# Experimental and Numerical Assessment of Fiber Orientation Effects in Biaxial Glass/Vinyl Ester Laminates

## TL;DR

This paper studies how fiber orientation affects the mechanical properties of a glass fiber composite material under different stress conditions.

## Contribution

The novelty lies in the detailed experimental and numerical analysis of fiber orientation effects in biaxial laminates under multiaxial stress.

## Key findings

- Maximum tensile strengths of 157.2 MPa at 90° and 125 MPa at 0° were observed.
- Minimum tensile strength of 59.6 MPa at 15° indicated fiber and shear failures.
- Off-axis orientations showed better impact energy absorption but fewer binding sites at 45°.

## Abstract

This study analyzes the mechanical behavior of a quasi-isotropic biaxial glass fiber–vinyl ester composite in a multiaxial stress condition and the effect of the orientation of the fibers. A ply structure was created through the process of vacuum infusion using six layers of biaxial fabric that were oriented to 15°. Tensile samples were isolated at 0, 15, 30, 45 and 90 degrees relative to the warp direction. It was found that strength and stiffness strongly depend on orientation, with maximum tensile strengths of 157.2 MPa at 90° and 125 MPa at 0°, and minimum tensile strengths 59.6 MPa at 15°, showing fiber and shear failures, respectively. MAT_124 underwent finite element analysis in LS-DYNA, and the results were excellent, with a difference of less than 1.5%. Three-point bending and Charpy impact tests indicated that flexural properties were lower at 15° and 90°, whereas off-axis orientations were generally better at impact energy absorption, although at 45°, binding sites were few and far between. The results have important implications for the design of laminates subjected to complicated loads.