A Novel Methodology to Characterize the Constitutive Behaviour of Polyethylene terephthalate for the Stretch Blow Moulding process

The stretch blow moulding (SBM) process is the main method for the mass production of PET containers. And understanding the constitutive behaviour of PET during this process is critical for designing the optimum product and process. However due to its nonlinear viscoelastic behaviour, the behaviour of PET is highly sensitive to its thermomechanical history making the task of modelling its constitutive behaviour complex. This means that the constitutive model will be useful only if it is known to be valid under the actual conditions of interest to the SBM process. The aim of this work was to develop a new material characterization method providing new data for the deformation behaviour of PET relevant to the SBM process. In order to achieve this goal, a reliable and robust characterization method was developed based on an instrumented stretch rod and a digital image correlation system to determine the stress-strain relationship of material in deforming preforms during free stretch-blow tests. The effect of preform temperature and air mass flow rate on the deformation behaviour of PET was also investigated.

Experimental Study of Interfacial Stress Distribution of Bonded-in BFRP Rod Glulam Joints Using Fibre Optic Sensors (FOS)

In this study, fibre optic sensors (FOS) were used to investigate the interfacial stress-strain behaviour of bonded-in basalt fibre reinforced polymer (BFRP) rods loaded into glulam members. Pull-out tests were conducted to examine the effect of bonded length and load-to-grain direction on the distribution of stress at the BFRP rod/adhesive zone. It was observed that the stress concentration at the loaded end of the BFRP rod of the samples was significantly the highest while the unloaded end showed the lowest. Increasing the bonded length at the same loading configuration resulted in a decrease in stress concentration at the loaded end. The stress concentration at the loaded end of the perpendicular to the grain samples was relatively higher than that of the corresponding parallel to the grain samples.