The mechanical behaviour of a high performance polycaprolactone based polyurethane elastomer (PCL) up to large strain levels, cyclic loading and equibiaxial stress has been assessed. The PCL can be categorised as a rubber-like material, thus, showing nonlinear stress-strain behaviour. The materials elastic network is based on a high molecular weight PCL polyol which gives the material its elastomeric behaviour similar to polyurethanes. In this work, mechanical testing capturing the major features of the stress-strain curve under different loading conditions is performed. Both, uni-axial loading-unloading curves and bulge test are thoroughly studied through the addition of digital image correlation (DIC) to measure the strain field. Results show the presence of hysteresis and loading configuration dependence. Then, two well-known hyperelastic constitutive models, the Arruda-Boyce eight-chain and Bergström-Boyce, were fitted to the uni-axial monotonic and cyclic test data and compared to the bulge test experimental results through finite element analysis (FEA) in Abaqus.
Summary
The feasibility of using sugar‐cane bagasse as a reinforcement for natural fiber composites and the performance of these composites under fire conditions was investigated. Plies were manufactured using a process, which involved alkali‐treating bagasse, blending, pressing, and drying. Soaking durations of 30 minutes and 24 hours were compared. Composites were then made with these plies using a light resin transfer molding process. The composites were characterized and compared to a commercial hemp fabric using thermogravimetric analysis for thermal stability and char yield, isotropic hot disc method for thermal conductivity and specific heat capacity, and cone calorimeter for flammability. The investigation found that bagasse plies could be successfully used in composite manufacture, but posed a greater ignition hazard, and a comparable burning behavior hazard to the commercial product when tested at a radiant heat flux of 35 kW/m2. Thirty minutes treating resulted in a ply, which resulted in a char yield of 28%. Although in the composite form, there were no significant differences between all sample groups. With regards to ignition, the hemp composite had the latest time‐to‐ignition of 137 seconds. Comparison of the thermal properties to the ignition times showed that higher values of thermal properties resulted in later ignition times. The composite with the 30‐minute treated bagasse had a total heat release of 159 MJ/m2 and average heat release rate of 263 kW/m2, while the peak heat release rate was lower for the 24‐hour treated bagasse at 537 kW/m2. Overall, no significant differences in the two treatment durations were observed.
The fire performance of fibre-reinforced polypropylene (PP) was investigated with respect to fibre length and modification of the matrix. Fibre lengths of 3 mm, 12 mm, and continuous fibres were used as reinforcements. E-glass continuous fabrics were melt impregnated with PP and consolidated via compression moulding. E-glass fibre-reinforced PP pellets of 3 and 12 mm were compression moulded. Cone calorimetry tests with incident radiant fluxes of 20, 30 and 35 kW m−2 were used to investigate the fire properties of PP glass fibre composites. Results showed that continuous glass fibre reinforced PP exhibits the best fire performance at 20 kW m−2, while 3-mm fibre has the best performance at 35 kW m−2; 12-mm fibre-reinforced PP exhibitedthe lowest performance in comparison with 3-mm and continuous glass fibre reinforcement. Melic-anhydride (MA)-modified PP was found to increase the heat release rate (HRR) by up to 44% and time to ignition by up to 10% depending on the heat flux applied in comparison with unmodified PP. The glass fibre-reinforced composite made with MA-modified PP has 5–12% lower mean HRR and similar time to ignition in comparison with glass fibre composite made by unmodified PP. This suggests improved fibre adhesion plays a role of the fire performance of glass fibre-reinforced PP.
Summary
The interactions of Calcium carbonate (e.g., eggshell powder) and Lignin with ammonium polyphosphate (APP) when used as fire retardants were investigated. Three mixing ratios ‐ 1:3, 1:1, and 3:1, were used with natural fibre reinforced composites containing a hemp mat and an epoxy matrix manufactured using a light resin transfer moulding (L‐RTM) process. The thermal decomposition of the retardant mixtures and composites was investigated using thermogravimetric analysis (TGA). The findings showed that even though the decomposition reactions of APP with eggshell powder and lignin mixtures interacted and overlapped, the same interactions could not be seen in the composites. In the composite form while the residue was affected by the retardant, the decomposition reactions were driven primarily by the hemp and epoxy. Flammability of the composites was studied by testing to 20, 35, 50, and 75 kW/m2 with a cone calorimeter, and determining the critical heat flux. While the samples with eggshell powder had higher ignition times, the critical heat flux for ignition was 13 kW/m2 for all sample groups except for a ratio of 1:3 APP to eggshell powder, which was 14 kW/m2. The lowest burning rates (mass loss and heat release) occurred in composites containing only APP, however, the addition of eggshell powder or lignin at even a ratio of 3:1 APP to either provided a notable reduction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.