Fatigue and damage analysis on aeronautical CFRP elements under tension and bending loads: Two cases of study

Abstract

The present work is focused on experimental monitoring procedures to investigate stresses and damage settlement during fatigue tests of CFRP elements under bending and tensile loads. Continuous damage accumulation, coupled with mechanical properties degradation are monitored with ultrasonic inspection and with thermographic full field analysis, during long lasting HC fatigue loads. Effects of localized bending loads and artificial composite wrinkle presence within a notch are source of delamination initiation, investigated two different types of specimens under fatigue. Combined monitoring approaches, based on thermo-elastic and dissipative phenomena, together with ultrasonic through thickness properties variations are claimed to offer precise damage state and localization during tests, subsequently aided by FEM damage model analysis in case of static failure zone identification, to be compared with experimental data; in addition, experimental DIC computation of deformation on specimen critical zones is performed in order to check failure and delamination initiation spot. The thermal parameters and experimental compliance correlation seem to indicate a similar signal variation during damage progress, verified also by contemporaneous ultrasonic inspections of some specimens in the failure zones of CFRP elements.