Saenz-Castillo, D. 1*, Rodriguez-Lence, F.1, Güemes, A.2

* Diego.Saenz@fidamc.es

1 FIDAMC; Getafe; Spain 2 ETSIAE (Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio), UPM; Madrid, Spain

INTRODUCTION & OBJECTIVES

DEFECTOLOGY IMPACT CHARACTERISATION

CONCLUSIONS

Composites materials (CFRP) with thermosetting matrix are highly used in the aeronautical industry. However, high-performance thermoplastic matrix have

emerged as a potential alternative due to high impact resistance, reprocesability and hardening without non-chemical reaction. This latest characteristic allows

the development of the in-situ consolidation of thermoplastic CFRP materials by Automatic Fiber Placement (AFP) technology without the need of any extra

consolidation process.

The aim of this Thesis is to characterise the impact of the defectology associated to different thermoplastic manufacturing processes on the performances of the

final structure. Besides, the laser-assisted AFP consolidation process will be monitored by optical fiber sensors to be able to monitor the key parameters of the

process such as temperature and strains, and to detect possible defects in real-time.

VOIDS AND FLAWS GENERATION

•Deviation from optimal temperature

•Deviation from optimal consolidation time

Defects as void or lack of consolidation are intended to be obtained with the

modification of the parameters from the optimal window process.

Monitoring and characterisation of manufacturing processes of

thermoplastic matrix materials

Deviation from consolidation cycle Void entrapment process

•High Air permeability in XY direction

•Sealant tape has been applied for perimeter

sealing

•Vacuum pathways are blocked

•Air is entrapped within the structure

•Different configurations have been performed

with the aim of getting different void content

Source: University of Delaware

IN-SITU PROCESS MONITORING

CHARACTERISATION

NDT

Physico-chemical

• Different sound

attenuation at

different

configurations

Mechanical testing

• Interlaminar porosity

• Intralaminar porosity

• Lack of consolidation

• IPSS testing

• High sensitive to

porosity matrix

• Fiber Bragg Gratting (FBG) sensors are built by radiating with laser

source into a optical fiber. To create a pattern, a phase mask is used

creating a Gratting with a wavelength:

𝐵=2𝑛𝑒

• FBG sensors are affected by several magnitudes. In this study, main

factor affecting FBG sensors are temperature and strains. The

equation ruling the sensor behaviour is:

Δ𝐵= 0[(∝+)Δ𝑇+(1−𝑝𝑒)Δ𝜀]=𝑘𝜀Δ𝜀+𝑘𝑇Δ𝑇

FBG SENSOR PRINCIPLES EXPERIMENTAL SET-UP ON-LINE MONITORING. DATA ACQUISITION

• Thermoplastic Automatic Fiber Placement (AFP) process is monitored. A specimen of 10 plies UD has been

consolidated. 2 tests have been carried out; with a single FBG sensor and with dual FBG sensor.

• Wavelength shift has been monitored during the process

• Decoupling of T and e has been carried out by two different

methods:

1. Temperature compensation by incorporing a thermocouple

2. Dual FBG sensor with second FBG being isollated from

external strains

Δ= 𝑘𝜀Δ𝜀+𝑘𝑇Δ𝑇

• Different values of void contents and ultrasonic attenuation have been achieved with the proposed manufacturing plan.

• Different values of mechanical properties (In-Plane Shear Strength) have been achieved corresponding to different temperature consolidation cycles.

• Further material characterisation need to be performed, including more physico-chemical and mechanical tests.

• FBG sensors have been integrated successfully in the thermoplastic AFP in-situ consolidation technology despite the high temperatures.

• Temperature and strain profiles have been decoupled by compensation of temperature.

• Artificial defectology must be implemented in the manufacturing process to develop a failure detection system with FBG sensors.

• 2 tests;

Single FBG

Dual FBG

• Thickness of the

specimen : 10 plies

• Polymer: PEEK

•Temp~400°C