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​What is the reason for affecting the quality of FRP tanks?

Feb 16, 2019

Introduction to the reasons affecting the quality of FRP tanks

1. In the winding process of the thickening and reducing layer in the FRP tank winding process, appropriately increasing the number of fiber strands and reducing the number of winding layers is one of the measures to improve the production efficiency of the container. However, it should be considered in the application, and the production efficiency cannot be pursued blindly. After the number of fiber strands increases, the phenomenon of "overhead" at the intersection of the wound wire type and the tangent point of the pole hole will intensify. The pores are formed between the fibers of the overhead portion and the inner liner. When the container is pressurized, the aluminum lining can not be subjected to the pressure and will be squeezed into the overhead part, which seriously affects the fatigue performance of the container. After the number of fiber strands increases, the number of longitudinal winding layers decreases correspondingly, and the number of enveloping circle diameters also decreases, so that the fibers are not evenly distributed in the head, resulting in a decrease in head strength. Therefore, measures to increase shareholdings should be carefully adopted. Improper application can result in a decline in product quality.

2, the layer-by-layer decreasing tension system FRP winding container to obtain high strength is an important premise is to make each fiber to receive a uniform tension, that is, when the container is subjected to internal pressure, all fibers are simultaneously stressed. If the fibers are loose and tight, then all the fibers cannot be stressed at the same time during charging, which will affect the fiber strength. The tension also directly affects the gel content, specific gravity and porosity of the product. Irregular tension system will also cause wrinkles in the fiber, yielding the lining, etc., which will seriously affect the strength and fatigue properties of the container.

Winding tension should be reduced layer by layer. This is because the layer of fiber that is wound on the back is compressed and deformed together with the inner liner due to the tension, so that the inner layer fibers are loosened. If a constant tension system is adopted, the fibers on the container will be loose and tight, and the initial stress of the inner and outer fibers will be greatly different. When the container is pressurized, the fibers cannot be uniformly stressed at the same time. In severe cases, the inner layer fibers may be subjected to wrinkles, lining bubbling, deformation, and the like. This will greatly reduce the strength and fatigue properties of the container. After using the layer-by-layer tension system, although the fibers that are entangled still have a reducing effect on the fibers that are first entangled, because the tension is small, it is the same as the tension after the first layer is cut. Ensure that all wound layers have the same deformation and initial tension from the inside out. When the container is pressurized, the fibers can be stressed at the same time, so that the strength of the container is improved. Make fiber strength better.

3, the layered curing process system layered curing process is carried out in this way. A FRP shell of a certain thickness is formed on the lining to be solidified, cooled to room temperature, polished by the surface and then wound a second time. This is the same, until it is wrapped around the number of layers that meet the strength design requirements.

Glass steel can

The fact that thick-walled containers are lower than thin-walled containers has been theoretically confirmed. As the volume of the container increases, the pressure increases and the wall thickness increases. The difference in strength between the FRP thick-walled container and the thin-walled container. In addition to the reasons for mechanical analysis, there are the following points from the perspective of FRP container manufacturing:

1) As the thickness of the container increases, the internal and external mass non-uniformity increases; 2) As the wall thickness of the container increases and the number of wound layers increases, the winding tension of the fibers is required to be smaller and smaller, so that the initial tension of the fibers in the entire container is low. This will affect the deformability and strength of the container.

In order to effectively exert the fiber strength in thick-walled containers, layered curing is an effective technical approach. The layered solidified container appears to transform a thick-walled container into several thin-walled container assemblies that are tightly nested together. Under the action of internal pressure, they have the same deformation, withstand the same stress, without the constraint between layers, and can slide freely with each other. This gives full play to the superiority of the thin-walled container in terms of strength.

Since the container is solidified in several times, the position of the fiber in the container can be fixed in time, so that the fibers are not wrinkled and loosened, so that the resin is not lost between the layers, thereby improving the uniformity of the quality inside and outside the container.

4. Vacuum curing method FRP container is heated and solidified in a vacuum environment, which can increase the strength by more than 10%. Vacuum curing is one of the effective ways to improve the strength of the container. During the manufacturing process, some of the remaining solvents and other low molecular substances are not completely removed under normal pressure, and these remaining low molecular substances are attached to the resin! At the interface of the glass fiber, the strong adhesion of the resin to the glass fiber is hindered, thereby affecting the strength of the container. The vacuum curing method can make the low molecular weight volatilize more completely, and make the FRP more dense. Therefore, the strength of the container can be improved.


QuanZhou Neweco High Polymer Material Co.,Ltd.

Neweco is one of the leading unsaturated polyester resin manufacturers and  suppliers,widely used in automobiles, ships, rail transit, wind power  generation, pipe cans, heat and corrosion protection, building  materials, stone repair, sanitary ware, artificial stone and other  industries. Suitable for hand lay-up, spray, pultrusion, winding,  molding, vacuum introduction / RTM, casting and other molding processes. Neweco Resin is committed to excellence and focuses on the application  of composite materials to provide customers with comprehensive  solutions.

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