Damage analysis and fracture toughness evaluation in a thin woven composite laminate under static tension using infrared thermography

Abstract

International audienceThis work deals with the issue of damage growth in thin woven composite laminates subjected to tensile loading. The conducted tensile tests were monitored on-line with an infrared camera, and tested specimens were analysed using Scanning Electron Microscopy (SEM). Combined with SEM micrographs, observation of heat source fields enabled us to assess the damage sequence. Transverse weft cracking was confirmed to be the main damage mode and fiber breakage was the final damage leading to failure. For cracks which induce little variation of specimen stiffness, the classic "Compliance method" could not be used to compute energy release rate. Hence, we present here a new procedure based on the estimation of heat source fields to calculate the energy release rate associated with transverse weft cracking. The results are then compared to those computed with a simple 3D inverse model of the heat diffusion problem and those presented in the literature

Scaling effect in notched composites: The Discrete Ply Model approach

“…Another means to compare numerical and experimental results is through the extent of fiber failure before brutal propagation. Lisle et al proved that infrared emissions gave accurate estimations of damage growth in thin woven composite laminates subjected to tensile loading [50]. This method was adapted to notched laminated composites under tension.…”

Damage detection in CFRP by coupling acoustic emission and infrared thermography

“…Following assumptions are assumed for the infrared image processing to obtain the heat source estimation: the temperature variation has no influence on the microstructure state, internal coupling sources are neglected, external heat does not depend on the time, coefficients ρ, C and conductivity tensor k (second order tensor) remain constant during the test and heat sources are assumed homogeneous through the thickness (low thickness compared to the length and width of the sample). Under these assumptions, the heat diffusion equation can be written as follows [9,10]:…”

“…Acquired thermal fields can thus reveal and localize overheating related to degradation mechanisms (see works on carbon-epoxy of [5,6,7] and on glass-epoxy of [8]). Since temperature may be affected by external exchanges and/or by heat diffusion inside the material itself, the dissipation sources represent even a more accurate indicator of damage [9,10].…”

Passive infrared thermography measurement of transverse cracking evolution in cross‐ply laminates

“…Some authors have also used passive infrared thermography to monitor the damage appearance and growth into composite materials. Battams and Dulieu‐Barton performed DIC and infrared thermography on the same surface of a [90,0] s laminate and have shown that transverse cracks can be observed with the two measurement techniques at intermediate strain rate (32 s −1 ).…”