Glass fiber unsaturated composite impact resistance

Widely used FRP materials are often subjected to impact loads during use, such as the impact of the train when it is parked and stopped, and the collision deformation of the body when the car collides. FRP is widely used in the automotive industry due to its high strength and low price, especially for making bumpers and bodywork. According to experts, the impact resistance of these parts of automobiles is one of the important indicators to measure their mechanical properties. When a composite material is subjected to a low-energy impact during use, most of the cases do not have obvious visual damage. However, an invisible shallow surface layer is formed on the lamination surface, thereby forming a potential hazard. The presence of internal damage can cause Composite materials, a great loss in strength and stiffness. According to experts from China Unsaturated Resin Network, the low-energy impact damage mechanism and characteristics of composite laminates have been extensively studied. Giuseppe Sala and Dai Gil Lee have done a lot of work in this area. Some domestic researchers have also done similar work and achieved some results. There are many researches on the optimization design of composite plies, but there are not many studies on the effect of ply methods on the impact resistance of composites. According to experts, in order to design and produce safer and more stable FRP products, experts have conducted comparative analysis of low-energy impact performance for glass fiber reinforced unsaturated polyester resin composites using different lamination processes.

(3) Impact resistance test In the experiment, the weight of the drop hammer was kept constant at 5.7806 kg. According to experts, set the impact speed as required to obtain different drop heights. According to the law of conservation of energy, the instantaneous maximum impact kinetic energy of the drop hammer is:

In the formula, m is the mass of the drop hammer; Vi is the instantaneous speed of the drop hammer impact. The energy absorbed when the material is damaged is:

In the formula, Vf is the instantaneous maximum reversal speed after the falling hammer is rebounded by the board; it is the kinetic energy obtained by the falling hammer due to the elastic deformation energy released after the laminate is impacted.
During the impact, the impact load formula is:

In the formula, V(t) is the curve of speed versus time.
Test equipment: Dynatup92 material impact tester manufactured by INSTRON, USA.
Punch shape: bullet-like.
A 95mm x 95mm square test piece was placed on the support surface of the test bench and impacted on different layers of the sample. It is divided into 4 groups of 5 test pieces each, and the test data is taken as the average value of 5 samples. Each set of specimens selects the impact velocity v of the incident energy that can produce a large deformation of the specimen. According to experts, due to the operational error of each manual zero adjustment and the friction error generated during the impact of the machine itself, v causes a certain deviation based on the setting, and the range is between 0.8 and 0.9 m/s. Different impact loads - time and energy - time relationships are derived.

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