25. dynamic fracture behavior of polymeric materials

Department: Structural Engineering
Research Institute Affiliation: Agile - CaliBaja Center for Resilient Materials & Systems
Faculty Advisor(s): Veronica Eliasson

Primary Student
Name: Rodrigo Enrique Chavez Morales
Email: rchavezm@ucsd.edu
Phone: 785-979-7102
Grad Year: 2020

Abstract
In recent years fiber reinforced polymers have become popular materials in the construction of naval and aerospace vessels. These vessels tend to often be in harsh environmental conditions that can have a negative impact on their material properties after prolonged exposure. Thus, a study on the impact of water content and high humidity on the dynamic fracture behavior of polymeric materials is undertaken. A set of experiments was performed to assess the dynamic fracture behavior of Poly(Methyl Methacrylate) (PMMA), vinyl ester neat resin and carbon-fiber/vinyl ester (CFVE) composite. Edge-on impact experiments were performed on these samples by using a projectile launched from a gas gun. The impact generated a stress pulses that would initiate mode I fracture. The specimens were conditioned in different environments, including dry specimens, specimens exposed to different relative humidity environments, and distilled water saturated specimens. To gather data from the experiments the method of transmitted caustics and digital image correlation (DIC) were used. The experiments allowed for the calculation for the mode I stress intensity factor (SIF) of each sample when subjected to the stress pulses. It was observed that the fracture toughness of PMMA and neat vinyl ester had a negligible sensitivity to water content at strain rates on the order of 10^2 s-1. Additionally, the value for the mode-I critical SIF agreed with values previously reported. However, the fracture toughness of CFVE showed a significant sensitivity to water content, with its fracture toughness deteriorating approximately 30% after being submerged in water for 43 days. The deterioration observed in CFVE was attributed to debonding between the matrix and fibers.

Industry Application Area(s)
Aerospace, Defense, Security | Civil/Structural Engineering | Materials

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