Fabrication Of Glass Fibre Reinforced Polymers
Mechanical strength is determined by the amount and arrangement of the glass fibre reinforcement. The more material the stronger it will be and the arrangement will determine the strength in a given direction. Fibre moving in multiple directions will give the material stronger yield strength in more given directions. The formulation of the resin system adheres to the chemical, electrical and thermal performance of the material. The moulding process of the product is determined by production requirements and complexity of part. The truck bonnet is a large size and a complex shape, which needs a mould with various curves and corners. Reinforcement, resin system and processing method will be determined from these factors presented.
Glass Fibre Reinforced Polymers (GFRP) have “elevated specific strength and high specific stiffness”, which gives it good mechanical properties. There are different types of reinforcements, in this case glass-fibres, to choose from when making a GFRP piece. Each has different values of mechanical properties but “E-glass is the most commonly used fibre reinforcement. It is strong, has good heat resistance, and high electrical properties. ” This makes it a great candidate for making GFRP for a truck bonnet among other aspects. A work was done to examine the different mechanical properties of 5 GFRP composites. Each composite had different weight proportions by alternating the Glass fibre. Composite A had 15 wt. %, B 20 wt. %, C 25 wt. %, D 30 wt. % and E 35 wt. %. Furthermore, composite C with 25 wt. % in glass fibre has the highest mechanical properties out of all the composites. As can be seen from the graphs, through testing each composite, the values go up and then after composite C at the peak of the graph the values start declining. In each category composite C has the greatest value making it superior to the other combinations, establishing that 25 wt% fibre is the combination to used when regarding resin and glass fibre percentages. Here are the values of the different Mechanical properties of GFRP.
GFRP composites A, B, C, D and E were all tested for their Mechanical properties. Each composite contains different values but are all roughly the same. What can be noted from these observations is that GFRP is very versatile and functional. It has very high compressive and flexural strength. Which means it can under-go a strong amount of compression before failure and also resist deformation under load. The tensile strength is also fairly high which gives it protection from breaking under tension. The HB Hardness levels demonstrate the material being able to resist plastic deformation due to its hardness either by penetration or indentation. This helps prevent the material from breaking.
Different aspects of the design and process affect the overall cost of the fabrication of a GFRP truck bonnet. Matters such as reinforcement, matrix, combination aids, labour costs and machine costs all play a roll associating with the composites cost as a whole. The main considerable cost being the reinforcement material, which in this case is the glass-fibre. E-glass as the reinforcement material is the ideal choice as it obtains great mechanical properties for a reasonable cost when compared with other alternatives which are higher in cost. The most important aspect of the process is the matrix, which is the resin in this circumstance, as it determines and may reduce other costs in the process without being the major cost in itself. Thermosetting plastics and or polymers of polyesters allow for a highly flexible design and offer near effortless handling and manipulation with a low cost resulting in a cost effective solution as labour and machining costs would lower due to these factors. Moreover they have a “balance of good mechanical, chemical and electrical properties.”
Additionally the moulding method of GFRP can contribute to the lessening of labour and machining cost for the reason that some methods accommodate more to these factors. Spray-up is a great way to cut costs as it provides the advantages of “low cost tooling. ” It also offers simplicity in fitting the mould and greater shape complexities resulting in “virtually no part size limitations”. Its ability to make faster production helps decreased costs as “the process may be automated, ” diminishing labour hours. There is a vast distinction between the initial costs between GFRP and steel fabrications with steel being the cheaper of the two. Although this appears to be the case, in an overall cost, considering “the final delivered product, ” for GFRP composites “is often no more expensive than steel alternatives, ” and in the long term may become the cheaper alternatives due a “far lower whole-life maintenance costs. ” This is due to GFRP being resistant to corrosion and other damaging rust normally seen on aging steel parts. This weakens the material and it only ends up having a life-span of “a few years, ” whilst GFRP can last and is designed for life-span “of more than 20 years.”
Furthermore, there is an undeniable advantage of cost saving when picking GFRP over steel parts for a truck bonnet and that is the improved amount of fuel consumption. This is due to its lesser weight compared with steel. “An extra 100-lbs. in vehicle weight can reduce fuel economy by up to 2 percent, ”, which is a significant amount of cost saving is you take into account of how much trucks need to travel only a daily basis. For a production such as this GFRP for truck bonnets a suitable moulding method would be spray-up for it produces moderate quantities of mould at a time with low-cost tooling. The simplicity of spray-up allows for complex parts to be moulded with minimal difficulty due to its open mould. Moreover, this is seen as the glass-fibres can be added more in specific areas for a stronger finish and thickness. Reinforcement and catalysed resin are applied within a mould being spray over with a special spray gun. This helps ease the process and can develop an automated approach to the process. There can be manual labour her but also in the rolling out of entrapped air with a roller also wetting the fibre reinforcement creating a complete finish. Then there is a curing period where the composite hardens and is ready for use. This curing process is usually done at room temperature but can be accelerated if exposed to moderate heat. The finishing touch is in the trimming of the part, which can be made automated with a robotic trimmer to make sure the parts are consistent and completed within a shorter period of time.
The truck bonnet mould have a lot of complexities as can been seen by all the corners and curves involved with the mould created. This is due to the wheel arc creating space for the front wheel without any scraping. Other factors are covering the front and top of engine with accessibility for vents, headlights and other hardware.
