An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites.

W J R Christian,K Atherton,E A Patterson,F A Diazdelao

doi:10.1098/rsos.180082

W J R Christian, K Atherton + Show 2 more

Open Access

https://doi.org/10.1098/rsos.180082

Copy DOI

Abstract

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect.

Highlights

Carbon-fibre composite materials are increasingly used for loadbearing aerospace structures as they exhibit high levels of specific strength along the fibre direction
This paper introduces a method to allow for the creation of localized areas of in-plane fibre waviness
As the curvature of the specimens was small, the residual strains in the specimens that caused the curvature were determined from the out-of-plane displacements [19]

Summary

Introduction

Carbon-fibre composite materials are increasingly used for loadbearing aerospace structures as they exhibit high levels of specific strength along the fibre direction. Well-established methods exist for creating typical defects in specimens and a substantial quantity of work has been undertaken on the effects of these defects and how they can be characterized. An example of this is impact damage, for which standardized methods of creating the damage have been developed [3], allowing impact-induced damage to be created using a repeatable method. If a repeatable technique existed to create fibre waviness defects in test coupons, the experimental characterization of waviness could become harmonized

Results

Discussion

Conclusion