Nano composite materials based on polymers are widely used in restoration martials like dental. Poly methyl methacrylate (PMMA) is one of the most used polymers as dental material. PMMA has disadvantages such as low flexural strength properties and impact strength. In this paper, the influences of additive aluminum oxide and hydroxyapatite nanoparticles on the mechanical and strength properties of PMMA (including flexural strength, impact strength, surface hardness and shrinkage behavior) is studied experimentally. For this purpose, nine standard mechanical testing samples of pure PMMA, PMMA/5HA and PMMA/10HA with various amounts of Nano aluminum oxide (3,6,8 wt.%) were prepared. The results showed that the mechanical properties of hybrid Nano-composites were significantly improved in comparison with the pure samples in a way that optimal Nano-composite with convenience flexural properties and impact strength is obtained. Moreover, the use of nanoparticles results in shrinkage reduction of hybrid Nano-composites in comparison with pure PMMA.

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A loss of integrity and the effects of damage on mechanical attributes result in macro/micro-mechanical failure, especially in composite structures. As a progressive degradation of material continuity, predictions for any aspects of the initiation and propagation of damage need to be identified by a trustworthy mechanism to guarantee the safety of structures. Besides material design, structural integrity and health need to be monitored carefully. Among the most powerful methods for the detection of damage are machine learning (ML) and deep learning (DL). In this paper, we review state-of-the-art ML methods and their applications in detecting and predicting material damage, concentrating on composite materials. The more influential ML methods are identified based on their performance, and research gaps and future trends are discussed. Based on our findings, DL followed by ensemble-based techniques has the highest application and robustness in the field of damage diagnosis.

Estimation of mode II fracture toughness KIIC in composite materials is known as a troublous and crucial problem. Dissipated values of KIIC that are reported in different fracture mechanics references is the evidence of the mentioned claim. This problem can signify the necessity of modification on common test methods and fixtures. The present study focuses on the causes of shear test results scattering in composite materials and presents some solutions in the form of necessary corrections that should be performed on the common test fixtures. Mixed mode I/II fracture limit curves are employed to show that the scattering in test results have strong relation with the creation of a considerable Fracture Process Zone FPZ. It is shown that common test fixtures are blind in confrontation with FPZ and are not able to active toughening mechanisms in pure mode II, correctly. Therefore, estimation of KIIC with available test fixtures has considerable standard deviation. After that, by employing some structural modifications on common fixtures, a new scheme of a shear fixture is proposed that in addition to include the FPZ effects, prepare suitable condition in order to activate the mode II toughening mechanisms. In this regard, it could be found that by applying these reforms, shear load concentration as well as the accuracy of empirical test and repeatability and reproducibility are enhanced. Furthermore, a 3D finite element method FEM was considered as the numerical method in which the Iosipesque and new fixture's specimens were analyzed by ANSYS software. It was found that by applying major amendments in the new shear test fixture, a remarkable precision in results can be obtained in comparison with the previous Iosipesque one

ABSTRACT. Performance of Friction Stir Welding (FSW) as a solid-state process is approved in several engineering applications, especially aluminum industries. Identification of mechanical behavior of the associated welded zone is necessary due to these extensive applications of FSW. In this study, considering the effect of rotational and forward speed of welding tool on the mechanical properties of welded region, a hybrid optimization method based on combination of Genetic Algorithm (GA) and Response Surface Method (RSM) named here as GA-RSM is proposed to achieve maximum tensile and ultimate strength. The results of GA-RSM are validated by per-forming necessary experimental tests on two wide-used 2024 and 5050 aluminum alloys. The results show that GA-RSM could be an effective approach to achieve optimized process for FSW with minimum cost.

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In-plane strength and constitutive properties of composite materials is known as crucial problems. Although, several studies have been made for obtaining the in-plane mode II properties, the common test fixtures are blind in confrontation of shear zone. Furthermore, toughening mechanisms and consequently mode II fracture toughness cannot be evaluated, precisely. Also, proposing the convenient configuration of shear test fixture increase the accuracy of evaluation for the shear-zone energy dissipation, especially in orthotropic materials. Hence in the present research, a novel shear fixture configuration is proposed based on Iosipesque structural modification. Hereof, some arbitrary composite materials (e.g. graphite/epoxy and wood) were studies on the basis of DOE and E-691 ASTM. Furthermore, as the numerical method for indicating the comparison of the uniform and non-uniform shear stress distribution in the modified and common shear test fixture, a statistical procedure is used based on ASTM standard in addition to FEM analysis. The obtained results reveal that applying major amendments through the new scheme of the shear test fixture, would provide a remarkable precision and a reasonable estimation of the shear strength in comparison with the previous Iosipesque experiments.