Coupled Hydro-Mechanical Aging Of Short Flax Fiber Reinforced Composites

TL;DR

This study investigates how combined environmental aging factors like temperature, moisture, and mechanical stress affect the mechanical properties of flax/poly(lactic acid) biocomposites, revealing synergistic degradation effects and fiber benefits.

Contribution

It introduces a novel testing setup for in-situ measurements of coupled aging effects on biodegradable flax fiber composites, highlighting the impact of combined environmental factors.

Findings

Aging temperature in wet conditions reduces elastic properties, especially at higher fiber contents.

Mechanical loading with water immersion causes a significant synergistic loss of stiffness.

Fibers delay environmental stress cracking and extend failure time.

Abstract

One of the challenges in the widespread use of biocomposites for engineering applications is the influence of environmental conditions on their mechanical properties, particularly for a combination of aging factors such as temperature, moisture, and mechanical stresses. Thus, the purpose of this paper is to study the influence of coupled aging factors by focusing on a 100% bio-based and biodegradable composites made of flax/poly(lactic acid) with several fiber contents. The development of a specific testing setup enabled continuous in-situ measurements and allowed comparing the effects of combined aging factors to those of uncombined aging factors. It was confirmed that the aging temperature in wet conditions led to a loss of elastic properties, especially for higher fiber fractions. While creep tests in dry conditions resulted in little decrease of elastic properties, it was observed that mechanical loading of the materials combined with water immersion resulted in a strong synergistic effect on the loss of stiffness. Finally, the presence of fibers reduced environmental stress cracking mechanisms and increased the time to failure.