25 Questions
What type of failure mode is associated with Tension in fibre-reinforced composites?
Matrix cracking
Which fabric type can help control composite anisotropy and save time during the lay-up process?
Woven
In a stress-strain curve of a fibre composite with a tough but weak matrix and brittle but strong fibres, what does a high interfacial strength favor?
Matrix deformation
What is the primary role of a lightweight core material in sandwich materials?
Increase flexural strength
For brittle matrices, why is a low interfacial strength desirable?
Interfacial de-bonding
What is the purpose of applying vacuum pressure during the vacuum bagging process?
To help consolidate the composite pre-form
Which is a potential advantage of using filament winding over other techniques?
Fast and economic fibre impregnation
Why is it safer for workers during vacuum bagging?
Toxic volatiles are removed by vacuum
What is a disadvantage of using vacuum bagging as a manufacturing process?
The extra process adds cost
How does filament winding control the resin content of the final product?
Nip rollers and dies can be used to control resin content
What is the main advantage of the pultrusion process?
Fast and economic impregnation and curing of materials
What is a limitation of the resin transfer moulding process?
High set-up costs
Which characteristic makes pultrusion favorable for mechanical properties?
Fibres are straight, highly aligned and have a high volume fraction
What does VARTM stand for in the manufacturing process described?
Vacuum Assisted RTM
Why are large mandrels considered costly in the pultrusion process?
To align fibres more effectively
What is a key advantage of resin transfer moulding mentioned in the text?
Ability to produce high fibre volume laminates with low porosity
What is a major disadvantage of resin transfer moulding according to the text?
Unimpregnated areas leading to expensive scrap parts
Why are prepregs preferred over conventional lay-up techniques as per the text?
Maximum strength properties and reduced brittleness
What is an advantage of using prepregs in terms of cosmetics mentioned in the text?
Smooth, glossy surface is easily attainable
Why are prepregs considered expensive according to the text?
High cost of equipment for prepreg production
What type of polymers become soft and mouldable when heated?
Thermoplastic polymers
Which type of polymers can only be reinforced with short fibres or whiskers due to their very high viscosity?
Thermoplastic polymers
What is a key property that a polymer matrix for composite applications must possess?
Resistance to environmental degradation
Which type of polymers form as a result of a non-reversible chemical reaction from liquid resin and catalyst?
Vinylester polymers
Why are thermoset polymers suitable for continuous fibre composite manufacture compared to thermoplastic polymers?
Because they have much lower viscosity during processing
Study Notes
- Pultrusion is a process for producing continuous fiber reinforced polymer composite extrusions where multiple fibers are pulled through a resin bath, coated, and then cured in a heated die before being cut into desired lengths for applications like beams and girders.
- Pros of pultrusion include fast and economic impregnation, accurate resin control, straight and highly aligned fibers with high volume fraction, and enclosed resin impregnation area for limiting volatile emissions; cons include unidirectional fibers, high setup costs, and limited geometric variety.
- Resin transfer molding involves laying fiber fabrics in a mold, injecting resin at high pressure, and using vacuum suction for resin infiltration, resulting in high fiber volume laminates with low porosity and the ability to create geometrically complex moldings.
- Prepregging is the process of pre-impregnating reinforcement fibers with resin, offering maximum strength properties, uniformity, reduced waste, and improved cosmetics compared to traditional lay-up methods; however, prepregs are expensive.
- The strength of the reinforcement/matrix interface in fiber reinforced composites affects failure modes like tension, compression, matrix cracking, and fiber cracking.
- Sandwich materials involve a lightweight core covered by skin sheet materials to increase flexural strength and allow for thicker composite components; vacuum bagging aids in producing higher fiber content laminates with better strength but adds cost and requires a higher skill level.
- Filament winding is used for producing hollow cylindrical products by coating fiber tows in resin and winding them onto a rotating mandrel, offering fast and economic fiber lay-down with the ability to control resin content.
Test your knowledge on the various failure modes of fibre reinforced composites and the types of fabric used in composite production. Explore topics such as tension matrix cracking, shear, compression, and stress-strain curve of fibre composites.
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