Experimental evaluation of the coefficients of thermal expansion in a composite laminate using digital image correlation

Abstract

A procedure for measuring simultaneously the coefficients of thermal expansion (CET) in the in-plane and the thickness directions in L-shaped composite laminated samples is presented. Measurements are carried out using digital image correlation, from which the displacements in one of the faces of the samples are measured when de sample undergoes a temperature increment inside an oven. From the in-plane displacement measurements, the in-plane strain tensor components and the corresponding CTE are determined. Results show that the presented technique is capable of determining these CTE with high accuracy. Displacement measurements in the direction normal to the face, enables determining the rotation of the face and consequently the difference between the CTE in the thickness direction and the CTE in the in-plane direction affected by the curvature. Results obtained for the CTE in the thickness direction show, first, values significantly higher than the CTE of the material in the in-plane direction normal to the fibres and, second, a high dispersion from one stacking sequence to another. These discrepancies were expected and are caused by the misalignment of the fibres in the corner zone of the samples.