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Oh, The Places You’ll Go! A look at opportunities

available to engineering students and where they may take you.

Presented at: California Space Grant Consortium’s Undergraduate Engineering Seminar Series

University of California, San Diego October 15, 2014

by

Benjamin Martins

University of California, San Diego, La Jolla, CA 92093 [email protected]

October 15, 2014 2014 California Space Grant Fall Seminar Series 2

Overview

• Introduction

• CASL Undergraduate Research Assistant

• Nano-Reinforced Polymer Composites

• Composite UAV Design and Fabrication

• Active Load Redistribution

• Structural Health Monitoring and Prognosis

• Opportunity Available

• Tips for Success


Oh, the places you’ll go!


Take Home Messages

• Say Yes!

• Always do your best

• Take opportunity to develop secondary skills

• Stay patient

• Show initiative


Overview

• Introduction









F8 Project


F8 Project Cont.

0

200

400

600

800

1000

1200

1400

1600

0 50 100 150 200 250 300 350

Time [s]

Load

[N]

0.00E+00

2.00E+08

4.00E+08

6.00E+08

8.00E+08

1.00E+09

1.20E+09

1.40E+09

Cum

ulat

ive

Ener

gy [a

rb]


Detecting Damage in Composites


Detecting Damage in Composites Cont.


Lessons Learned

• Get into a research lab as quickly as you can

• Never think you’re above doing any job

• Always do your best

• You never know where it might lead


Overview

• Introduction








• Conclusions

Motivation

12

• Composite aircraft, rockets, and spacecraft have curved stringers, longerons, isogrid, etc…

• These elements experience combined interlaminar shear and tension

2014 California Space Grant Fall Seminar Series October 15, 2014

Introduction

13

• Composite laminates have outstanding fiber dominated properties

• Poor matrix dominated properties, interlaminar shear and tension

• Industry has tried 3-D stitching, brads, and z-pinning to improve interlaminar shear and tension

• Currently researchers are investigating the use of

carbon nanotubes (CNT) to improve the interlaminar shear strength in prepreg carbon/epoxy laminates 2014 California Space Grant Fall Seminar Series October 15, 2014

Introduction

14

• Vacuum Infused Resin Transfer Molding (V/RTM) and (RTM) are low-cost composite manufacturing approaches that are being used in the General Aviation (GA) industry and the aerospace industry

• Very little published research on the use of CNT’s to improve the interlaminar tension strength properties of V/RTM produced laminates

resin


• Current research investigates: • Improvements in interlaminar tension and shear properties in V/RTM

laminates using embedded CNT • CNT’s distributed using two different approaches:

• Metered spray deposition • CNT doped epoxy

• Interlaminar tension studied using modified ASTM standard

Introduction

15

P P P

circle ellipse

Interlaminar Tension

ASTM Methods 2014 California Space Grant Fall Seminar Series October 15, 2014

Specimen Design - Interlaminar Tension - Pure interlaminar

tension stress at apex of ellipse - No shear stress at this

location

- For more information, see: Velazquez, E., and Kosmatka, J.B., "Stresses in a Half-Elliptic Curved Beam Subjected to Transverse Tip Forces," 50th AIAA structures,

dynamics, and materials conference proceedings, Palm Springs, CA, 2009.

16

P

P


Specimen Manufacturing - Interlaminar Tension • Metered Spray Deposition Technique

- Carbon Nanotubes (CNTs) sonicated into isopropyl alcohol

- Half of each fabric ply sprayed with CNT/Alcohol Solution

- Laminate vacuum bagged and VARTM infused.

17 2014 California Space Grant Fall Seminar Series October 15, 2014

Specimen Manufacturing - Interlaminar Tension

- Cured semi-elliptical parts sectioned into control and reinforced specimens

- Strain gage placed on inner and outer surface of elliptical sections’ apex


Specimen Testing - Interlaminar Tension

- Quasi-static load to failure under displacement control

- Loaded at 0.10in/min.

- Strain monitored and recorded on inner and outer surface of elliptical sections apex

P

P


Results - Interlaminar Tension -Each CNT reinforced part compared to its corresponding control -Strength gains up to 18% -Strength heavily dependent on CNT concentration


Results - Interlaminar Tension - Interlaminar tensile failure moved

from mid-plane to outside reinforced region.

