Andrade and Critical Time-to-Failure Laws in Fiber-Matrix Composites: Experiments and Model

TL;DR

This study investigates creep behavior and failure prediction in fiber-matrix composites through experiments and a simple load-sharing model, revealing power-law behaviors and correlations useful for early failure prediction.

Contribution

It introduces experimental evidence of power-law creep and failure laws in fiber composites and proposes a simple model linking primary creep to failure prediction.

Findings

Power-law relaxation in primary creep regime.

Power-law acceleration before failure in AE rates.

Correlation between primary creep characteristics and time to failure.

Abstract

We present creep experiments on fiber composite materials. Recorded strain rates and acoustic emission (AE) rates exhibit both a power law relaxation in the primary creep regime and a power-law acceleration before global failure. In particular, we observe time-to-failure power laws in the tertiary regime for acoustic emissions over four decades in time. We also discover correlations between some characteristics of the primary creep (exponent of the power-law and duration) and the time to failure of the samples. This result indicates that the tertiary regime is dependent on the relaxation and damage processes that occur in the primary regime and suggests a method of prediction of the time to failure based on the early time recording of the strain rate or AE rate. We consider a simple model of representative elements, interacting via democratic load sharing, with a large heterogeneity of strengths. Each element consists of a non-linear dashpot in parallel with a spring. This model recovers the experimental observations of the strain rate as a function of time.