The cooling conditions used in the forming process of composite materials play an important role in the creation ofresidual stress. In this study, a new method for measuring residual stress in composite laminates is presented. Three cooling conditions were used to produce different residual stress levels. Residual stresses in [02/902]s and [08] laminate have been measured by the incremental holedrilling method combined with 3-D finite element modelling. A software which quickly calculates all the coefficients for each increment was developed. The automatic procedure can be used to calculate the calibration coefficient for any type oflaminate (ply number, mechanic characteristics,...) and whatever the number of increments and their depths. The different results show that this method provides access to the in-depth distribution and through thickness ofresidual stress in the laminate with a good accuracy and practicality.
Analysis of the stress state in a composite plate under torque loadings and some practical information are necessary for the engineering design. The large rotation displacement has been taken into account for the stress analysis and the experimental results have shown a good agreement with the analytical results. It is found that the normal stress due to the fiber deformation is no longer negligible if the rotation angle becomes important and we notice also that there exists a compression zone in the middle of the plate and two tension zones in each side, the ratio of the compression zone width to the total width is about 0.58. The maximum tension stress in the plate is double its compression stress. The experimental observations have shown that the shear stresses 712max and jT13m seem responsible for the material degradation under torque loadings, and the determination of these shear stresses has to use the effective torque (MAff) instead of the applied torque (M.).
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