The Effect of the Melt Viscosity and Impregnation of a Film on the Mechanical Properties of Thermoplastic Composites
Generally, to produce film-type thermoplastic composites with good mechanical properties, high-performance reinforcement films are used. In this case, films used as a matrix are difficult to impregnate into tow due to their high melt viscosity and high molecular weight. To solve the problem, in this paper, three polypropylene (PP) films with different melt viscosities were used separately to produce film-type thermoplastic composites. A film with a low melt viscosity was stacked so that tow was impregnated first and a film with a higher melt viscosity was then stacked to produce the composite. Four different composites were produced by regulating the pressure rising time. The thickness, density, fiber volume fraction (Vf), and void content (Vc) were analyzed to identify the physical properties and compare them in terms of film stacking types. The thermal properties were identified by using differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). The tensile property, flexural property, interlaminar shear strength (ILSS), and scanning electron microscopy (SEM) were performed to identify the mechanical properties. For the films with low molecular weight, impregnation could be completed fast but showed low strength. Additionally, the films with high molecular weight completed impregnation slowly but showed high strength. Therefore, appropriate films should be used considering the forming process time and their mechanical properties to produce film-type composites.
Effect of novel intumescent flame retardant on mechanical and flame retardant properties of continuous glass fibre reinforced polypropylene composites
Abstract In this study, the influence of a novel intumescent flame retardant (IFR) on the mode I interlaminar fracture toughness and flame retardant properties of continuous glass fibre reinforced polypropylene (CGF/PP) composites is presented. The novel IFR system that consists of ammonium polyphosphate/poly (ethanediamine-1, 3, 5 triazine-o-4-amion-2, 2, 6, 6- tetramentylniperidine) (APP/PETAT) was introduced into the CGF/PP unidirectional prepregs (UD) composites by hot-melt impregnation process. Double cantilever beam (DCB) tests were performed to evaluate the mode I interlaminar fracture toughness (GIC) by using modified beam theory (MBT). It was found from the experimental results that compared to the neat CGF/PP composite, the mode I fracture toughness initiation toughness (GIC init.) and propagation toughness (GIC prop.) of CGF/PP/12.5 wt% IFR composites were increased by an average of 99.7% and 119.11% respectively. Meanwhile, samples with 12.5 wt% IFR could self-extinguish with an oxygen concentration of 32.4% and exhibit lower fire spread speed in UL-94 test. Furthermore, the peak of heat release rate (PHRR), total heat release (THR), fire performance index (FPI), and mass loss rate (MLR) tests indicated that IFR could dramatically enhance the flame retardancy of the composites.
A computational analysis of the heating of glass mat thermoplastic (GMT) sheets by dual beam microwave sources
The use of dual beam microwaves to heat glass mat thermoplastic has been investigated numerically using a finite difference technique, known as the alternating difference implicit (ADI) method. The variation in thermophysical properties throughout the GMT has been accounted for using a table look-up procedure, which provides the appropriate thermophysical properties for the thermal conditions at each mesh point. The use of dual beam microwaves has been shown to significantly reduce the heating times under all geometric conditions, material variations, and glass loadings. Sheet thicknesses were varied from 1 to 12 mm, glass loadings from zero to 40 wt% polypropylene, polycarbonate and nylon were all simulated. The computations indicate a clear advantage in heating times when dual beam microwave heating sources are emplyed.