- Non-linear ILTS allows for targeted reinforcement

- Only treat a key number of plies

- No discernible impact on stiffness


Specimen Manufacturing - In-Plane Tensile and Shear • Metered Spray Deposition Technique

- In-plane property specimens cut from legs of semi-elliptical sections

Tension Specimens

Shear Specimens


Results - In-Plane Tensile and Shear

- Tensile coupons show modest gains (~5%) in Young’s moduli (~5%) and decrease in Poisson's ratio (~5.5%)

- Suggests CNTs stiffen in-plane response

- Shear coupons show large gains in Shear moduli (~40-50%%) and failure strain (~15%)

- Alternate test methods needed to validate shear moduli predictions



Lessons Learned

• Once you’ve made it to a research lab, always do you best • You never know when you may get your own project

• Never say never • Experiences you have may change your mind about your future


Overview

• Introduction








• Conclusions

UCSD AUVSI Introduction

October 15, 2014 26 2014 California Space Grant Fall Seminar Series

• Association for Unmanned Vehicle Systems International

• Student organization

• Multidisciplinary • Aerospace Engineering

• Mechanical Engineering

• Structural Engineering

• Electrical Engineering

• Computer Science and Engineering

• Physics

Mission


• Build an aircraft capable of: • Autonomous takeoff, navigation, and landing

• Auto-generate search paths through waypoints

• Live imagery

• Optical target recognition

• Remote message reconnaissance

• Remote payload deployment system

• Compete at a 3 day international student competition • Held each June at PAX Naval Air Station, MD

Sub-Teams


• Airframe: • Design, analysis and fabrication of aircraft and payload structures

• Mechatronics: • Design and fabrication of all mechanical systems (i.e. camera gimbal, power

bus)

• Embedded: • Development of the hardware architecture related to flight and payload

systems

• Software: • Design and implement code for autonomy, saliency, image recognition, data

downlink, etc…

Airframe: Falco-3


• All composite aircraft designed and fabricated by the team • ~10 foot wing span • GTOW of 55lbs

Airframe: Analysis


• Modeling with Solidworks and Catia • Structural analysis with FEMAP/NX NASTRAN and Patran/MSC

NASTRAN

Airframe: Fabrication


• Custom tooling made by the students • All composite layup

*disclaimer: with balsa stiffeners

Airframe: NextGen


• Andross • Fully carbon composite • Detachable payload • Improved aerodynamics

Image Recognition


Image Recognition


OCR


Image Processing


2013 Team


Lessons Learned


• Teamwork • Initiative • Diversity • Most noticed point on resume in job fairs! • Experience has helped with my research


Sterna Introduction

• Sterna is a UAS designed and built in the CASL

• Sterna v3 currently under design/fabrication

• All composite plane with multiple wing sets

• Used for research of in-flight SHM


Sterna Fabrication Progress

• Testing fuselage curing complete, ready for bonding

• Used to validate design


Overview

• Introduction








• Conclusions

Introduction

2014 California Space Grant Fall Seminar Series

Project Objectives • Build small UAS platform to allow for

experimentation in active control of segmented control surface (SCS) wings

• Utilize compact fiber optic strain sensing (cFOSS) system to measure in-flight structural response

• Develop models to predict aerodynamic loading and structural response

• Control in-flight wing deformations using real-time cFOSS data


Segmented Control Surfaces

• Current wing control surface configurations often produce unnecessary structural and aerodynamic loads

Flap

Aileron


• Current wing control surface configurations often produce unnecessary structural and aerodynamic loads

• SCS allow for higher resolution of aircraft control input

• SCS can be optimized over the flight envelope

• Key step to implementation of conformal control surfaces/ flexible wing concepts

cFOSS System • cFOSS system utilizes glass

optical fibers as strain sensors • Fiber Bragg gratings (FBG)

distributed along fiber • Laser interrogates fibers with

incident light • Straining fiber modifies FBG

spacing and hence reflected wavelength

• Capable of ~4000 strain measurements at ~50Hz


Aircraft (APV-3)

• Span: 12.33 ft • Dihedral: 2.5 ̊ along hinge line • Structure: Monocoque composite • Original control surfaces: Flap and aileron on each wing, split elevator, rudder

• Weight (without cFOSS system): ~35lbs • Weight (with cFOSS system): ~45lbs • Max gross takeoff weight: 55lbs • Fully autonomous capabilities (Piccolo II)


Fiber Optic Strain Sensors

• Continuous grated fiber with strain data measured every 0.5”

• 86ft of fiber provides over 2000 real-time strain measurements

• Fiber rosettes allow for shape, displacement, twist and principle strain calculations

Fiber Optic Strain Sensors


Segmented Control Surfaces

• Wings modified to include 22 independent control surface segments/servos per wing

• Servo uniformly spaced to produce 3” SCS from existing control surfaces


Complete System


Aerodynamic Analysis • Utilized Athena Vortex

Lattice (AVL) and XFLR5 programs

• Analytical model prepared for predicting aerodynamic loading of conventional and SCS configurations

• Aides in optimization of SCS configuration at various flight conditions


Structural Analysis

• Developed 32,000 element single wing model in FEMAP

• Wing loaded along quarter chord with load distributions predicted by AVL (40 nodes along span)

• Model solved with NX Nastran yielding strain and displacement predictions

• Used to study effects of SCS configuration on displacement and strain

Conventional Control Surface

Segmented Control Surface


Complete Systems Test


Complete Systems Test Video


Test Flights • Test flights conducted at

Dryden Flight Research Center small UAS work area

• Same Flight Patterns flown with (mimicked) conventional and segmented control surface configurations

• Circuits Flown – Steady Level Flight – Pitch Doublets – Roll Doublets – High g Steady Turn


Flight Results-Time History

Filtered Acceleration

vs. Time

Filtered Wing Tip Deflection

vs. Time


Flight Results-Time History

Filtered Acceleration and Wing Tip Deflection vs.

