Abstract
To detect the presence of damage, many structural health monitoring techniques exploit the nonlinear features that typically affect the otherwise linear dynamic response of structural components with internal defects. One of them is the Scaling Subtraction Method (SSM), which evaluates nonlinear features of the response to a high-amplitude harmonic excitation by subtracting a scaled reference signal. Originally tested on granular materials, the SSM was shown to be effective for composite materials as well. However, the dependence of the technique efficiency on the testing frequency, usually selected among the natural frequencies of the system, may limit its application in practice. This paper investigates the feasibility of applying the SSM through a broadband impulsive excitation, which would avoid the need of a preliminary modal analysis and address the issue of the proper selection of the excitation frequency. A laminated composite beam was tested in intact and damaged conditions under both scaled harmonic excitations of different frequency and broadband impulsive signals of scaled amplitude. Two damage indicators working on the frequency domain were introduced. The results showed a good sensitivity of the SSM to the presence and level of impact damage in composite beams when applied through a broadband impulsive excitation.
Highlights
High strength to weight ratios, good fatigue performance and excellent environmental and corrosion resistance are some of the features that have resulted in laminated composites being increasingly used in primary structural applications in many transport, mechanical and civil engineering fields
A wide range of Structural Health Monitoring (SHM) techniques based on integrated sensors and optimized signal processing algorithms have been developed to assess the presence of impact damage in composite structures
Encouraged by the promising preliminary results found in [24], the present paper aims to carry out a more detailed investigation of the possibility of adopting broadband impulsive excitations and damage indicators based on the analysis of signal magnitudes at selected frequencies, to make the Scaling Subtraction Method (SSM) more effective for the detection of low-velocity impact damage in laminated composite materials
Summary
High strength to weight ratios, good fatigue performance and excellent environmental and corrosion resistance are some of the features that have resulted in laminated composites being increasingly used in primary structural applications in many transport, mechanical and civil engineering fields. Encouraged by the promising preliminary results found in [24], the present paper aims to carry out a more detailed investigation of the possibility of adopting broadband impulsive excitations and damage indicators based on the analysis of signal magnitudes at selected frequencies, to make the SSM more effective for the detection of low-velocity impact damage in laminated composite materials. For this purpose, two series of experimental tests have been conducted on a laminate composite beam, the first one carried out with pure harmonic excitations tuned in turn at three natural frequencies of the system and the second one performed with broadband impulsive inputs. The results obtained under impulsive and harmonic excitations are compared and discussed
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