Manufacturing of Transparent Composites Using Vacuum Infusion Process

A novel optically-transparent glass fibre reinforced polymer matrix composite has been developed by infusing a clear epoxy resin system of matching refractive index into a conventional E-glass fabric preform. Transparent composites are manufactured using a low cost, environmentally friendly vacuum infusion process. Physical and mechanical tests have been conducted. Transparent composites manufactured using the modified vacuum infusion process had a fibre volume fraction of 40%. Tensile strength and tensile modulus of these composites were 374.9 MPa and 31.74 GPa respectively. the results indicate that the transparent composites possess good physical and mechanical properties. These transparent composites form a good base for developing new generation transparent armour systems

Synthesis and Performance Evaluation of Soybased Aliphatic Polyurethane Nanocomposites for Pultrusion

Polyurethane (PU) resin systems are generally characterized as aromatic and aliphatic. Aliphatic PU has lower mechanical properties than the aromatic resin system due to its chemical structure. The objective of the present work is to improve the mechanical properties of aliphatic resin system by exfoliating silicate nano particles. A pultrudable, soy-based, polyol-isocyanate aliphatic resin has been used as the base system. Nanocomposites were synthesized using the base resin and modified montmorillonite (MMT) clay. Modification of Na-MMT was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy analyses. Increase in the basal spacing of the nanoclay was observed by wide angle X-ray diffraction. The curing mechanism of soy-based PU resin with 1wt% of triethanol amine/methyl iodide exchanged MMT clay was studied using differential scanning calorimetry as well as FTIR. Tensile testing of the nanocomposites showed improved modulus when compared to the neat aliphatic resin system. Soy-based nanocomposites hold great promise as environmentally friendly and low cost materials for structural and automotive applications

Low Velocity Impact of Composites Manufactured Using Out-Of-Autoclave Process

Autoclaves have been commonly used to manufacture high performance composites for aerospace applications. However, high capital and tooling costs make these composites very expensive. Vacuum-bag-only cure out-of-autoclave (OOA) composite manufacturing process is potentially a lower-cost alternative to autoclave manufacturing. The OOA process does not require the positive pressure of an autoclave but still produces high quality composite parts. In the present study, high performance carbon/epoxy (MTM45-1/CF2412 carbon fabric) composite laminates have been manufactured using the OOA process. The low velocity impact response of the manufactured panels has been evaluated. Series of experiments based on Design of Experiments and Analysis of Variance (ANOVA) were designed and conducted to study the effect of varying the size of the test panel, lay-up configuration and thickness on the impact behavior of composites. Energy absorbed, peak force, contact duration, and maximum displacement were evaluated. Composites manufactured using OOA process had less than 0.25% void content. Impact energy versus time, contact force versus time, and contact force versus displacement plots were presented. Results showed that the amount of energy absorbed by the composites is significantly influenced by size, lay-up, thickness and the two-way interactions among the parameters. The peak force, contact duration and maximum displacement are mainly influenced by size, thickness and the interactions between size and thickness

Manufacturing and Mechanical Performance Evaluation of Resin-Infused Honeycomb Composites

In spite of numerous advantages of open-cell core sandwich composites, the applications have been limited due to the problems involved in manufacturing using low cost processes. Resin accumulation in the core is a major challenge in the fabrication of honeycomb sandwich panels using resin infusion techniques. Foam-filled cores and polymer film barriers are some of the methods used in the literature to address this issue. However, these techniques will increase the weight of the sandwich composites. In this study, honeycomb sandwich panels were manufactured using commercially available film adhesive and modified vacuum-assisted resin transfer molding process. The resin incursion into the core openings was investigated. No accumulation of resin was observed in the core. Flatwise tension, flatwise/edgewise compression, and three-point bending tests were conducted to evaluate the mechanical performance of the sandwich composites. The performance of sandwich panels during a low-velocity impact event was also evaluated. Results indicate that the vacuum-assisted resin transfer molding process can be successfully used to manufacture honeycomb composite sandwich structures using currently available barrier adhesive films

Manufacturing and Impact Characterization of Soy-Based Polyurethane Pultruded Composites

Composites have several advantages such as high corrosion resistance, high strength to weight ratio, and lower maintenance costs over conventional materials. the major cost drivers for composites are raw materials and manufacturing process. Automated manufacturing processes like pultrusion and low cost raw materials can significantly lower the cost of composites. Polyurethane (PU) resin systems are commonly used in the pultrusion industry as they have higher performance characteristics and manufacturing feasibility when compared to conventional resin systems such as polyester and vinyl ester. Manufacturing cost can be further decreased by the use of bio-based materials such as soy-based resin systems. in the present work, solid pultruded panels have been manufactured using the base PU and two soy-based PU resin systems. Pultruded panels were subjected to low velocity impact testing. Soy-based PU resin systems showed comparable properties to that of the base PU resin system and is a viable alternative to the conventional petroleum-based PU. POLYM. COMPOS

Elevated-Temperature Vacuum-Assisted Resin Transfer Molding Process for High Performance Aerospace Composites

Vacuum-assisted resin transfer molding (VARTM) is commonly used for general temperature applications (\u3c150°C) such as boat hulls and secondary aircraft structures. with growing demands for applications of composites in elevated temperature environments, significant cost savings can be achieved by employing the VARTM process. However, implementation of the VARTM process for fabricating elevated temperature composites presents unique challenges such as high porosity and low fiber volume contents. in the present work, a low cost and reliable VARTM process is developed to manufacture elevated temperature composites for aerospace applications. Modified single vacuum bagging infusion and double vacuum bagging infusion processes were evaluated. Details of the method to obtain high quality composite parts and the challenging issues related to the manufacturing process are presented. Density and fiber volume fraction testing of manufactured panels showed that high quality composite parts with void content less than 1% have been consistently manufactured. a property database of the resin system and the composites was developed. a three-dimensional mathematical model has also been developed for flow simulation and implemented in the ABAQUS finite element package code to predict the resin flow front during the infusion process and to optimize the flow parameters. the results of the present study indicate that aircraft grade composite parts with high fiber volume fractions can be manufactured using the developed elevated temperature VARTM process. © 2013 Society of Chemical Industry