Optimal design of carbon and glass reinforced hybrid composite pipes under flexural loading

This paper presents a study on the optimal design of carbon and glass reinforced hybrid composite pipes under flexural loading. The failure of composite pipes in three point bending was modelled numerically by Finite Element Analysis (FEA). Optimisation on hybrid composite pipes under flexural loading was conducted using non-dominated sorting GA-II (NSGA-II) with minimum cost and weight as the objective functions

Development of a process model for the vacuum assisted resin transfer molding simulation by the response surface method

The vacuum assisted resin transfer molding process (VARTM) offers many advantages over the traditional resin transfer molding such as lower tooling cost, room temperature processing. In the VARTM process, complete filling of the mold with adequate wetting of the fibrous preform is critical to the product quality. Computer simulation has become a powerful tool for liquid composite molding process design and optimization. However, in the VARTM process, since the presence of high permeable media, which has a much higher permeability than fiber, 3-D models are necessary and the extensive computation limits the usage of simulation in the process design and optimization.With the permeability, porosity, and thickness of the fiber preform and the RTM mold filling time as references, the dimensionless VARTM process variables and mold filling time are introduced in this paper. The significant process variables were identified by using the design of experiments (DOE). A quadratic regression model was developed by the RSM. The model was validated against the 3-D VARTM simulation and experiments. The results show that the accuracy is within 15% for most commonly used cases while the computation time saving is over 99%. The approach presented in this paper provides a general guideline for the VARTM process design and optimization. The process variables and flow media can be quickly chosen by using the developed regression model, which is extremely useful for composite part design in the early stage

Multi-objective optimal design of carbon and glass reinforced hybrid composites based on design rules

An optimisation study on the carbon and glass fibre reinforced hybrid composites in three-point bending is presented in this paper. For both unidirectional and multi-directional hybrid composites, the flexural properties were obtained by Finite Element Analysis (FEA)-based simulation. Several design rules were derived, and optimisation was done by applying these rules, with minimising the cost and weight being the objectives and the flexural strength being the constraint. The results from the design rule-based optimisation were compared with those from the non-dominated sorting GA-II (NSGA-II)

Dimensional variations of general curved composite parts

With the increasing demands of energy efficiency and environment protection, composite materials have become an important alternative for traditional materials. Composite materials offer many advantages over traditional materials including: low density, high strength, high stiffness to weight ratio, excellent durability, and design flexibility. Despite all these advantages, composite materials have not been as widely used as expected because of the complexity and cost of the manufacturing process. One of the main causes is associated with poor dimensional control. General curved composite parts are often used as the structural components in the composite industry. Due to the anisotropic material nature, process-induced dimensional variations make it difficult for tighttolerance control and limit the use of composites. This research aims to develop a practical approach for the design of general curved composite parts and assembly. First, the closed-form solution for the process-induced dimensional variations, which is commonly called spring-in, was derived. For a general curved composite part, a Structural Tree Method (STM) was developed to divide the curve into a number of pieces and calculate the dimensional variations sequentially. This method can be also applied to an assembly of composite parts. The approach was validated through a case study. The method presented in this paper provides a convenient and practical tool for the dimensional and tolerance analysis in the early design stage of general curved composite parts and assembly, which is extremely useful for the realization of affordable tight tolerance composites. It also provides the foundation of Integrated Product/Process Development (IPPD) and Design for Manufacturing/Assembly (DFM/DFA) for composites

Experimental study on strengthening of steel structures with fiber reinforced plastic

An experimental study on the strengthening of steel structures with FRP (Fiber Reinforced Plastic) is presented in this paper. Test coupons were prepared by applying FRP patches on both sides of steel coupons. Standard tensile tests were conducted to the test coupons. Two types of CFRP (Carbon Fiber Reinforced Plastic) and one type of GFRP (Glass Fiber Reinforced Plastic) were studied. The load and strain data were recorded, and the stiffness and strength were derived. The results show that CFRP provides better strengthening than GFRP, but there is no significant difference between PAN graphite/epoxy and pitch graphite/epoxy laminates