Effect of thermal gradient on interfacial behavior of hybrid fiber reinforced polypropylene composites fabricated by injection overmolding technique

Abstract

Hybrid fiber reinforced thermoplastic composites, fabricated by overmolding technique, are a novel class of lightweight components that benefit from the high mechanical performance of continuous fiber reinforced thermoplastics (CFRT) as well as geometric complexity because of short fiber reinforced thermoplastics (SFRT) composites architecture. The heterogonous interface between CFRT and SFRT in the hybrid structure was generated when SFRT was injected on CFRT surface during overmolding processing. However, the unmatched thermal properties between SFRT and CFRT may cause the poor adhesion at the interface due to the variation of temperature. In this article, how the thermal gradient affects the interfacial properties of hybrid structures is investigated through numerical and experimental methods. The results obtained from the molecular dynamics simulation demonstrate that decreasing thermal gradient can accelerate the molecular diffusion across the interface. Thus, at lower thermal gradient, the gap at interface is gradually disappeared. The results of the interfacial strength estimated by tensile lap shear test method show that the interfacial shear strength is greatly improved by decreasing thermal gradient because of higher crystallinity and bigger spherulite size of PP matrix at interface. In addition, the fracture mechanism of hybrid structure is observed to evolve with thermal gradient.

Effect of plasma treatment parameters on the interfacial joining strength of overmolded hybrid fiber reinforced thermoplastic composites

“…Sketch map of the special fixture and test sample are shown in Figure 2, as reported in our previous study. 36 Five samples were repeated for each group. The calculation formula of interfacial shear strength τ is as follows:…”

Selective Reinforcement of Joining Interface Using Nanofibers in Single-Lap Joints of Thermoplastic Composites Fabricated by the Injection Overmolding Process: Creep Deformation Behaviour

“…However, the resin temperature was lower than the cylinder temperature by approximately 10°C. The interface temperature (𝑇𝑇 𝑖𝑖 ) is predicted by the following equation [17]:…”

“…The welding mechanisms are described by (i) intimate contact development by providing the pressure and (ii) interdiffusion of polymer chains across the interface by heat transfer [9]. Furthermore, the crystalline structure of semicrystalline polymers, such as polypropylene (PP), polyamide (PA) and polyether ether ketone (PEEK), strongly depends on the temperature-related processing parameters during conventional injection molding [10]. Thus, the joining strength of the overmolded hybrid composite parts is controlled by the crystalline state and molding conditions.…”

Enhancement of interfacial strength of overmolded hybrid structures of short fiber reinforced polyamide 6 on continuous fiber reinforced epoxy composites under various surface pretreatments

“…One of the most effective approaches is to reduce the vehicle weight. [1][2][3] It is reported that every 10% of the weight decrease in a vehicle would reduce 7% of fuel consumptions. 2 Multi-material structure design by joining different light materials (e.g., fiber reinforced polymer composites and metals) provides a great lightweight potential for automotive area, which combines the individual advantages of these materials into a hybrid structure with structural performance that is not present in either of two constituent materials independently.…”