Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

Repair procedures with the use of composite patches are considered to be the most effective among the current technologies of repair of the structures of various applications. In the process of moulding-on of a patch made of polymeric composite material by means of curing, technological stresses arise in the patch. Determination of residual technological stresses is a priority task for the modelling of the repair process. Reduction of residual stresses can be achieved by optimization of the mode of repair patch curing. For meeting this objective, the method for determination of technological stresses, which arise in the structure under repair in the process of curing of a composite patch, has been developed. The method takes into account the shrinkage, change in physico-mechanical characteristics, rheological processes occurring in the binder during moulding process, and determination of stresses in the structure under repair at any time. Therefore, premature failure of the repair joint at the stage of repair can be avoided. It is shown that the method adequately describes the level of deformations and stresses in the structure being repaired at the stage of heating and holding of the composite patch. Increase in the moulding temperature leads to a reduction in residual stresses in the structure under repair. However, current stresses at the stages of heating and temperature holding are increased significantly. Reliability of assumptions and developed method is confirmed by the comparison with the experimental data. The obtained experimental graph of total deformation of the composite patch allowed us to clearly determine the moment of residual stress occurrence in the structure under repair. This moment matches quite exactly (with the discrepancy not exceeding 5 min) the gel point determined analytically based on dependence of the degree of curing on the moulding mode. Consequently, the research together with the results previously obtained allows making an integrated choice of geometric parameters of the repair composite patch and temperature–time regime of its curing in order to ensure the specified level of strength and stiffness of the structure under repair.

ANALYSIS OF EFFECT OF TEMPERATURE CHANGE ON WOOD POLYMER COMPOSITE MATERIAL

In this work the research of new wood polymeric composite material as which filler timber industry waste in the form of sawdust, shaving, spill, lumpy waste and polyethyleneterephthalate, a research of its frost resistance by means of a method of a computer experiment is used is considered. A computer program has been developed to simulate the structure and physical properties of building blocks made of wood polymer composite material. The program allows you to set geometric and physical parameters of the building block and material components in the windows of the interface form in program code, as well as test conditions for cyclic heating and cooling to temperatures maximum possible during operation, and investigate the influence of parameters on the internal and surface destruction of the building block. The program is applicable for a wide range of concentrations of composite components, geometric parameters of the building block, various mechanical and thermocyclic tests. Influence of composition of wood polymer composite material on structure in thermocyclic tests is investigated. Dependencies of broken bonds on concentration of wood, cartogram of breaking bonds of wood polymer composite material with concentration of wood from 20 to 80% are obtained.

Structural model of heterogeneous material (microsphere foam) straining and failure under hydrostatic loading

Object and purpose of research. The paper investigates polymeric composite material of syntactic foams type being by nature a heterogeneous medium and consisting of polymeric matrix, filled with spherical inclusions: microspheres. The main purpose of this this paper is to develop a structural model of straining and failure for this type of materials under hydrostatic pressure and software and mathematical apparatus for model implementation. Materials and methods. The input data for this research were composition and structure of syntactic foam material as well as the performance of its components (polymeric matrix and glass microspheres). Structural model was developed on the basis of solutions to linear elasticity theory problems using Lubachevsky – Stillinger algorithm for the formation of structure, homonization methods, etc. A calculation algorithm implemented in code in the С++ language was developed on the basis of the designed mathematical apparatus. Verification of calculation results was carried out by comparison with failure test results of samples of one of the grades of syntactic foam under short-term hydrostatic pressure loading. Main results. Structural model of syntactic foam type material straining and failure under hydrostatic pressure was developed. A calculation algorithm implemented in program code written in the С++ language which is relatively highly efficient for analysis of real structures with a large number of microspheres of the order of 105. Correlation with experimental results showed compatibility of modelling results in terms of both quantitative and qualitative estimates. Conclusion. The developed structural model allows with a high degree of confidence to describe the processes of damage and failure accumulation in syntactic foam under hydrostatic pressure. For practical purposes the model can be used applied for prediction of syntactic foam performance (strength, bulk strain and buoyancy), based on the properties of the initial components – microspheres and polymeric matrix.

