# Experimental Evaluation of Tensile Behavior and Hygrothermal Degradation of Glass Fiber Composites

## TL;DR

This paper studies how moisture and temperature affect the strength and durability of glass fiber composites used in structures.

## Contribution

The study provides new insights into hygrothermal degradation mechanisms in GFRP laminates through a combination of mechanical and thermal tests.

## Key findings

- Water immersion reduced tensile strength in diagonally cut GFRP specimens from 207 MPa to 63 MPa.
- Storage modulus decreased by 45% in 45° oriented specimens compared to principal directions.
- Aging increased the coefficient of thermal expansion below Tg from 205.6 to 291.65 µm/(m·°C).

## Abstract

Glass fiber-reinforced polymer (GFRP) composites are widely used in structural applications due to their high specific strength and durability; however, their mechanical performance strongly depends on fiber architecture and environmental exposure. This study evaluates the mechanical behavior and moisture-induced degradation of GFRP laminates through tensile tests, impact tests, dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA) performed on a bi-directional glass–epoxy GFRP laminate ([0°/90°]). Tensile tests revealed a maximum longitudinal strength of 369 MPa in dry specimens, while water immersion for up to 21 days led to a significant reduction in tensile strength, from 207 MPa to 63 MPa, in diagonally cut specimens. Impact tests conducted at 12 J showed larger displacements in specimens cut along directions not aligned with the fibers, indicating matrix-dominated behavior. Dynamic mechanical analysis demonstrated strong dependence of stiffness on fiber orientation, with storage modulus values decreasing by approximately 45% in 45° specimens compared with the principal directions, while the glass transition temperature remained within 59–62 °C. Thermomechanical analysis confirmed an increase in the coefficient of thermal expansion after aging, from 205.6 to 291.65 µm/(m·°C) below Tg. These results provide insights into the structure–property–environment relationships governing the durability of GFRP composites and support the optimization of their design for long-term polymer-based applications.