Interfacial Failure in Stitched Foam Sandwich Composites.

Yue Hu,Jihui Wang,Yibo Wu,Jun Zhu

doi:10.3390/ma14092275

Yue Hu, Jihui Wang + Show 2 more

Open Access

https://doi.org/10.3390/ma14092275

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Abstract

In this paper, the use of a customized automatic reinforcement stitching equipment was demonstrated. The stitching of foam sandwich composite preforms was achieved to obtain structures with improved interfacial properties. The effect of different stitching spacings on the crack propagation process in glass fiber reinforced plastics (GFRP)/foam sandwich composite interfaces was examined by Mode-I Cracked Sandwich Beam (CSB) fracture tests. The load–displacement curve, the crack propagation process, and the release rate of critical strain energy were analyzed. The CSB fracture test results show that the stitching treatment with different stitching spacings increase the peak load and fracture displacement. Furthermore, it was found that the mechanism of crack propagation is changed by the stitching process. The release rates of the critical strain energy in specimens with 0- and 10-mm stitch spacings were evenly distributed, with an average of 0.961 kJ/m2 and 1.667 kJ/m2, respectively, while the release rates of critical strain energy in specimens with 6-mm and 8-mm stitch spacings were linearly distributed. The CSB fracture tests confirmed that the best suture spacing was 8 mm. Based on these results, the mechanism of crack propagation and the toughening mechanism of the resin column could be revealed.

Highlights

The specimen loading process could be divided into three stages: linear increase of the load (I), crack initiation (II), and crack propagation (III) [25]: in the linear increasing stage (I), the load–displacement curves of all specimens were approximately linear before the initial crack initiation, when the prefabricated cracks started opening
This result in cracks propagating along the interface in FH-6, FH-8 and FH-10 specimens, which suggested that the suture treatment had changed the crack propagation mechanism of the foam sandwich structures to a certain extent
Foam sandwich structures were sutured by a customized automatic reinforcement stitching equipment and the Cracked Sandwich Beam (CSB) test specimens were prepared

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Yudhanto et al [13,14] investigated the damage characteristics of 3D stitched composites in in-plane tension and compression with different stitching parameters by tensile and compression tests, where the results showed that the stitching treatment could effectively increase the tensile strength of composites and reduce the compressive strength of laminates This could be related to the suppression of edge delamination and in-plane fiber bending. Francesconi et al [18] conducted a low-velocity impact test on stitched laminates using the finite element method and investigated the in-plane and interlaminar damage processes and the inhibitory effect of sutures on delamination. The preparation process of specimens for CSB fracture tests is described and the results of such CSB fracture tests are presented. (3) The test results are analyzed from three aspects: (i) load–displacement curves, (ii) crack propagation process and (iii) strain energy release rate. (4) A summary and a discussion of the research findings presented in this work

Raw Materials

Load–Displacement Curves

Crack Propagation Process

Release Rate of Critical Strain Energy

Conclusions