
*** Unfolding the early fatigue damage process for CFRP cross-ply laminates ***

Authors: Xi Li, Julian Kupski, Sofia Teixeira De Freitas, Rinze Benedictus, Dimitrios Zarouchas

Structural Integrity & Composites Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629HS, The Netherlands


Corresponding author: Dimitrios Zarouchas
 
Contact Information:

d.zarouchas@tudelft.nl

Office NB 0.45
Delft University of Technology - Faculty of Aerospace Engineering
2629 HS Delft
The Netherlands

***General Introduction***
This dataset is being made public both to act as supplementary data for publications and the PhD thesis of Xi Li and in order for other researchers to use 
this data in their own work.

The data in this data set was collected in the Structures and Materials Laboratory of the Delft University of Technology - Faculty of Aerospace Engineering, 
between June 2019 and September 2019.

***Purpose of the test campaign***
The purpose of these experiments was to unfold the damage accumulation process, understand the interaction between different damage mechanisms, and quantify
their contribution to stiffness degradation.

***Experimental setup***
The specimens used in the present work were fabricated using UD Prepreg named Hexply F6376C-HTS(12 K)-5-35%. This UD Prepreg system has a 
nominal ply thickness of 0.125 mm and a nominal fibre volume content of 58%.The laminated panels of 300 mm 300 mm size and stacking sequence of [02/904]S 
were cured inside an autoclave according to recommendation from Hexcel. Based on ASTM D3479/D3479M-19 standard, the cured panels were cut into rectangular
shape with 250 mm  25 mm size using a water-cooled diamond saw and both ends of specimens with 50 mm length were glued with thick paper tabs using 
cyanoacrylate adhesive to increase clamping grip.

Seven specimens were tested under tensiontension fatigue loading on a 60 kN hydraulic fatigue machine at room temperature. Constant amplitude of sinusoidal 
waves, with maximum stress of 507 MPa (70% of UTS), stress ratio 0.1 and frequency 5 Hz were applied, while the tensile loading and unloading ramps were 
applied before and after every 500 cycles with the rate of 19 kN/s. The maximum stress was determined based on the results of static tensile and preliminary
fatigue tests. During tests, two 9 Megapixel cameras with 50 mm-focal-length lens were placed at left and right sides of the clamped specimens to monitor 
the damage on both edges. The edge surfaces of each specimen were covered with thin white paint in order to enhance the white-black contrast of cracked and 
uncracked regions. Furthermore, the exterior 0 ply was painted with a white base coat and printed with black dots using a speckle roller with the dot size of 
0.18 mm. A second pair of 5 Megapixel cameras with 23 mm-focal-length lens was placed in the front of specimens to measure the in-plane strain field. All 
cameras were triggered simultaneously during the tensile loadingunloading ramps to capture images every 50 ms. Tests stopped when reaching 1e5 cycles, which
guarantees that the stiffness degradation develops through the Stage I and approaches to the stable phase of Stage II. Two specimens were scanned by an 
ultrasonic C-scanner to detect the delamination area after test.For DIC calculations, a subset size of 29 pixels and step size of 7 pixels were fixed for all 
specimens. The interest area was fixed at gauge region with ~ 80 mm length for both edge damage and DIC.

***Description of the data in this data set***
The data included in this dataset has been organised to separate xls-files based on the figures in the related publication.
