Assessment of Adhesion of Geopolymer and Varnished Coatings by the Pull-Off Method

This paper presents the results of testing the adhesion of geopolymer coatings and varnishes with ceramic additives to concrete and steel substrates. The measurement method used and described in this article was the pull-off method. The pull-off method test provides an easy way to evaluate the degree of adhesion of coatings to metal surfaces. The pull-off device provides values for the peel stress, which not only allows a quick determination of the adhesion of the coating to the substrate, but also makes it easier to compare the adhesion of several coatings to each other. However, this method requires appropriate preparation, so an attempt was made to determine its suitability for geopolymer layers. The results of testing the adhesion of a geopolymer layer to a geopolymer substrate and a concrete substrate are presented. As a result of this study, a higher adhesion strength of the geopolymer layer to the geopolymer substrate was found in comparison to geopolymer coatings applied on conventional concrete. Adhesion tests were also conducted for steel substrates to which both geopolymer and acrylic lacquer were applied.

Research on the key design and application of the device of opening cover and ring cutting and digging flesh of Mandari

Aiming at the problems of low efficiency and poor sanitation of manual cover opening and meat digging in the production of common orange tea, a multi station full-automatic meat digging machine for common orange tea is designed to realize the automatic cover opening and pulp separation device of green orange, so as to meet the production of common orange tea in Xinhui District of Jiangmen. The mechanism of peel stress and pulp separation damage of green citrus in the process of mechanical meat digging was studied. The state of peel contact deformation area of green Citrus under the extrusion of meat digging knife was analyzed by simulation, and the structural and operating parameters of de jacking and opening mechanism and meat digging mechanism were optimized. When the extrusion force was less than 35.6n, the peel damage rate could be minimized. Compared with manual operation, it reduces labor cost and production cost, saves processing time, and realizes automatic and rapid production.

Comparison of Tensile Strength and Fracture Toughness of Co-Bonded and Cold-Bonded Carbon Fiber Laminate-Aluminum Adhesive Joints

The purpose of this work is to compare the co-bonding vs. cold-bonding route on the adhesive joint performance of a CFRP (Carbon Fiber Reinforced Polymer) laminate–aluminum connection. In particular, the overlap shear, tensile strength and Mode I and Mode II fracture toughness will be evaluated. The adhesives for co-bonding and cold-bonding are, respectively, a thermosetting modified epoxy, unsupported structural film and a two-component epoxy adhesive, chosen as representative of applications in the high-performance/race car field. The emerging trend is that, in tensile e Mode I fracture tests, the failure path is predominantly in the composite. Mode II fracture tests instead resulted in a cohesive fracture, meaning that, under pure shear loading, the weakest link may not be the composite. The lap-shear tests are placed midway (cohesive failure for co-bonding and composite delamination for cold-bonding, respectively), probably due to the different peel stress values related to the different adhesive Young’s modulus. The exploitation of the full capacity of the adhesive joint, hence the possibility of highlighting better, different performances of co-bonding vs. cold-bonding, would require consistent improvement of the out-of-plane strength of the CFRP laminate and/or to someway redistribute the peel stress on the bondline.

Effect of Lap Joint Width to the Shear and Peel Stress Distribution of Bi-Adhesive

A single lap joint is one of the most popular types of adhesive joints. This joint is very easy to apply and gives satisfactory results. However, there is an extensive shear stress distribution at both ends in a single lap joint and shallow in the middle. In this research, the performance test of the bi-adhesive with different joint widths was carried out. We modelled with 2D FEM consisting of adherent aluminum, two adhesives DP490 and ESP110 and then performed a static test to obtain shear and peel stress distribution. The results presented that using a bi-adhesive improved the shear stress distribution compared to a single adhesive individually. By adjusting the length ratio of each adhesive, the optimum conditions will be obtained. The peak stress will decrease, and the stress distribution will be better. In addition, the wider the lap joint, the stress distribution will be more evenly distributed. The peak stresses at the ends and in the middle of the joint are getting smaller in both the single adhesive individually and the bi-adhesive. This result is a recommendation for the user to increase the strength of the adhesive joint.

