Transparent Orthotropic Composites Materials By: Tiffany Di Petta Adviser: Professor Dahsin Liu

1. Transparent Orthotropic Composites Materials By: Tiffany Di Petta Adviser: Professor Dahsin Liu Problem Statement: Create a transparent composite that can be manufactured with a current industry process. Transparent composites will allow for nondestructive analysis of specimen with photoelasticity or visual conformation of internal damage. Experiment Setup: The setup only requires a white light source and a digital camera (Figure 1). Each specimen was placed in between the light source and the camera as shown. A digital picture was taken of each specimen. Software was used to determine the intensity at every pixel of the pictures. Camera Specimen Light Figure 1. Experiment setup Results: The intensity of each specimen has been graphed below (Figure 2). The intensity shown ranges from 0 to 1. A transparent specimen will have an intensity equal to 1 because 1 represents white light. An opaque specimen will have an intensity of 0 because 0 represents no light. From the graph the average intensity over a central region has been calculated and shown in Table 2. The epoxy with the highest intensity of the tested epoxies was the Devcon 2-ton. All the composite specimen were semi-transparent because none of them had a intensity equal to 1. Introduction: A composite is a structure consisting of distanced components. The composites that were manufactured were comprised of two components which were glass fiber and epoxy. In order to produce a transparent composite specimen, the index of refraction of the glass fiber and epoxy has to be the same. The indexes of refraction of epoxies are usually NOT measured in the industry. Therefore, many industry epoxies will be used to manufacture many composites and the transparency of each composite will then be measures. Table 2. Average intensity of the central region for each specimen Materials: Glass Fiber: The glass fiber used was unidirectional E-glass from JP Composites. The index of refraction of E-glass is standard at 1.548. Epoxies: Five transparent epoxies from multiple companies were used to create composites. The list of epoxies is below and the index of refraction of each is unknown. • Manufacturing Method: • Transparent Samples Process: • The specimen has six layers of unidirectional E-glass fiber oriented in a repetitive 0-90 configuration. Epoxy was injected between each layer and 25 lb/in2 load will be applied. • VARTM Process and it’s Limitation: • The final composites will be manufactured with the VARTM method, which stands for Vacuum Assisted Resin Transfer Molding. The VARTM method requires an epoxy with all of the following properties: • Low viscosity epoxy • Two part epoxy • Epoxy work life greater then 10 min • Epoxy curable at room temperature Table 1. The five epoxies used to manufacture composites with their work life and cure life Figure 2. Intensity reading over each specimen region Conclusion: The Devcon 2-ton epoxy produced the best composite with an average regional intensity of .68 so the composite is semi-transparent. The transparency is not sufficient for photoelastic analysis. However, the transparency is sufficient for visual analysis of the propagation of internal damage of specimen.