Guided waves inspecting composite materials for internal damage.

Impact Damage in Composites: Can Guided Waves and Artificial Models Lead to Safer Structures?

Lena Kashyap in Tech & Innovation July 2025 • 4 min read.

"New research explores how guided wave-based inspection and experimental models can improve the detection of impact damage in composite materials, paving the way for enhanced structural health monitoring in aerospace and other industries."

Composite materials are increasingly used in various industries due to their high strength and stiffness-to-weight ratios. However, their susceptibility to hidden damage remains a significant concern. Traditional Non-Destructive Testing (NDT) methods, while mature, are often time-consuming and conducted at scheduled intervals, limiting real-time assessment of structural integrity. This is where Structural Health Monitoring (SHM) comes in, offering a continuous and improved approach to evaluating structural health.

SHM promises higher safety standards through automated systems that minimize human interaction during inspections. Studies have shown that effective SHM methods can reduce maintenance costs for aircraft fleets by over 30%. For example, extending the life of the Canadian Air Force's F-18 fleet by monitoring operational loads can save hundreds of millions of dollars. With the rising maintenance costs of aging aircraft estimated at over $10.4 billion worldwide annually, SHM is a crucial area of interest for the aerospace community.

Among the various SHM techniques, guided wave-based strategies stand out for their cost-effectiveness, speed, repeatability, and sensitivity to small damages. These strategies can inspect large structures and detect both surface and internal damage, making them a promising solution for ensuring the safety and reliability of composite structures.

How Can Guided Waves Help?

Guided waves inspecting composite materials for internal damage.

Guided wave techniques utilize piezoelectric transducers to generate waves that propagate through the material. These waves interact with any inhomogeneities, such as structural features or defects, and the resulting echoes provide valuable information about the material's condition. Damage significantly influences wave propagation, causing scattering effects like reflection, transmission, and mode conversion. This forms the basis for elastic wave-based damage identification, as different locations and severities of damage create unique scattering phenomena.

Ultrasonic guided wave propagation with piezoelectric transducers has been proposed for effective inspection of composite structures and repaired composites, as well as bonded joints. For instance, when a symmetric mode (SO) encounters a delamination, it generates a new shear horizontal (SH0) mode, in addition to transmitted and reflected SO waves. By analyzing the amplitude ratio of reflected waves and the arrival time, the delamination length can be quantitatively evaluated.

Surface and Internal Damage Detection: Detects defects not visible externally.
Piezoelectric Transducers: Generates and measures wave signatures.
Wave Scattering Analysis: Assesses reflection, transmission, and mode conversion.

Researchers are exploring how to simulate damage using artificial methods, such as inserting Teflon tapes during manufacturing. These methods are common for calibrating sensitivity in NDT but require validation for low-order guided waves. Current SHM approaches often use the A0 mode below 300 kHz for efficient interlaminar delamination detection in CFRP. However, many studies are limited to 2D considerations, leaving a gap in understanding 3D scattering behavior. Factors like hole diameter, wavelength aspect ratios, and stacking sequences also influence wave scattering characteristics, necessitating further investigation.

Toward Safer Composite Structures

The research concludes that mid-plane artificial delamination and impact damage exhibit distinct diffraction patterns, while non-mid-plane artificial delamination and low energy impact damage show similar directivity patterns. The reflection increases with frequency for both Teflon-type artificial delamination and real impact damage, whereas transmission decreases with increasing frequency. The study's findings offer valuable insights for designing effective SHM systems. Further research will focus on optimizing artificial damage models using Teflon tape to mimic realistic damage scenarios and improve guided wave scattering analysis.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1115/1.4040719, Alternate LINK

Title: Experimental Model Of Impact Damage For Guided Wave-Based Inspection Of Composites

Subject: Mechanics of Materials

Journal: Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems

Publisher: ASME International

Authors: Mohammad H. Sherafat, Nicolas Quaegebeur, Pascal Hubert, Larry Lessard, Patrice Masson

Published: 2018-08-16

Everything You Need To Know

Why are composite materials increasingly used despite the concern for hidden damage?

Composite materials are increasingly used in various industries because of their high strength and stiffness-to-weight ratios. However, they are susceptible to hidden damage, making methods like Structural Health Monitoring (SHM) crucial. While traditional Non-Destructive Testing (NDT) methods exist, they are often time-consuming and conducted at scheduled intervals, limiting real-time assessment. SHM offers a continuous approach to evaluating structural health, addressing the limitations of traditional methods but requires advancements in techniques like guided wave analysis and damage modeling to ensure comprehensive damage detection.

How do guided wave techniques detect damage in composite structures, and what are the key components involved?

Guided wave techniques use piezoelectric transducers to generate waves that propagate through the composite material. These waves interact with any inhomogeneities, such as structural features or defects, causing scattering effects like reflection, transmission, and mode conversion. By analyzing these interactions, particularly the amplitude ratio of reflected waves and their arrival time, it's possible to identify and quantitatively evaluate damage, such as delamination length. This method allows for the detection of both surface and internal damage that may not be visible externally. The effectiveness of guided wave techniques depends on the ability to accurately interpret the wave signatures generated by the piezoelectric transducers and analyze the resulting scattering patterns. Factors like the frequency of the waves and the properties of the composite material also play a significant role.

What are the cost-saving benefits of implementing Structural Health Monitoring (SHM) in industries like aerospace?

Effective Structural Health Monitoring (SHM) methods can significantly reduce maintenance costs, with studies showing potential savings of over 30% for aircraft fleets. For example, monitoring operational loads can extend the life of aircraft, potentially saving hundreds of millions of dollars. SHM provides continuous assessment, reducing the need for frequent manual inspections. The aerospace community is particularly interested in SHM because the rising maintenance costs of aging aircraft are high. SHM can lower costs by optimizing maintenance schedules, detecting damage early, and minimizing downtime for repairs.

What are artificial damage models, such as Teflon tape inserts, and how are they used in the context of guided wave analysis for composite structures?

Artificial damage models, like inserting Teflon tapes during manufacturing, are used to simulate damage in composite materials. These models are common for calibrating sensitivity in Non-Destructive Testing (NDT). In guided wave analysis, these artificial damages help researchers understand how waves interact with different types and sizes of defects. For example, researchers are exploring how mid-plane artificial delamination and impact damage exhibit distinct diffraction patterns, while non-mid-plane artificial delamination and low energy impact damage show similar directivity patterns. These models provide a controlled way to study wave scattering characteristics and validate the effectiveness of guided wave techniques in detecting and characterizing damage. Optimizing these models using materials like Teflon tape is crucial for mimicking realistic damage scenarios and improving the accuracy of SHM systems.

What are the limitations of current Structural Health Monitoring (SHM) approaches using guided waves, and what future research directions are being explored to address these limitations?

Current Structural Health Monitoring (SHM) approaches using guided waves often focus on the A0 mode below 300 kHz for detecting interlaminar delamination in CFRP, but many studies are limited to 2D considerations. This leaves a gap in understanding 3D scattering behavior, which is essential for accurately characterizing complex damage scenarios. Factors like hole diameter, wavelength aspect ratios, and stacking sequences also influence wave scattering characteristics. Future research will focus on optimizing artificial damage models using Teflon tape to mimic realistic damage scenarios and improve guided wave scattering analysis. The goal is to develop more comprehensive SHM systems that can accurately detect and characterize damage in composite structures.