mismatch and the corrosion behavior. Based on the experimental results, suitable finite element (FE) modeling techniques need to be developed to describe the laminate damping behavior numerically. The first modelling objective is to build up and validate detailed multi-layer FE models to be used to investigate the effect of varying layup and loading constitutions on the damping behavior. For verification and validation purposes, analytical closed-form solutions (e.g. for simply supported plates) and experimental tests are needed. Furthermore, specific laminate configurations need to be investigated to deliberately increase the damping capability of the laminate. Since multi-layer shell elements are computationally more efficient than detailed multi-layer FE models, a suitable shell theory is needed to model the hybrid laminates on structural level. Based on the state of the art in multi-layer modelling and based on the experimental results to be obtained, an essential objective of the proposed project is the development of a multi-layer shell formulation. A further aim of the project is to investigate the influence of different geometric aspects onto the resulting damping behavior of the structure. To do this, different generic parts with varying geometrical complexity will be modelled.

 

 

DFG-priority programme 1897 calm, smooth, smart: HyCEML - Hybrid CFRP / elastomer / metal laminates with elastomer layers for targeted adjustment of damping behavior

Motivation

Lightweight design is used to increase efficiency in all kinds of vehicles. Although common lightweight materials offer a high specific stiffness at a low mass, monolithic materials rarely fulfill all requirements. A composite laminate made from layers of CFRP, elastomer and metal for example enables the specific adjustment of the damping capabilities of lightweight structures, which are usually prone to strong vibrations. This material is based on common fiber metal laminates:

CFK/Metall-Laminate:

  • High energy absorption under impact loading
  • Susceptible to corrosion

Elastomere Zwischenschicht:

  • Adjustment of the damping behavior
  • Compensation of thermal residual stresses
  • Prevention of galvanic corrosion
  • Replaces adhesive

 

Scientific goals

This project’s main objective is the scale bridging experimental and numerical analysis of the dynamics, such as damping and natural frequencies to name a few, of HyCEML. The two project partners FAST and IAM-WK pursue the following goals:

  • Experimental characterization of the Mullins effect in the hybrid laminates and its constitutive modeling with suitable material models
  • Identification of damage mechanisms occurring under low-velocity impact in HyCEML
  • Consideration of these damage mechanisms in fine-element models for the efficient analysis of damaged components
  • Identification of different damage mechanisms’ influence on the dynamic behavior of HyCMEL
  • Deduction of guidelines for the damage tolerant design of well damped laminates

 

Methods
  • Intrinsic manufacturing process of laminates in press process
  • Quasi-static characterization of constituents and hybrid laminates
  • Dynamic-mechanical-analysis and modal analysis
  • Closed-form analytical solutions for the rapid prediction of the vibrational behavior of hybrid laminates
  • Complex material models depicting different kinds of damage mechanism within the laminate

 

 

Bild FAST-LBT
Figure 1: Demonstrator components manufactured in different lamination schemes.
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Figure 2: Simulation of a vibrating demonstrator component.
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Figure 3: Mullins effect observed in the elastomeric damping layers used in the hybrid laminates.
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Figure 4: Impact test on HyCEML.

SPP 1897 - Calm, Smooth and Smart