Composite Laminate Delamination Detection Using Transient Thermal Conduction Profiles and Machine Learning Based Data Analysis

Abstract

Delaminations within aerospace composites are of particular concern, presenting within composite laminate structures without visible surface indications. Transmission based thermography techniques using contact temperature sensors and surface mounted heat sources are able to detect reductions in thermal conductivity and in turn impact damage and large disbonds can be detected. However delaminations between Carbon Fibre Reinforced Polymer (CFRP) plies are not immediately discoverable using the technique. The use of transient thermal conduction profiles induced from zonal heating of a CFRP laminate to ascertain inter-laminate differences has been demonstrated and the paper builds on this method further by investigating the impact of inter laminate inclusions, in the form of delaminations, to the transient thermal conduction profile of multi-ply bi-axial CFRP laminates. Results demonstrate that as the distance between centre of the heat source and delamination increase, whilst maintaining the delamination within the heated area, the resultant transient thermal conduction profile is measurably different to that of a homogeneous region at the same distance. The method utilises a supervised Support Vector Classification (SVC) algorithm to detect delaminations using temperature data from either the edge of the defect or the centre during a 140 s ramped heating period to 80 °C. An F1 score in the classification of delaminations or no delamination at an overall accuracy of over 99% in both training and with test data separate from the training process has been achieved using data points effected by transient thermal conduction due to structural dissipation at 56.25 mm.

Delamination Localization in the Composite Thin Plates Using Ensemble Learning: Bagging and Boosting Techniques

“…They employed six natural frequencies to predict the location and area of 400 delaminations. Gillespie et al [25] used transient thermal conduction pro les for delamination detection using support vector classi cation. They evaluated an F 1 score with 99% accuracy.…”

Adaptive Fiber-Ring Lasers Based on Isopropanol Filled Microfiber Coupler for High-Sensitivity Temperature Sensing

“…Among them, temperature, as the most important parameter for perceiving the external environment, has received the most extensive attention from scientists, and has been widely researched [ 11 , 12 , 13 ]. Various optical fiber structures have been designed to improve the sensitivity, stability, and practicability of temperature sensing [ 14 , 15 , 16 ]. Common structures include Mach Zehnder Interferometer (MZI), Fabry Perot Interferometer (FPI), Sagnac Ring, and Fiber Bragg Grating (FBG) [ 17 , 18 , 19 , 20 ].…”