CFRP structures are often exposed to humid environment resulting in water absorption and causing property degradation. Water swelling and its effect on tensile, compressive, and flexural properties were investigated according to ASTM standards. Fracture modes were evaluated by analyzing micrographs of fracture areas. The specimens were cut from twill wave CFRP composite plates fabricated using a vacuum infusion technique. Some of them were immersed in water prior to being mechanically tested. It was found that tensile strength, as well as compressive, and flexural strength and moduli decreased due to water swelling, but fracture strain was found to increase due to water swelling. The most severely affected by water swelling is flexural strength (decreased by 25.72%), and the least is compressive modulus (decreased by 1.89%). Tensile specimens underwent fibre breakage followed by matrix cracking, compressive and flexural specimens showed fibre buckling followed by kinking and crushing where flexural specimens failed in their compressive side. In conclusion, water absorption has a bad impact on the composite strength.
The purposes of this research are to formulate the mathematical model of the system, to propose an effective control scheme and to perform experiments on a laboratory scale. The system used in this paper consists of a trolley, a pendulum as load and a dc motor to drive the trolley. Mathematical model of trolley position and load angle were formulated considering voltage of the motor and damping constant of the air calculated specifically using energy balance. Two proportional (P) controllers were designed in parallel in such a way to drive the trolley and to reduce oscillation of the load. The system and the proposed control scheme were confirmed through experiments. The experimental results revealed that the motion and oscillation of the system can be controlled effectively.
The development of Microcontroller-Based Water Level and Temperature Control is the development of Microcontroller-Based Water Level Control Design. This equipment is a tool that can be used to monitor and control the level and temperature of water. The aim of this research is to make a water level and temperature control device based on microcontroller, and to display the information of water level and temperature on the computer. The research methods used during the implementation process of this research are : literature study, hardware and software design, and data retrieval. The Microcontroller-based Water Level and Temperature Control uses two sensors, namely : ultrasonic sensor to detect water level, then the second sensor is a thermocouple sensor which is used to detect water temperature. This equipment uses a water pump to flow water from one tank to another, and the heater that used to heat water. The device has 2 buttons, where the first button is used to control the water level, and the second button is used to control the level and temperature of the water. Based on the results of the study it can be concluded that this water level and temperature control system works well as expected, where this equipment uses a multi position control system mode that has been programmed in the Arduino software and can display sensor readings in the form graphs using matlab software.
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