Time

Normalized Wing Tip

Deflection vs. Time

Control System On Control System Off


Flight Results-Conventional


Lessons Learned

• Self motivation • Team work • Building relationships



Overview

• Introduction








• Conclusions

Introduction- Motivation

• Inability to monitor damaged initiation and progression limits expanded use of composite

• Ability to detect and quantify

damage will be key to widespread acceptance of composite flight structures

2014 California Space Grant Fall Seminar Series October 15, 2014 60

Introduction- SHM


• Integrate an advanced sensor network to determine the structures current health and predict the future/remaining life

• Current CASL research

focuses on main wings

Defining Damage


Defining Damage

• Composites suffer from impact, overload and fatigue damage

• Failure by strength exceedance or stiffness degradation (flutter)

• The proposed system aims to detect:

• Fiber failure • Delamination • Matrix cracking • Bond strength

Operational and Environmental Variability

• Operational Variations include:

• Flight Velocity • Altitude • Maneuvering (V-n) • Loads • Changes in mass

• Environmental

Variations include: • Winds • Turbulence • Temperature

0 50 100 150 200 250 300-4

-3

-2

-1

0

1

2

3

4

5

6V-n and Gust Diagrams

Velocity, [ft/sec]Lo

ad F

acto

r (n)

Flaps UpFlaps DownGust

Lift = nW = 1/2ρV2SCL


Sensor System

• Extensive use of optical fiber strain sensors

• Supplement with a few

targeted traditional piezoceramics accelerometers

• High frequency modal measurements

• Secondary system to measure airspeed, gust loading, altitude, density and temperature


Modal Based Features

• Estimate modal parameters (natural frequencies, damping) to detect presence of damage

• Estimate mode shapes to detect damage location

• Mode shape derivatives (Curvature)

• Need accelerometers for higher modes

• Damage localization • Relies heavily on physical model

updating • Assumes linear behavior

• Nonlinearities can infer damage

Damage


Physics Based Modeling

• Need to develop vast database of structural models to develop relevant statistical models

• Strain and modal based method rely heavily on structural models • Use database to train SHM statistical algorithms

1st Bending Mode ∼7.5Hz


Supervised Machine Learning

• Building multiple wing sets allows for data to be collected from damaged and undamaged wing sets

• Heavily damaged wings cannot be flown so must be tested using static and dynamic ground test

• Supervised learning allows for damage detection, sizing, type and possibility of prognosis


On Going Work in SHM

• Current efforts in the CASL focus on composite beam testing


DWDM Sensor

FBGS Sensors

On Going Work in SHM- Test Setup

• Fiber optic strain gages bonded to beam

• Currently ~1200 gages • Strain information

recorded for static and dynamic loads


On Going Work in SHM- FEM

• Beam modeled in FEMAP • Information pulled from nodes

corresponding to strain gages locations on physical beam


Simulated Impact

• Simulate impact by reducing stiffness of elements by 10% in 0.25” radius


Simulated Fiber Breakage

• Simulate fiber breakage by deleting one 0.088”x0.088” element


Lessons Learned

Patience



Overview

• Introduction









Student Orgs

• Engineering Organizations with Project Teams at UCSD:

http://www.jacobsschool.ucsd.edu/student/student_involved/involved_org/


Internships

• Port Triton

• DECaF Job Fair

• Student Services Center • Go to resume/interview workshops

• Employer Website

• NASA OSSI - https://intern.nasa.gov/ossi/web/public/main/

• One stop for Internships, fellowships and scholarships with NASA


Research Labs

• Most professors on campus conduct research • If you’re interested in a class, do well, make yourself known to the

professor and then ask about the research they do

• Some opportunities are even paid!


Overview

• Introduction









Tips for Success

• Remember all opportunities are good opportunities • Doing something slightly interesting may lead to very interesting things

in the future

• Stay patient

• Show initiative

• Work hard/ Always do your best

• “You don’t know what you don’t know”

80

Acknowledgments

October 15, 2014

I would like to thank my mentors, - Dr. John Kosmatka, University of California, San Diego - Dr. Lance Richards, NASA AFRC/AERO Institute - Francisco Pena, NASA AFRC/AERO Institute And, Tehseen Lazzouni and Rebecca Howard from the California Space Grant Consortium As well as numerous people at NASA Armstrong who provided advice, guidance and support, including:

- Robert “Red” Jensen - Allen Parker - Dr. Oscar Murillo - Dr. Patrick Chan


81

Support

October 15, 2014

Funding for these project was provided by: - NASA Aeronautics Research Mission Directorate - NASA Aeronautics Academy, Dryden Flight Research Center - California Space Grant Consortium


82

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