Vulcanization or curing process is a very important process in producing useful rubber products. The quality, performance as well as manufacturing cost of a rubber product are largely affected by the curing process. The curing process takes place when heat is transferred to the rubber compounds inside a heated mould. Curing of a thick article, such as a solid tire, often occurs under transient non-isothermal conditions. The temperature distribution in the rubber significantly affects the cure level distribution throughout the part, especially in a large rubber component. Therefore the ability to predict the distribution of cure level in a rubber part during curing is of great importance for improving the process efficiency and the quality of the final product. In this work, simulations of the curing process of a solid tire, consisting of three layers of different rubber compounds, were performed and the cure level distribution results were evaluated. The simulations are carried out using the commercial finite element software ABAQUS with the cure kinetics model for rubber implemented through the user subroutine UMATHT. The effects of the mold temperature and initial temperature of the solid tire on the cure level distribution and cure time were investigated.

The vulcanization or curing process begins in a heated mould to convert viscous uncured rubber materials into functional elastic ones. As the mechanical properties and service performances of the final products are greatly affected by the state of cure or cure level of rubbers, thus it is very crucial to use suitable time, pressure and temperature for the curing process to ensure that the desired quality of the final products are obtained. A computer program “RACE-CURE” written in standard FORTRAN code has been developed by our research team for the analysis of curing process of large rubber parts. The program is developed based on the incremental finite element formulation for three dimensional nonlinear transient heat transfer analysis coupled with cure kinetics. The RACE-CURE is tested for a test problem of curing of a large rubber block and results are compared to another two programs: ANSYS Polyflow v.14 and CFEM, a MATLAB© FEM program with capability to add curing kinetics, independently developed at our research group.

This work presents an initial study for hemp fibre produced in Thailand. The study focuses on the application of the filament winding technique in the production of hemp-epoxy composite tubes for a bicycle frame. The motivation is to produce hemp fibre composites from locally available resources in Thailand. For the initial trail, existing bicycle steel tubes were replaced by ±45° filament wound hemp-epoxy composites with thin aluminium inner layers. The mechanical properties of the hemp-epoxy composites were studied according to the ASTM standard. Two static load cases were chosen and considered for a 100 kg cyclist sitting on the saddle and pedalling while standing. The internal forces and moments were calculated for the frame and frame tubes. The stress and buckling analyses were performed using the finite element method for frame tubes considering the above loading cases. The finite element analysis shows that hemp-epoxy composite tubes with ±45° fibre orientation can be used as bicycle frame tubes and meet the design specifications under the considered static load conditions. The filament winding process was accomplished successfully at KMUTNB using an automated desktop filament winding machine.