Performance assessment and optimization of hybrid composite patch repair of aircraft structure

PurposeIn this article, a novel hybrid composite patch consisting of unidirectional carbon fiber and glass fiber is considered for repair of the aircraft structure. The purpose of this paper is to assess the performance of hybrid composite patch repair of cracked structure and propose an optimized solution to a designer for selection of the appropriate level of a parameter to ensure effective repair solution.Design/methodology/approachElastic properties of the hybrid composites are estimated by micromechanical modeling. Performance of hybrid composite patch repair is evaluated by numerical analysis of stress intensity factor (SIF), shear stress, and peel stress. Design of experiment is used to determine responses for a different combination of design parameters. The second-order mathematical model is suggested for SIF and peel stress. Adequacy of the model is checked by ANOVA and used as a fitness function. Multiobjective optimization is carried out with a genetic algorithm to arrive at the optimal solution.FindingsThe hybrid composite patch has maintained equilibrium between the SIF reduction and rise of the peel stress. The repair efficiency and repair durability can be ensured by selection of an optimum value of volume fraction of glass fiber, applied stress, and adhesive thickness.Originality/valueThe composite patch with varying stiffness is realized by hybridization with different volume fraction of fibers. Analysis and identification of optimum parameter to reduce the SIF and peel stress for hybrid composite patch repair are presented in this article.

Analysis and optimization of ultrasonic copper wires using fuzzy logic approach

Ultrasonic welding has been used in the market over the past thirty years and offer to the manufacturing industries like automotive, aviation, medical and many more due to various hurdles faced by conventional fusion welding or crimp processes. Very short time (less than 1 second) and no additional material during the connection process are very key advantages. Due to this fact this technology can be used for mass production. Plenty of times, the problems faced by industry due to this process are the poor weld quality and strength of the joints surface. In presented study, the process parameters like vibration amplitude, weld pressure and weld time are considered in analysis of the welding of copper wires (Cu- ETP1). Experiment is conducted according to the fractional design with replications to get the responses like tensile shear stress and T-peel stress of the weld. Measured data are utilized next to develop fuzzy logic model between responses and predictors. As a quality is an very important issue in these manufacturing industries, the optimal combinations of studied process parameters are found using fuzzy logic approach.

Effects of Adhesive Bond on Active Repair of Aluminium Plate Using Piezoelectric Patch

Research activities on active repairs and stress control of structures using piezoelectric actuators and adhesive bond have received much attention in recent years. The function of the adhesive bond on active repair is to transmit the induced stresses by the piezoelectric actuator to the host structure in order to reduce the stress intensity on the crack front. Assessment of repair performance of adhesive bonds is done based on the transfer of the shear and peel stress concentration in the adhesive layer. In the present work, three dimensional finite element analyses have been carried to understand the effects of adhesive properties on active repair performance of a cracked aluminium plate under mode I. Adhesive efficiency is evaluated by the stress intensity factor (SIF) as a fracture criterion. The results show that SIF varies inversely with the adhesive layer’s shear modulus.

Interlaminar Stress Distributions of Notched Quasi-Isotropic AS4/PEEK Laminate

This paper investigates the interlaminar stress distributions of notched angle-ply thermoplastic laminate under tension numerically. The representative AS4/PEEK laminate with configuration of was studied by finite element code ANSYS. Computation results show: The interlaminar stress concentrations are evident and localized in the vicinity of the hole and the two free sides, and the maximum values always appear near the hole. Meanwhile, at interfaces of-45/+45 and +45/0, the concentration of peel stress is evident, while at interfaces of 90/-45 and 0/90, the concentration of shear stress is evident. Further analysis demonstrates interlaminar shearing stress is the dominating stress and may be the leading cause of laminate delamination.