Abstract
The aim of this research was to investigate the self-healing potential of damaged Al joints when bonded using novel eco-epoxide adhesives derived from tannic acid (TA). Two eco-epoxy components based on TA, (A) glycidyl ether and (B) glycidyl phosphate ester of TA, were produced. The effect of the eco-epoxy components on the self-healing ability was assessed in terms of the energy dissipation recovery after partial failure in a double cantilever beam (DCB) test, which was compared to the reference epoxy (R). The self-healing process required 2 h and 2 bars in an autoclave at 180 °C. Techniques such as DSC, FTIR and DMA showed residual activity and potential self-healing capability of the used adhesives. A combination of two monitoring techniques, Digital Image Correlation (DIC) and Acoustic Emission (AE), was used to monitor the strain distribution and damage propagation in the DCB specimens. The healing index for adhesives R, B and A was found to be 8.9%, 3.0%, and 82.5% respectively. The findings of this work highlighted the potential of using bio-based epoxy adhesives in structural adhesive bonding, as well as the prospect of utilizing their self-healing ability to restore the strength of such bonded parts.
Highlights
Polymers, nowadays, are commonly used in different industries such as transportation, electronics, stationery, sports equipment, and civil engineering [1]
As samples didn’t have previous thermal history, since they were cast, cured, and tested directly, Fig. 4 shows the Differential scanning calorimetry (DSC) results obtained in the two runs for all the tested adhesives R, A and B
Results from FTIR analysis showed the residual reactivity of the studied adhesives, where the highest was found for R and A, indicating the possible self-healing capability
Summary
Nowadays, are commonly used in different industries such as transportation, electronics, stationery, sports equipment, and civil engineering [1]. In the 1980s, the idea of self-healing polymeric materials was proposed to patch invisible microcracks and prolong the stability and service life of polymerized parts [2]. Self-healing polymer materials, in principle, have the potential to significantly recover their load transfer capability after being impaired. This type of recovery can occur naturally or as a result of the application of a particular treatment (such as radiation, heat, and water). As a result, these products are expected to greatly increase the reliability and protection of polymeric parts while mitigating the need for expensive active inspection or external servicing [3]. The self-healing mecha nism of bio-based polymers can be classified into two categories: i) the use of healing agents [8,9,10], and ii) intrinsic healing through the reversible chemical bonds [11,12,13]
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