Flaw and damage assessment in torsionally loaded CFRP cylinders using experimental and numerical methods

Abstract

Flaw and damage assessment in torsionally loaded CFRP cylinders using experimental and numerical methods, Composite Structures (2015), doi: http://dx.doi.org/10. 1016/j.compstruct.2015.05.025 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractCFRP structural elements are prone to failure initiating from defects. While defects are expected after damage has occurred, flaws and voids can already be present after manufacturing. To study the criticality of such defects CFRP cylinders have been manufactured from a lay-up that was designed to predict damage mode and to allow for controlled damage growth under torsional load. FEA simulations of defect-free and flawed cylinder models were performed to first ply / interface failure. X-ray Computed Tomography revealed that cylinders manufactured with different finishing had a completely different void content and distribution. Simulations of failure, using finite element models, for the two classes of void distribution are corroborated by experimental results for the ultimate load, and damage initiation from manufacturing flaws is confirmed. Digital Speckle Pattern Interferometry was used to identify flaws using thermal and mechanical loading, while infrared thermography and thermoelastic stress analysis were used to identify possible failure initiation sites and monitor the failure process and damage growth, whilst the specimen was loaded in torsion.

Towards Automated Tracking of Initiation and Propagation of Cracks in Aluminium Alloy Coupons Using Thermoelastic Stress Analysis

“…TSA maps the surface stresses in a material based on small temperature variations measured by an infrared (IR) detector while the material is dynamically loaded [5,9]. Cracks or damage can therefore be located due to the indicative stresses present, which has been exploited previously in a range of studies [10][11][12][13][14][15]. The position of the crack is often determined from the phase profile along the line of the crack, which requires knowledge of the crack location and orientation [10][11][12].…”

Modal-based vibrothermography using feature extraction with application to composite materials

“…Apart from vibrothermography which relies on vibration, there are other similar damage detection principles based on IRT, such as thermoelastic stress analysis that measures the temperature change due to deformations caused by quasi-static or low-frequency elastic cyclic stresses. [15][16][17][18] However, to the authors' knowledge, there has been limited research that combines modal testing, vibrothermography, and feature extraction, which are the three components sequentially demonstrating the capability of determining the damage detection. Compared to past research outcomes focusing mainly on the processing of data from IRT inspections, the main novelty of this research is the inclusion of vibrothermography, which covers the detailed procedures on the execution of vibrothermographic inspections.…”

“…Apart from vibrothermography which relies on vibration, there are other similar damage detection principles based on IRT, such as thermoelastic stress analysis that measures the temperature change due to deformations caused by quasi-static or low-frequency elastic cyclic stresses. 15–18…”