Exercise on composites please. this is going to be in my exam

In summary, the conversation discusses the use of a glass-reinforced polyethylene composite material in a high-pressure water-jet cleaning system. The participants discuss the calculation of the hose's percentage increase in length and diameter when pressurized, as well as the stress level in the glass fibers using the rule of mixtures. The estimated stress in the glass fibers is 20 MPa.
  • #1
Chemist20
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Exercise on composites << please. this is going to be in my exam!

PLEASE. I really need this! (im preparing the course by myself and have no one to ask to!

a hose in a high-pressure water-jet cleaning system is to be made of a glass-reinforced polyethylene composite material,with continious fibers (Vf=0.4) orientated in the hoop direction. The hose has a external diametre of 20 mm and a wall thickness of 2mm. The water pressure during operation is 10 MPa. Calculate the percentage increases in length and diametre of thehose when it is pressurized

I did that and I got that the hoop stress was 50 MPa and the axial one 25 Mpa. The strain in length due to axial stress is 1.68% and in the diametre 0.16%.

Estimate the stress level in the glass fibers when the hose is under pressure

this is what I don't get! I got aprox 150 Mpa but it's wrong.
 
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  • #2
The stress in the glass fibers when the hose is under pressure can be calculated using the rule of mixtures. The rule of mixtures states that the total stress in the composite material is equal to the sum of the stresses in each component, multiplied by their respective volume fractions. Therefore, the stress in the glass fibers is (50 MPa) x (0.4) = 20 MPa.
 

1. What are composites and how are they used in exercise equipment?

Composites are materials made up of two or more different components that work together to create a stronger material. In exercise equipment, composites are commonly used to make lightweight and durable products such as carbon fiber bikes or fiberglass kayaks.

2. What are the benefits of using composites in exercise equipment?

Composites offer many benefits in exercise equipment, including strength, durability, and lightweight. They also have the ability to be molded into complex shapes and can be tailored to meet specific performance requirements.

3. Are there any disadvantages to using composites in exercise equipment?

One potential disadvantage of using composites in exercise equipment is the higher cost compared to traditional materials such as steel or aluminum. Additionally, composites may be more difficult to repair if damaged.

4. How do composites compare to other materials commonly used in exercise equipment?

Composites offer several advantages over other materials commonly used in exercise equipment. They are typically lighter, stronger, and more durable than traditional materials. However, they may also be more expensive and require specialized manufacturing processes.

5. Are there any safety concerns associated with using composites in exercise equipment?

Composites used in exercise equipment are generally considered safe. However, it is important to follow manufacturer's instructions and properly maintain the equipment to prevent any potential safety hazards. It is also recommended to regularly check for any signs of damage or wear in the composite components.

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