Effect Of Workers' Skill Level On The Quality Of Glass Fiber/Resin Composites By Hand Lay-up Method

With the rapid development of industry,glass fiber reinforced resin matrix composites are being widely used in automotive,electronics,marine,chemical,construction,aerospace and other industries due to their low price,fast forming and excellent mechanical properties.The rapid development of the glass fiber reinforced composites(be known as GFRP)industry has a positive effect on the development of its molding process.With the advantages of low production cost and products Processing are not limited by the size of the dimensions,hand lay-up which is the most traditional molding process,still occupy a large proportion in the molding process.However,the GFRP products by hand lay-up method are more dependent on the skill of the operators,and the quality of the GFRP products is unstable.Therefore,it is important to study the operator's skill to stabilize the quality of the GFRP products.This paper mainly studies the influence of the skill level of the operator on the quality of GFRP products by hand lay-up method.In order to explore the reasons,the first-line workers of different working ages were invited to produce laminates with the specified shape,size,thickness and number of glass fiber felt layers.To analyze the accuracy of the production,the thickness measurement at the complex corners of the structure was observed.On the other hand,the three-point bending test and the bending low-cycle fatigue test were used to investigate the difference of mechanical properties,and the interface characteristics were observed by scanning electron microscopy(SEM)to illustrate the influence of workers' skill level on the mechanical properties of GFRP composites.Firstly,the corner thickness of materials which were made of glass fiber reinforced and unsaturated resin matrix by three types of operators(experts,intermediaries,beginners)need to be measured in this paper.By analyzing the thickness of the embossing and concave corners of the composite laminate,the dimensional stability of these three types products was compared.The results manifested that: in the comparison of the corner thickness,the laminates made by the expert is great than materials made by the beginner,and the thickness of the laminate made by the middle is unstable;the results of thickness and the consistency of the two sides showed the laminates made by expert had the smallest degree of dispersion and the most stable,followed by the middles',and the beginners ‘products have the largest degree of dispersion and the most unstable.Secondly,the three-point bending test was carried out on the glass fiber reinforced unsaturated resin-based composite laminates made by three types of worker and the bending failure process was studied.In addition,the bending strength and flexural modulus of laminates made by different skill level workers were compared.The results showed that the bending-displacement curves of all kinds of composite laminates are basically similar,and their failure process is also basically same;when it comes to the comparison of the bending strength and the flexural modulus,the degree of dispersion of strength and flexural modulus of the composite laminates is gradually reduced as the working age of the operators increases,at the same time mechanical properties of the products tend to be more stable.Lastly,glass fiber reinforced unsaturated resin matrix composite laminates made by experts and beginners were subjected to low cycle bending fatigue(LCBF)test.55%,70% and 85% of bending failure load were selected as pre-load level,and the fracture morphology of the fracture surfaces before and after LCBF was observed by the scanning electron microscope(SEM).The results indicated that low cycle fatigue had been reduced the flexural strength and flexural modulus of the composites,and experts' laminates are more stable than beginners' no matter before or after bending low-cycle fatigue;The SEM interface observation showed that the interfacial properties of the fibers and resin in the laminates produced by the experts are better than those of the beginners;as the pre-load increases from 55% to 85%,the number of fibers that are drawn is increasing.At the same time,an interesting phenomenon was found in the experimental analysis of LCBF,as the preload increased,the laminates produced by the experts broke during the LCBF test,and the laminates made by the beginners did not break during the test,which needs further research and analysis.