Mech 425 assignment 1

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Concordia University *

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425

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Mechanical Engineering

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Dec 6, 2023

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Khalif Ortega Beckles 40130010 MECH 425 Homework 1 1. (5 marks). Indicate four main functions provided by the matrix in a composite material. Indicate the main functions provided by the fiber in a composite material. The matrix serves the following functions: - Aligning the fibres - Transfer the load between the fibers - Assisting the fibres in providing compression, shear strength and modulus to the composites - Protecting the fibers from environmental attack The main function provided by the fiber in the composite material is that it provides strength and stiffness. 2. (5 marks). Indicate the four most common manufacturing processes for making components using thermoset composite materials. For each process, indicate which sector of the industry that the process is used the most. Give a reason why this is so. The four main manufacturing processes for making components are: - Hand-lay-up which is commonly used in the aerospace industry because the components made are mostly thin flat plate or shallow shells with free edges - Filament winding is mostly used in making composite pressure vessels since they are cylindrical or spherical and usually have no free edges - Pultrusion is used to make structures in the civil engineering applications and are commonly used for components having a constant cross section along the length - Liquid composite molding is used to make automobile composite components these components tend to be complex 3D configurations 3. (5 marks). Indicate in what way manufacturing using composites is different from the manufacturing using metals. Manufacturing metals and composites differ in that for metals they come in slabs or sheets and different processes like cutting, bending, welding, etc are used to get the finished product. For composites the manufacturer they work with the fibers and matrix to make the finished product directly. They have the fibers and matrix, then they combine them into single layers, afterwards they stack the individual layers on top of each other and finally they use a manufacturing process such as hand-lay-up, filament winding, pultrusion, etc to get the final product. 4. Why is wetting of the fibers important? What are the two most important aspects that affect wetting of the fibers?

Wetting in the fibers is important because you want to avoid dry spots which can become areas of stress. The two important aspects that are affected by wetting the fibers are availability of the resin for the fibre and compatibility between the fibre and the matrix. 5. (5 marks). Using the square packing array, show that the interfiber spacing is given by: V f = ( n 2 ∗ d f 2 ∗ π 4 ) a 2 a = n ∗ d f + nδ V f = ( n 2 ∗ d f 2 ∗ π 4 ) ( n ∗ d f + nδ ) 2 √ V f = n ∗ d f √ π 4 n ( d f + δ ) d f + δ = d f ∗ √ π 4 ∗ V f δ = d f ( √ π 4 ∗ V f − 1 ) 6. (5 marks). What is the general difference between the viscosity of thermoset resins ( in general as a group) and thermoplastic resins ( in general as a group). What is the implication of this phenomenon on the manufacturing strategy? The difference between the viscosity of the thermoset resin and the thermoplastic resins is that the thermosets such as polyesters, vinyl esters and epoxies have low viscosities at low temperatures close to 1 Pac-sec at room temperature while the viscosity of thermoplastics are very high around 1000 Pac-sec. Due to the fact previously mentioned, there are more composites with thermosets rather than thermoplastics even if thermoplastics can offer better properties such as fracture toughness and environmental resistance 7. (5 marks). What are the three important advantages that a material (like glass material) existing in fiber form over the same material in bulk form? The important advantages that exist in fiber form over the same material in bulk form are: - Strength of material in fiber format is better compared to bulk format - Availability of more fabrication techniques

- Flexibility in forming

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