Analysis and Performance of Composites

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

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**Chapter 9**

**Abstract**

Damage Identification and

Assessment Using Lamb Wave

A methodology for identify damage in the fiber reinforced polymer (FRP) composite has been proposed in this article. The Lamb wave dispersion theory was used to find the fitted peak frequency and loss less finite element model was used to find the modal frequencies in the composite laminates. The change in modal parameters with respect to undamaged and damaged specimen has been considered for the structural diagnosis. The combined finite element and Lamb wave method has been used to obtain damping parameters. The damping capacity was calculated at higher frequency and smaller amplitudes by using hybrid method. The Lamb waves were generated using ultrasonic pulse generator setup. The proposed method

was implemented on FRP laminates (CFRP and GFRP) and the results were

Composite materials with advanced properties like, high specific strength and fatigue resistance are being used for many components of aircraft structures in recent era. However, they have high chances of failure when they are subjected to low velocity-impact, which could lead to barely visible impact damage (BVID). BVID are considered to be internal defects which can lead to catastrophic accidents in service. Damage is defined as the changes introduced into a system that leads to affect adversely to its current or future performance. Damage assessment techniques in the structural dynamics have been divided into three categories such as linear, non-linear and transient vibrational measurements. The change in modal parameters such as natural frequencies and material damping can be considered as the prevalent damage detection methods in structural assessment procedure. The existing damage in a structure, leads to the reduction in stiffness and consequently

**Keywords:** carbon fibers, Lamb wave, glass fibers, vibration, damping,

Propagation Parameters and

Material Damping in FRP

Composite Laminates

*Beera Satish Ben and Beera Avinash Ben*

compared with bandwidth method.

decreasing of the natural frequencies of the system.

acoustic emission

**1. Introduction**

**151**
