Search

The influence of anisotropic thermal diffusivities on non-destructive testing of CFRP laminates using pulse phase thermography (PPT) was studied analytically. The results show that the optimum frequency for maximizing detectable depths of defects increases concomitantly with the increase in the ratio of the thermal diffusivities in the through-thickness direction to that in the in-plane direction. Furthermore, the phase difference between sound and defective areas decreases significantly with decreased. These predicted tendencies were verified through experiments. Experimental results also demonstrated that defects of 10 mm in diameter can be detected up to around 5 mm depth in CFRP with lowerbut only to around 1 mm in CFRP with higher [ABSTRACT FROM PUBLISHER]

Abstract: This paper discusses the accuracy of ply angle alignment and how it relates to out-of-plane deformation in carbon fiber reinforced plastics (CFRP) laminates. We investigated the deformation of symmetrical cross-ply laminates under hot and humid conditions. In spite of the symmetrically stacked laminates, unpredictable out-of-plane deformation occurred over time due to ply angle misalignment. The deformation was unstable and disproportionate to the absorbed moisture. A Monte Carlo simulation based on laminate theory was performed to quantify the deformation induced by the ply angle misalignment. Symmetrical cross-ply laminates were found to twist as they absorbed water when they underwent ply angle misalignments. By comparing the analytical results with experimental results, we concluded that a standard deviation of approximately 0.4° exists as ply angle misalignment in the laminates used in this study and that this slight ply angle misalignment can be a significant factor in out-of-plane deformation of cross-ply laminates. [Copyright &y& Elsevier]