Statement of the problem: Poly methyl methacrylate (PMMA) acrylic resin, although being the most popular denture base material, is associated with poor mechanical properties. It has been documented that acrylic resin can be strengthened with an addition of structural component (filler) added in the acrylic matrix, to form a composite structure. Objective: To evaluate and compare the transverse strength, impact strength, surface hardness and water sorption of 10% and 20% zirconia (ZrO 2 ) reinforced high impact acrylic resin with that of high impact acrylic resin (Trevalon HI, Dentsply India). Materials and methods: There were 30 specimens in each of the four tests, amounting to a total of 120 specimens. Each of the tests had 10 specimens fabricated from high impact acrylic resin (control); 10 specimens fabricated from 10% zirconia (ZrO 2 ) and 10 specimens fabricated from 20% zirconia (ZrO 2 ) reinforced high impact acrylic resin. Specimens were subjected to the test of transverse strength in Universal Testing Machine, impact strength in Izod pendulum impact testing machine and surface hardness by Vickers Microhardness tester according to ISO Specification No. 1567. Water sorption was assessed according to ADA Specification No. 12. Data were analyzed by means This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). of a one-way ANOVA and Bonferroni multiple comparison test. Results: A significant increase in the transverse strength was observed in the reinforced specimens when compared to the control group. Impact strength and surface hardness were found having lesser values compared to the control group. Water sorption was found to increase on the addition of 10% and 20% zirconia (ZrO 2 ) but the value lied below 0.8 mg/cm 2 i.e. within the limit of ADA Specification No. 12. Conclusion: Reinforcement of acrylic resin with zirconia powder affects its physical and mechanical properties significantly. ª 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Advanced fabric reinforced polymer composites find extensive applications in aerospace and structural fields due to their high mechanical properties. A novel stamp forming technique finds extensive use in the hemispherical forming of thermoplastic composites. This study investigates the influence of stamp forming parameters on the formability of thermoplastic composite using Taguchi's robust design and grey relational analysis. Taguchi's orthogonal array was used for designing the forming experiments. Responses such as forming ratio and logarithmic thickness strain were considered for the assessment of sheet formability through single and multi-response optimization. Analysis of variance was used for the determination of the contribution of each parameter on formability and it was identified that the die temperature acts as a prominent factor, followed by blank holder force and blank temperature. The confirmation test was conducted at optimum parameter levels and the obtained experimental grade was seen within the confidence interval of the predicted value.

Thermoplastic composites are broadly utilized for structural and automotive applications due to their higher specific strength and modulus, higher strain to failure, recyclability, and unlimited shelf life. This study investigates the effects of fabric structure on the forming behaviour of glass fabric reinforced polypropylene composites during the sheet forming of a doubly curved shape. Stamp forming, a novel thermoforming technique, is mostly used for hemispherical forming of thermoplastic composites. The study also investigates the influence of process parameters such as die temperature, blank temperature, and blank holder force on sheet formability. Forming ratio, thickness distribution, material draw-in, and punch force were used for the evaluation of the formability of composites. Conventional and novel plain weave glass fabric reinforced polypropylene composite laminates were fabricated using the film stacking technique. Thermo-stamp forming experiments were conducted on the basis of the Taguchi’s L9 orthogonal array. Experimental results revealed better forming characteristics by the novel glass fabric reinforced composite than for the conventional glass fabric reinforced composite. Production of defect-free components under high die temperature, low blank holder force, and medium blank temperature process condition was observed.

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Various multilevel inverter topologies are widely being used for real power exchange, reactive power compensation, harmonic current mitigation on grid and industrial drive applications with fundamental frequency switching mode of gate control. Still so many topologies are being currently developed with reduced number of switches, improved waveform for power quality improvement with fundamental frequency switching and pwm switching gate control mode. This paper presents the performance analysis of modified H-bridge single phase inverter for high voltage and high power applications. The switching method has been selected to operate the inverter at fundamental frequency switching mode of gate control to be free from lower order harmonics. The inverter has the modulation technique with pre calculated switching angles to generate the required fundamental voltage with reduced Total Harmonic Distortion (THD). So, the switching losses have been reduced hence the efficiency is improved with Power Quality (PQ) improvement in voltage-current waveform. The DC input power is feed to the inverter from DC capacitor voltage divider source, contributed to give various dc voltage levels during fundamental frequency switching of different switching combinations for the generation of stepping output voltage. During dynamic load condition, the magnitude of input dc voltage level across each capacitor has not undergone through big swing to feed the power to the load without affecting generated output ac voltage. The performance of the proposed inverter has been analyzed for dynamic reactive load and induction motor. The MATLAB based simulations have been presented to validate the inverter operation for dynamic reactive load and industrial drive applications with pre calculated THD reduced switching conduction angles for PQ improvement in waveform.

Recently, the forming of thermoplastic composite (TPC) sheets has been receiving the attention of researchers. Woven fabric TPCs have been successfully utilized in automotive, aerospace and defense industries, due to their high formability and strength. Hence, to optimize the forming process, it is essential to understand the mechanical behavior of the woven fabric and accordingly, various appropriate numerical methods are developed. A reliable simulation tool for forming is needed to obtain the optimum processing parameters, in which parts can be formed without defects, such as wrinkles. This paper explores the experimental, numerical and theoretical works conducted by many researchers to investigate the formability of TPC sheets.