Glass Fiber Reinforced Polymer Specimens Research Articles

STRENGTH PREDICTION OF DIFFERENT ORIENTATION UNIDIRECTIONAL GLASS FIBER LAP JOINTS

Composite materials have made way to various fields, including aerospace structures, underwater vehicles, automobiles and robot systems. Due to the high strength to weight ratio of composites, they serve as a suitable alternative to metals, therefore making the need for a reliable database of structural design more important. Most of the modern civilian and military aircraft use composite materials for their primary structural components (in addition to metals). One of the key areas in composite structural design involves the tensile strength of joints. In the present work, the lap joints fabricated from different orientations of GFRP (Glass fiber reinforced polymer) specimens are subjected to tensile test. The effect of fibre orientation on the tensile strength of lap joint is investigated both experimentally and computationally using conventional software package. The experimental results are compared with FEA using conventional software package ANSYS.

Multi-scale modeling of time-dependent response of smart sandwich constructions

Polymer and polymer based composite structures exhibit time-dependent response, leading to their being described as viscoelastic bodies. The rate of creep (or stress relaxation) in viscoelastic bodies increases with increasing the temperature of the bodies. In this study, we are interested in analyzing the time-dependent response of smart sandwich composites comprising of glass fiber reinforced polymer (GFRP) skins, polyurethane foam core, and lead zirconate titanate (PZT) wafers embedded in the GFRP skins. The PZT is used to monitor lifetime performance of sandwich composites. A multi-scale model is developed to integrate different constitutive models of the constituents in the sandwich structures. Quasi-static and creep tests are conducted for bulk epoxy, GFRP, polyurethane foam, and sandwich specimens under uniaxial tension and bending. The tests were done at room temperature and at 80 °C. The experimental data are used for material characterization and model verification. The multi-scale model that is developed can be used to understand the effect of different responses of the constituents on the overall time-dependent behavior of sandwich structures and examine the feasibility of using PZT wafers for monitoring lifetime performance of sandwich structures.

Strain-Rate Sensitivity of a Pultruded E-Glass/Polyester Composite

Structural analysis of composite structures subjected to dynamic loads requires detailed knowledge of the mechanical behavior of component materials under high strain-rates. This paper presents the results of tests to investigate the tensile dynamic behavior of a pultruded E-glass/polyester composite used in a steel-less blast protection barrier. The described activity is part of the Security of Airport Structures research project, focusing on structural protection of airport infrastructures against disruptive action. Modified Hopkinson bars and hydropneumatic machine devices were used to conduct strain-rate controlled tensile failure tests on glass fiber-reinforced polymer specimens. The results are discussed and then implemented within a viscoplasticity constitutive model and a strain-rate-dependent failure criterion in order to simulate the exhibited mechanical behavior.

Mixed-mode interlaminar fracture and damage characterization in woven fabric-reinforced glass/epoxy composite laminates at cryogenic temperatures using the finite element and improved test methods

The present research examines experimentally and analytically the mixed-mode interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. The mixed-mode bending (MMB) tests were performed with the improved test apparatus, at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). The energy release rates at the onset of delamination crack propagation were evaluated for the woven GFRP specimens using both beam theory and finite element analysis. The fracture surfaces were also examined to verify the fracture mechanisms. In addition, the initiation and growth of damage in the specimens were predicted by a damage analysis, and the damage effect on the mixed-mode interlaminar fracture properties at cryogenic temperatures was explored.