Relationships between the glass fibre sizing composition and the surface quality of sheet moulding compounds (SMC) body panels

Abstract

The characteristics of thermosetting composite materials such as SMC are affected by the presence of reinforcements as a result of surface-matrix interactions. Surface treatments or sizings can significantly affect such interactions; hence the sizing selection may significantly affect SMC characteristics. The wetting properties of the unsaturated polyester matrix on glass fibres with different sizings have been studied by contact angle determination. In addition, the permeability of the glass fibres as well as their stiffness, the sizing solubility and swelling were also studied to understand the impregnation level of the glass fibres by the unsaturated polyester matrix before the curing reaction as a function of the sizing chemistry. The parameters that have been varied to determine the wetting and the adhesion properties provided by surface energies are the followings: (i) the sizing amount; (ii) the antistatic agent nature; (iii) the deposit method of this antistatic agent, and (iv) the film former nature. From these results in relation with the surface quality of corresponding moulded SMC panels, some of these glass fibres were selected. By using a statistical approach (principal components analysis (PCA)), it has been possible to conclude about the influence of the glass fibres characteristics on the surface quality. Correlations have also been established between the glass fibre characteristics, the material flow and the surface quality of the SMC panels.

Affecting glass fibre surfaces and composite properties by two stage sizing application

“…Interphases with gradual or monotonic change of mechanical properties and composition rather than homogeneous properties are highly expected, since in such case mechanical stresses can be efficiently transferred from matrix to reinforcement and the concentration of mechanical and thermomechanical stresses at this area can be greatly avoided [5]. Recent progresses in mechanical characterisation on interphases in combination with adhesion strength measurement and real composite mechanical tests indicated the presence of an interphase with mechanical property gradients leading to high mechanical properties [6][7][8][9][10][11]. As there is a steadily increasing interest in the use of thermoplastic composites in different fields, such as construction, automotive industries and aeronautic industries, in the field of GF reinforced thermoplastic composites various strategies have been developed in order to tailor the interphase characteristics, which mainly focused on the modification of GF surface or matrix, aiming at enhancing the GF-matrix adhesion strength, such as by enhancing GF-matrix compatibility, mechanical interlocking, and acid-base interaction [1][2][3][12][13][14].…”

“…For real reinforcements sized with the complete sizing formulation, it was proposed that silane coupling agent enriches on the sizing/GF interface, while the polymeric film former predominates on the sizing/ air interface, hence polymeric film former and polysiloxane network form an interpenetrating network (IPN) with gradual change of chemical composition from silane coupling agent dominated phase to polymeric film former enriched phase [29,35]. Literature addressing the formation of interphase dependence of sizing structure based on the complete sizing package is very limited [9][10][11]36]. In this study, silane coupling agent and polymeric film former were applied sequentially on as-spun GF at different stages, i.e.…”

Sheet molding compound characterization using spiral flow

“…On the other hand, glass carry and fiber orientation are also discussed in many publications as major material flow issues. [6][7][8][9] As previously mentioned, the heavy truck industry, being an industry where weight savings is critical, offers the largest potential for SMC growth. The trucking industry requires parts with high strength and stiffness, yet surface quality is important.…”

Thermoplastic Composites Reinforced with Textile Grids: Development of a Manufacturing Chain and Experimental Characterisation

“…In order to use engineering design guidelines, it has been shown that standard failure criteria in combination with adapted degradation models can be used to cover the non-linear material behaviour [26]. Other research groups have combined local endless fibre reinforcements with short fibres or long fibres [31][32][33][34] in order to increase both fibre volume content and mechanical properties instead of using grids.…”