Flexural behavior of functionally graded polymeric composite beams

The bending test is one of the most important tests that demonstrates the advantages of functional gradient (FGM) materials, thanks to the stress gradient across the specimen depth. In this research, the flexural response of functionally graded polymeric composite material (FGM) is investigated both experimentally and numerically. Fabricated by a hand lay-up manufacturing technique, the unidirectional glass fiber reinforced epoxy composite composed of ten layers is used in the present investigation. A 3-D finite element simulation is used to predict the flexural strength based on Hashin’s failure criterion. To produce ten layers of FGM beams with different patterns, the fiber volume fraction ( Vf%) ranges from 10% to 50%. A comparison between FGM beams and conventional composite beams having the same average Vf% is made. The experimental results show that the failure of the FGM beams under three points bending loading (3PB) test is initiated from the tensioned layers, and spread to the upper layer. The spreading is followed by delamination accompanied by shear failures. Finally, the FGM beams fail due to crushing in the compression zone. Furthermore, the delamination failure between the layers has a major effect on the rapidity of the final failure of the FGM beams. The present numerical results show that the gradient pattern of FGM beams is a critical parameter for improving their flexural behavior. Otherwise, Vf% of the outer layers of the FGM beams, i.e. Vf% = 30, 40, or 50%, is responsible for improving their flexural strength.

Recent Advances in Biopolymeric Composite Materials for Tissue Engineering and Regenerative Medicines: A Review

The polymeric composite material with desirable features can be gained by selecting suitable biopolymers with selected additives to get polymer-filler interaction. Several parameters can be modified according to the design requirements, such as chemical structure, degradation kinetics, and biopolymer composites’ mechanical properties. The interfacial interactions between the biopolymer and the nanofiller have substantial control over biopolymer composites’ mechanical characteristics. This review focuses on different applications of biopolymeric composites in controlled drug release, tissue engineering, and wound healing with considerable properties. The biopolymeric composite materials are required with advanced and multifunctional properties in the biomedical field and regenerative medicines with a complete analysis of routine biomaterials with enhanced biomedical engineering characteristics. Several studies in the literature on tissue engineering, drug delivery, and wound dressing have been mentioned. These results need to be reviewed for possible development and analysis, which makes an essential study.

The interrelation between physical and mechanical properties of the polymeric composite and fractal dimension of structural elements its surface

The paper shows the promising use of the "fractal dimension" parameter for qualitative and quantitative analysis of the surface structure of samples based of micrographs obtained by scanning electron microscopy and atomic force microscopy. The interrelation of this parameter with some mechanical characteristics of polymeric composite material PTFE-3%tu121 is investigated.

POLYMERIC COMPOSITE MATERIAL FOR BONE IMPLANTS WITH THE FEASIBILITY OF INTRAOPERATIVE FORM CORRECTION

A biomimetic composite material based on polylactide (PLA), polycaprolactone (PCL) and hydroxyapatite (HAP) with high biocompatibility and osteoconductive properties was developed. The structural and mechanical characteristics of the material were investigated and in vitro and in vivo studies were carried out.

Preparation and Characterization of Silk Fibroin-Based Hybrid Vascular Tissue Engineering Film

Patients suffering from cardiovascular disease lack suitable stent. In this study, a new polymeric composite material was prepared by incorporating various concentrations of gamma-glycidoxypropyltrimethoxysilane (GPTMS) into silk fibroin (SF), aiming at achieving a novel composite film with superior mechanical and biological properties, in order to match the requirement of cardiovascular tissue engineering stents. Fourier transform infrared spectroscopy (FTIR) analysis showed that GPTM could promote SF to transform from the original alpha helix and random coil/extension chain conformation to the beta-folded conformation. Tensile experiment indicated tensile strength and breaking elongation of SF/GPTMS hybrid film reach the maximum with 20% GPTMS content. Within a certain range, the water drop contact angle of SF/GPTMS hybrid film is positively correlated with the content of GPTMS. Endothelial cells (ECs) are best grown on hybrid SF/GPTMS hybrid film with 20% GPTMS content.