Study of quantification methods in self-healing ceramics, polymers and concrete – a route towards commercialisation

During the past decades, research in self-healing materials has focused on the improvement in mechanical properties, making stronger materials, able to bear increasing solicitations. This strategy proved to be costly and in some cases inefficient, since materials continue to fail, and maintenance costs remained high. Instead of preparing stronger materials, it is more efficient to prepare them to heal themselves, reducing repairing costs and prolonging their lifetime. Several different self-healing strategies, applied to different material classes, have been comprehensively studied. When new materials are subject of research, the attention is directed into the formulations, product processing and scale-up possibilities. Efforts to measure self-healing properties have been conducted considering the specific characteristics of each material class. The development of comprehensive service conditions allowing an unified discussion across different materials classes and the standardization of the underlying quantification methods has not been a priority so far. Until recently, the quantification of self-healing ability or efficiency was focused mostly on the macroscale evaluation, while micro and nanoscale events, responsible for the first stage in material failure, received minor attention. This work reviews the main evaluation methods developed to assess self-healing and intends to establish a route for fundamental understanding of the healing phenomena

Investigation of push-out delamination using cohesive zone modelling and acoustic emission technique

Push-out delamination is a serious concern in the drilling of fibre-reinforced composite materials. This damage occurs as the drill reaches the exit side of the material and can reduce the strength and stiffness of the structure. In this paper, a three-point bending test is performed on glass/epoxy-laminated composites to simulate the push-out delamination induced by thrust force during drilling. Cohesive zone modelling and acoustic emission monitoring are utilized to investigate the push-out delamination. Initially, double cantilever beam and end-notched flexure tests were performed to calibrate the cohesive zone modelling model. Following that, the actual loading condition is simulated using cohesive zone modelling-based finite element modelling. Energy of the acoustic emission signals is also used to detect the initiation of the delamination. The results obtained from cohesive zone modelling and acoustic emission showed that the applied methods can be used to understand and predict the initiation of push-out delamination and its progression. Finally, it is concluded that the proposed cohesive zone modelling and acoustic emission techniques can be used in the design stage as well as during the drilling process of laminated composite structures to avoid delamination

Experimental study of temperature effect on the mechanical properties of GFRP and FML interface

Interface between laminates has always been the weakest part of bonded materials which is prone to delamination. This is even more prevalent in bonding of two different materials. The research aims to evaluate delamination of dissimilar materials under a range of temperature. This is a part of the experimental study to investigate the potential of fiber metal laminates (FML) to be used in high temperature environment. The mechanical response of interface of hybrid laminate was characterized at temperatures ranging from 30 to 110 °C. Double cantilevered beam (DCB) and end notched flexure (ENF) tests were conducted on glass fiber laminated aluminum specimens to obtain Mode-I and Mode-II delamination properties with use of data reduction. Mode-I fracture toughness (GIC) is significantly degraded by 59.45% at 70 °C and up to 83.65% at 110 °C. Mode-II fracture toughness (GIIC) only slightly degrades by 10.91% at 70 °C but drops rapidly by 82.84% at 110 °C