The present review aims at gathering the available literature on damping in composite materials. A chronological review of test methods for damping estimation is presented in order to describe the time-line of the theoretical knowledge development in this field. In the last years many new material configurations have emerged that deserve investigation, such as nano-composites, hybrid laminates and sandwich materials. Damping models specifically meant for non-homogeneous materials are reported to provide a background for understanding this problem. Although not widely exploited yet, fibre reinforced polymers has the potential to be tailored for damping by acting on constituents, geometry and boundary conditions. Nano-composites, for instance, are shown to possess a high potential for damping purposes. New hybrid and sandwich-type structures are emerging as noise and vibration control solutions in lightweight applications. The effort devoted to mathematical and numerical model in view of Finite Element integration of damping properties is also addressed. Finally, the conclusions summarise the ideas of the authors on needed steps to advance the state-of-the-art in each of the described topic.

Damping in composite materials: Properties and models

An overview of the polymer-to-metal direct-adhesion hybrid technologies for load-bearing automotive components

An experimental nondestructive vibration-based technique for locating a delamination in a composite beam is presented. The method operates on the fundamental displacement eigenvector, which is converted to a curvature mode shape. The application of a unique, gapped smoothing damage detection method to the curvature yields a damage index that locates the delamination, irrespective of its position along the beam or depth within the beam. The procedure can operate solely on data obtained from the damaged structure. Models or data from the undamaged structure are specifically not required or used during the analysis. The procedure reported here is highly satisfactory for experimental data, where small variations in the measurement cause false features in other published curvature-based damage detection methods. The damage location method is demonstrated with a finite element model of a composite beam, where a delamination is modeled by relaxing connectivity between elements at the desired location of the delamination. The results of an experimental investigation of a composite beam with a manufactured delamination are also presented. When the gapped smoothing method was used on the experimental modal data, the delamination was successfully located.

Vibration Technique for Locating Delamination in a Composite Beam

Self-sensing is valuable for structural materials, especially those for smart structures. It does not involve the use of embedded or attached sensors, as the structural material is itself the sensor. Self-sensing was attained in carbon-fiber–polymer-matrix structural composites by using the interlaminar interface (i.e., the interface between the laminae of continuous fibers) as a sensor. The attributes sensed were temperature, moisture, damage, and stress. In the case of temperature sensing, the interlaminar interface functioned as either a thermistor or a thermocouple junction. The thermocouple approach required the fibers in the contacting laminae to be dissimilar, whereas the thermistor approach did not. By using two crossply laminae, a two-dimensional array of sensors was attained for spatial distribution sensing.

http://iopscience.iop.org/article/10.1088/0964-1726/13/3/017/pdf

Self-sensing attained in carbon-fiber–polymer-matrix structural composites by using the interlaminar interface as a sensor

This study investigates the effect of damage on beams with fixed boundary conditions using Fourier analysis of mode shapes in the spatial domain. A finite element model is used to obtain the mode shapes of a damaged fixed-fixed beam, and the damaged mode shapes are expanded using a spatial Fourier series and the effect of damage on the harmonics is investigated. This approach contrasts with the typical time domain application of Fourier analysis for vibration problems. It is found that damage causes considerable change in the Fourier coefficients of the mode shapes, which are found to be sensitive to both damage size and location. Therefore, a damage index in the form of a vector of Fourier coefficients is formulated. A neural network is trained to detect the damage location and size using Fourier coefficients as input. Numerical studies show that damage detection using Fourier coefficients and neural networks has the capability to detect the location and damage size accurately. Finally, the performance of the method in the presence of noise is studied and it is found that the method performs satisfactorily in the presence of some noise in the data.

Kung Fu Young

Papers

Dynamics of graphite/epoxy composite under delamination fracture and environmental effects