A Point‐wise Approach to the Analysis of Complex Composite Structures Using Digital Image Correlation and Thermoelastic Stress Analysis

Abstract

A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis", Strain, 51, 2015, 311-323. DOI: 10.1111 A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis Abstract:Thermoelastic Stress Analysis (TSA) and Digital Image Correlation (DIC) are used to examine the stress and strain distributions around the geometric discontinuity in a composite double butt strap joint (DBSJ). A well-known major limitation in conducting analysis using TSA is that it provides a metric that is only related to the sum of the principal stresses and cannot provide the component stresses/strains. The stress metric is related to the thermoelastic response by a combination of material properties known as the thermoelastic constant (coefficient of thermal expansion divided by density and specific heat). The thermoelastic constant is usually obtained by a calibration process. For calibration purposes when using orthotropic materials it is necessary to obtain the thermoelastic constant in the principal material directions, as the principal stress directions for a general structure are unknown. Often it is assumed that the principal stress directions are coincident with the principal material directions. Clearly, this assumption is not valid in complex stress systems and therefore a means of obtaining the thermoelastic constants in the principal stress directions is required. Such a region is that in the neighbourhood of the discontinuities in a bonded lap joint. A methodology is presented which employs a point wise manipulation of the Crammond, G., Boyd, S.W. and Dulieu-Barton, J.M., "A point-wise approach to the analysis of complex composite structures using digital image correlation and thermoelastic stress analysis", Strain, 51, 2015, 311-323.

Application of Digital Image Correlation to Address Complex Motions in Thermoelastic Stress Analysis

“…The results are not presented as stresses since the thermoelastic constants for the orthotropic face sheet and core materials are required. As the focus of the work is development of the motion compensation routine it was considered unnecessary to embark on a laborious material characterisation exercise as described in [20]. The results were adjusted for tension and compression by multiplying the amplitude data (ΔT) by ±1 in accordance with the phase data.…”

Measurement of the Appearance and Growth of Tow Buckling Defect in the Frame of Complex Shape Manufacturing Process by Using Fringe Projection Technique

“…Non‐destructive evaluation (NDE) techniques have been employed to inspect and characterise composite structures . Various NDE methods, such as the optical techniques of holography, electronic speckle‐pattern interferometry, shearography and time‐domain moiré interferometry, are used for thermoplastic or thermoset composites and are described by a number of authors . These techniques provide wide‐area qualitative imagery in the in‐ and out‐of‐plane displacement at the surface of a structure.…”

Data-rich characterisation of damage propagation in composite materials

“…There have been a few publications where TSA and DIC have been combined [15,16] but not on data that has been captured together in a synchronised manner. In [15] white light images were captured separately and used to correct for the motion in the IR data to improve the accuracy of TSA.…”

“…In [15] white light images were captured separately and used to correct for the motion in the IR data to improve the accuracy of TSA. In [16] the failure mechanisms in an adhesively bonded joint were studied using single camera DIC and TSA. The DIC was conducted on images collected from quasi static tests and the IR data for the TSA was captured during a separate test using cyclic loading.…”