Influence of the Unit Cell Parameters on the Thermomechanical Non-Symmetric In-Plane Shear Behavior of 2D Biaxial Braided Preform for Thermoplastic Biocomposites.

Wenqian Zhai,Peng Wang,Xavier Legrand,Damien Soulat

doi:10.3390/polym14061117

Abstract

The identification of thermomechanical in-plane shear behavior of preform is one of the most important factors to ensure the quality of the thermoplastic composites during the thermoforming process. In this present work, the non-symmetric in-plane shear behavior of flax/polypropylene 2D biaxial braided preform for thermoplastic biocomposites was characterized at elevated temperature chamber by using bias-extension test. Analytical models of a bias-extension test based on non-symmetric unit cell geometry for 2D biaxial braids were defined and applied; the thermo-condition-dependent experiments were conducted to study the temperature and displacement rate dependences. The influence of unit cell geometry parameters including braiding angle, tow waviness, and cover factor on the thermal in-plane shear behavior was deeply invested, experiments in both axial and transversal directions were performed for a complete study, and asymmetric scissor mechanisms for in-plane shear behavior were introduced and studied. Finally, a simulation of thermal impregnation distribution based on unit cell geometry was made to clarify the importance of the overall fiber volume fraction.

Highlights

Awareness of environmental and efficient issues in the last decades contributes to the important factors that encourage researchers to explore thermoplastic biocomposites [1–3]
The thermomechanical non-symmetric in-plane shear behavior of 2D biaxial braided preform is deeply investigated in this present study by applying the analytical model of extension based on unit cell geometry in an elevated temperature chamber
The thermocondition dependent experiments were preliminarily carried out and showed that higher temperature and lower displacement rate led to a lower in-plane shear moment

Summary

Introduction

Awareness of environmental and efficient issues in the last decades contributes to the important factors that encourage researchers to explore thermoplastic biocomposites [1–3]. In-plane shear of the preform is the predominant deformation mode to obtain double curved shapes [7,8]. The defects such as wrinkling, buckling, porosities, misalignment, and fiber fracture, etc. [9–11] can be issued from specific properties of the preform (fiber strength, textile reinforcement type and geometry) or from manufacturing parameters (tool loads, blank holder, temperature, etc.) [5]. The study on in-plane shear behavior is very important to improve the fundamental understanding of thermoforming, to provide better notice for reinforcement design and manufacturing condition decision, to avoid the defects formation

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