This set of Composite Materials Multiple Choice Questions & Answers (MCQs) focuses on “Liquid Composite Moulding Process”.
1. Which is not a liquid composite molding process?
a) Resin transfer molding
b) Reaction injection molding
c) Vacuum-assisted resin injection molding
d) Compression molding
View Answer
Explanation: The liquid composite molding comprises various types of processes such as Resin transfer molding, reaction injection molding, Vacuum-assisted resin injection molding, Seemann’s Composite resin infusion molding process etc. While Compression molding is entirely a different type of composite molding process.
2. In the liquid composite molding process, a premixed liquid resin is infused or injected into a dry fiber preform in a closed mold in a liquid.
a) True
b) False
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Explanation: When the premixed resin is injected into the dry fiber preform, the liquid spreads through the preforms, fills the space between the preforms, eliminates the air and at last it cures and transforms into the matrix part. This is the basis of all liquid composite molding processes.
3. In Resin transfer molding, the catalysed liquid resin is injected into the mold through ___________
a) sprue
b) runner
c) riser
d) core
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Explanation: The sprue is the passage through which catalysed liquid resin is injected into the mold. Whereas a runner connects sprue to the riser, the core is used to produce internal cavities and the riser acts as a reservoir of the liquid resin.
4. Curing is performed either at an elevated temperature or at room temperature depending on ________
a) resin-catalyst system
b) resin
c) catalyst
d) fibers
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Explanation: Curing is performed either at room temperature or at an elevated temperature in an air-circulating oven depending upon the resin-catalyst system. The chemical reaction rate is altered by the change in temperature.
5. Liquid composite moulding allows fast and high-quality production of advanced composites.
a) True
b) False
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Explanation: Liquid composite molding processes are capable of producing complex-shaped, high-quality composite products. So, they are used mainly in the aerospace, marine, automotive and civil industries. Moreover, a higher number of products could be produced since the operations are simpler than other composite manufacturing processes.
6. Which is not a method for producing fiber preforms?
a) Spray-up process
b) Stamping operation
c) Hand lay-up process
d) Cut and sew method
View Answer
Explanation: Composites use fiber preforms constructed from tows or yarns which are arranged in complex 3-D structures. Preforms can be created from a braiding process, weaving process, lay of short fibers using spray-up process, whereas hand lay-up process is a composite fiber reinforcement placement process in a mold.
7. The best method for making preformed fibers from continuous strand mats is _____
a) stamping operation
b) spray-up process
c) cut and sew method
d) braiding operation
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Explanation: Continuous strand mats containing random fibers can be performed using a simple press and a pre shaped die by stamping operation method. Both thermoset and thermoplastic binders are available for regaining the formed shape after stamping operation.
8. _________ is particularly suitable for producing tubular preforms.
a) Spray-up process
b) Cut and sew method
c) Stamping
d) Braiding
View Answer
Explanation: Many tubular parts, parts used in ship-building, defence are the application of the braiding process. Braiding process is also used to produce 2 or 3-dimensional preforms.
9. RTM has a very high tooling cost and complex mold clamping requirements compared to compression-molding.
a) True
b) False
View Answer
Explanation: Compared with the compression-molding process, RTM has a very low tooling cost and simple mold clamping requirements. In some cases, the two mold halves are held together by a series of nuts and bolts or a ratchet clamp. Also, RTM is a low-pressure process, and therefore in low-tonnage presses parts can be resin transfer molded.
10. The starting material in an RTM process can be a preform that already has the shape of the desired product.
a) True
b) False
View Answer
Explanation: The advantages of using a preform instead of flat-reinforcing layers, are good molding ability with complicated shapes and the elimination of the trimming operations, which is often the most labour-intensive step in an RTM process.
11. Which is the most cost-effective composite molding process?
a) Bag molding
b) Resin transfer molding
c) Compression molding
d) Filament winding
View Answer
Explanation: Resin transfer molding offers a cost-saving alternative to the capital-intensive compression-molding process and the labour-intensive bag-molding process. The RTM process has been successfully used in molding parts like chairs, cabinet walls, water tanks, hoppers, boat hulls and bathtubs. Since the process operations are simpler mass production is feasible for RTM.
12. Which is not a variation of the basic resin transfer molding process?
a) HP-RTM
b) VARTM
c) SCRIMP
d) SRIM
View Answer
Explanation: SRIM stands for Structural Reaction Injection Molding. It is similar to the RTM process, but the difference is mainly in the reactivity of the resin. HP-RTM is High-Pressure Resin Transfer Molding which is RTM process equipped with high pressures, VARTM is vacuum-assisted RTM process where vacuum is used in addition to the resin injection systems and SCRIMP stands for Seemann ’s Composite Resin Infusion Molding Process where a porous layer is placed on the preform to distribute the resin uniformly throughout the preform.
13. The difference in Resin Transfer molding(RTM) and Structural Reaction Injection Molding(SRIM) is mainly in the resin reactivity.
a) True
b) False
View Answer
Explanation: The resin reactivity of SRIM resins is much higher than that of the RTM resins. In the SRIM process, two low-viscosity and highly reactive liquid streams are mixed with each other at high speeds in a chamber quickly before injecting the liquid mix into the mold cavity.
14. What does SCRIMP stand for?
a) Seemann’s Composite Resin Infusion Molding Process
b) Seemann’s Composite Resin Injection Molding Process
c) Structural Composite Resin Injection Molding Process
d) Structural Composite Resin Infusion Molding Process
View Answer
Explanation: SCRIMP is a patented process named after William Seemann, it’s inventor. Vacuum is also used in SCRIMP to pull the liquid resin into the dry fiber preform. Moreover, a porous layer is placed on the preform to distribute the resin throughout the preform uniformly. The porous layer with very low resistance is selected so that it gives the liquid resin an easy flow path to the preform.
15. The quality of liquid composite-molded parts depends on resin flow through the dry fiber preform.
a) True
b) False
View Answer
Explanation: The resin flow through the preforms affects fiber surface wetting and void formation. Incomplete mold filling, non-uniform resin distribution, dry spots, low degree and non-uniform cure are some of the problems associated with poor resin flow through preform.
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