Quantitative Nondestructive Evaluation of Automotive Glass Fiber Composites

Abstract

Thermographic, ultrasonic and acoustic emission nondestructive evalua tion (NDE) characterizations of flawed and unflawed SMC-R25, SMC-R50 and XMC-3 composites are conducted. For various flawed and unflawed states of the composites, these NDE characterizations are correlated with both flaw state and tensile fracture strength. Drilled-holes and V-notch flaws of various sizes result in correspondingly lower tensile strengths; however, in creases in fabrication temperature up to 177 °C and pressure up to 13.8 MPa, post-fabrication thermal exposure at 191 °C for up to 24 hours, water immer sion at 21 °C for up to 45 days and aluminum foil inclusions are found to have no significant effects on the tensile strength. For all three materials, the maximum number of thermographic color dif ferences is correlated linearly with the flaw size to specimen thickness ratio and with the tensile fracture stress for the drilled-holes and V-notch flaws. For all three materials, the ultrasonic through-thickness attenuation at 2 MHz is correlated linearly with the tensile fracture stress, independent of the material flaw state. And, for all three materials, the acoustic emission stress delay is correlated linearly with the tensile fracture stress, independent of the material flaw state. Thus, the NDE of fiber reinforced plastics (FRP) for structural integrity assessment is demonstrably feasible.