PULTRUSION OF POLYBENZOXAZINE RESIN MATRIX Z-PIN

The pultrusion of the polybenzoxazine resin matrix Z-pin is studied, because the Z-pin technology is an efficient reinforcement method for composites. Based on the curing characteristics acquired by differential scanning calorimeter（DSC） analysis, the suitable mould temperature for pultrusion is researched with the visual inspection and the Z-pin short beam shear test. The pull-out test is designed to evaluate the post oven temperature that can affect the combination between Z-pins and laminates. And then, the appropriate temperature for the post oven is obtained. Finally, micro photos are used to inspect the defects in Z-pins. The results show that when the resin is heated to 70°C, Z-pin pultrusion demands for viscosity are satisfied, and the shelf-life is about 4 h. With the mould temperature increasing to 140°C, the Z-pin short beam shear strength rises correspondingly and the cross section profile is the best. When the post oven temperature declines, the combination between Z-pins and laminates becomes stronger. However, pores appear in Z-pins unless the oven temperature increases to 200°C. Therefore, the optimum post oven temperature should be set at 200°C.

DEVELOPMENT OF BRAIDED－PULTRUSION PROCESS AND STRUCTURE－PROPERTY RELATIONSHIPS FOR TUBULAR COMPOSITES

In order to realize the potential of composite materials, it is imperative to develop a manufacturing process, to understand the microstructures, and to assess the structural performance of the composite. The braided-pultrusion process, which combines the pultrusion process with the braiding technology, has been developed by utilizing a novel resin impregnation device. The goal of the development is to achieve both costeffectiveness and performance of the composite. The tubular composites of diameter 5.3 mm have been produced using Kevlar 49 fiber and polyester resin. In order to assess the mechanical performance of the composites, an analytical method for predicting the elastic constants has been developed. The analysis includes the geometric model of a unit cell, coordinate transformation, and averaging of stiffness and compliance constants of the constituent materials. The analytic predictions compared favorably with experimental results.

Determination of the Optimal Speed of Pultrusion for Large-Sized Composite Rods

The paper describes a mathematical model of the stress-strain state of polymer composite materials in the pultrusion process of large-sized products. The influence of the pull speed on the stress-strain state of the products is investigated. To determine the maximum possible pull speed series of solutions at different pull speeds are obtained. Depending on the maximum strain in the cross section of the rod determined the optimal value of pulling speed.

Mechanical Behavior of Glass Fiber Reinforced Polymer Pultruded Composite Gratings

Well-designed and manufactured glass fiber reinforced polymer composite structures have several advantages over steel and conventional concrete structures such as high strength-to-weight ratio, good stiffness, good corrosion resistance and good damping capacity. In view of their higher cost however, their use is restricted to structures with smaller dimensions such as pedestrian walkways particularly where aggressive environmental conditions are encountered such as in chemical and water-treatment plants. The keys to success of these structures lie in the proper choice of the constituent materials, manufacturing method and knowledge of the behavior of the structure under the conditions encountered. Knowledge of the mechanical behavior is particularly important in this context. An investigation was therefore conducted by the authors, in partial fulfillment for the award of master of engineering science degree of Lamar University to the first author under the supervision of the second author [1], to study the response to loading of a glass fiber reinforced polyester composite structure made by the pultrusion process by a reputed manufacturer. The structure chosen for this study was a grating, the details of which are shown in the paper. This type of structure is particularly useful for walkways. The experimental part of the investigation consisted of subjecting the grating to three-point bend test under different loading conditions. The load-deflection curve for each case was obtained and interpreted. One grating was loaded up to failure and the fractured zone was examined using a scanning electron microscope to interpret the microscopic failure features. Simulation of the experimental work was carried out using an industry-standard FEM software to compare the deflection values. The results are presented and discussed in this paper.

Enhancement in Elastic Modulus of GFRP Bars by Material Hybridization

Fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated for last two decades and a number of FRP bars are commercially available. However, one of shortcomings of the existing FRP bars is its low elastic modulus, if glass fibers are used (i.e., GFRP). The main objective of this study using the concept of material hybridization is to develop a viable hybrid FRP bar for concrete structures, especially for marine and port con- crete structures. The purposes of hybridization are to increase the elastic modulus of GFRP bar with acceptable tensile strength. Two types of hybrid GFRP bar were considered in the development: GFRP crust with steel core and GFRP bar with steel wires dispersed over the cross-section. Using E-glass fibers and unsaturated polyester resins, the hybrid GFRP bar samples of 13 mm in diameter were pultruded and tested for tensile properties. The effect of hybridization on tensile properties of GFRP bars was evaluated by comparing the results of tensile test with those of non-hybrid GFRP bars. The results of this study indicated that the elastic modulus of the hybrid GFRP bar was increased by up to 270 percent by the material hybridization. The results of the test and the future recommendations are summarized in this paper. To ensure long-term durability of the hybrid GFRP bars in waterfront structure applications, the individual and combined effects of environmental conditions on hybrid GFRP rebar itself as well as on the interface between rebar and concrete should be accessed.

GFRP Poles for Traffic Signs and Signal Poles: A Case Study in Saudi Arabia

GFRP poles have been widely used as lighting poles but their use as traffic signs and signal poles is still under development. This paper highlights the literature review and case study of using GFRP poles for traffic signs and signal poles in the Eastern Province of Saudi Arabia. The case study details the design of poles, construction, maintenance and their performance. Traffic sign poles were manufactured using filament winding and signal poles using pultrusion process. AASHTO Standard “Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals” and ANSI 136.2. were used as materials specification and design for the pole. There is a need to develop dedicated design and construction guidelines to standardize the construction process. Further study about the crash resistance of GFRP poles at different speeds needs to be explored. In addition, the paper presents a high level comparison between the different materials like weight, safety, environmental degradation, strength, service life, durability in an aggressive environment, carbon footprint and economics.