1 Composites: basics and terminologyJohn Summerscales CAN-LHR 27 Sep 15 LGW-HKG 19 Sep 17 https://m.planespotters.net/photo/623175/ https://www.planespotters.net/photo/781126/

2 Reading for a degree Each lecture has: PowerPoint slides on extranetthese need JS “soundtrack” (i.e. lectures) individual lecture webpages on extranet also read these to reinforce your learning … and to really understand the topic follow up the references and/or review papers

3 Support materials http://www.fose1.plymouth.ac.uk/sme/mats3472 3

4 Structure of module MATS347one lecturer John Summerscales (JS) two themes materials selection and characterisation manufacturing processes assessed by one coursework report + one 3h examination Complemented by MATS348 (next term)t by module MATS348 final report

5 Support materials http://www.fose1.plymouth.ac.uk/sme/mats232Lecture & practical schedule Review papers Free e-books Subject index

6 Support materials for modulehome page on Extranet BSc MATS232: https://www.fose1.plymouth.ac.uk/sme/mats232/ BEng/MEng MATS347: https://www.fose1.plymouth.ac.uk/sme/mats347/ MATS347 lectures, notes and PowerPoint: https://www.fose1.plymouth.ac.uk/sme/mats347/PowerPoint/ Schedule on MooDLE home page case studies https://www.fose1.plymouth.ac.uk/sme/composites/marine.htm home page also includes: subject index map of local composites companies links to Library Reading Lists and many other useful resources ;-) see MooDLE student portal for assessments

7 LinkedIn professional networking site composites graduates from PUconnections for placement & employment British Composites Society other composites groups

8 Practical manufacture and test of a composite plateattendance at Health and Safety lecture is an essential prerequisite for coursework list of attendees circulated for signature if your name is not on the list, you will not be allowed to do the practical if you do not do the practical you will fail the coursework element and hence the module.

9 Civil and structural engineeringBridges Rehabilitation Enhanced carrying capacity of offshore rigs Repairs to LUL tunnels, plus bridges & pipework Cladding (~30 years) Mondial/Montedison House Buildings (not so) temporary structures

10 Outline of this lectureanisotropy fibre volume fraction (Vf) basic rule-of-mixtures glass transition temperature (Tg) crystalline melting point (Tm) stacking sequence notation

11 Anisotropy Degree of anisotropy Principal axes Properties ExampleIsotropic Orthogonal Constant regardless of direction Metals Square symmetric Two different principal axes Unidirectional fibres or woven cloth Orthotropic Three different principal axes Unidirectional weave with light weft Anisotropic Any angle Constant relative to axes Filament wound tube or many crystals Aeolotropic May change with position Timber

12 Fibre volume fraction (Vf)n = the number of layers AF = the areal weight of the fabric ρf = density of the fibre, and t = the thickness of the laminate.

13 Areal weight of fabric (AF)For a balanced fabric, the parameters are: Nf = number of filaments per tow NT = number of tows in unit width of fabric rf = radius of the fibre cross-section ρf = density of the fibre crimp increases areal weight by ~1% at 10˚, 3% at 20˚ or 6.5% at 30˚ maximum crimp angle.

14 Basic rule-of-mixtures 1Elastic properties (e.g. density or modulus) of composite calculated by rule-of-mixtures EC = κ . ηd . ηL . ηO . Vf . Ef + Vm . Em if the first term of the equation is large, the second term can be neglected

15 Basic rule-of-mixtures 2aThe parameters are: EX = modulus of component x Vx = volume fraction of component x subscripts (x) are c, f and m for composite, fibre and matrix respectively

16 Basic rule-of-mixtures 2bκ = fibre area correction factor* ηd = fibre “diameter” distribution factor* ηL = fibre length distribution factor ηO = fibre orientation distribution factor * these two factors are set to unity for man-made fibres (but see lecture MATS347A9 on natural fibres)

17 Basic rule-of-mixtures 3ηL = fibre length distribution factor 1 for continuous fibres fractional for long fibres 0 if fibre below a “critical length”

18 Basic rule-of-mixtures 4ηO = fibre orientation distribution factor a weighted function of fibre alignment, essentially cos4θ: 1 for unidirectional 1/2 for biaxial aligned with the stress 3/8 for random in-plane 1/4 for biaxial fabric on the bias angle

19 Basic rule-of-mixtures 5Vf = fibre volume fraction for random for fabrics for unidirectional consolidation pressure: no pressure gives the lower value Vf increases with pressure

20 Basic rule-of-mixtures 6figures below are lowest values i.e. for standard fibres Ef = elastic modulus of fibre glass = ~70 GPa (equivalent to aluminium) aramid = ~140 GPa carbon = ~210 GPa (equivalent to steel)

21 Transition temperatures in ascending orderTg = glass transition temperature Tc = peak crystallisation temperature Tm = crystalline melting point typically Tm = Tg + 200±50°C nb: no melting point in amorphous materials Tv = topology freezing transition temperature in vitrimers (viscosity = 1012 Pa s) Tp = processing temperature typically Tp = Tm + ~30°C for “semi”-crystalline polymers Tg follows cure temperature in thermosets Td = degradation/decomposition temperature may limit Tp (especially for PVC)

22 Glass transition temperature (Tg)Temperature at which segmental motion of the chain is frozen out below Tg polymer is elastic/brittle above Tg polymer is viscoelastic/tough more rigorous than heat distortion temperature Tg for thermoplastics = Tm - ~200°C Tg for thermosets follows cure temp.

23 Crystalline melting point (Tm)all polymers have a Tg only some polymers have a Tm they must be able to form crystals normally a regular repeating structure rarely 100% crystalline polymers may degrade before melting usually the case for thermoset

24 Composites How fibres can be arranged in order of increasing stiffness and strength: 3-D random e.g. injection moulding grades. planar random e.g. moulding compounds, chop strand mat, random swirl. quasi-isotropic (QI) e.g. continuous fibres oriented at 0°/-45°/90°/+45° or 0°/60°/120°. bidirectional e.g. woven fabrics or cross-plied UD laminates at 0 °/90 °. unidirectional (UD) e.g. pultrusions and aligned monolithic fibre composites.

25 Four types of fibre-reinforced compositemonolithic (material) all layers aligned parallel laminate (structure - see next slides) orientation changes between layers hybrid (structure – MATS347 lecture A6) more than one type of fibre (e.g. carbon/glass) sandwich (structure – MATS347 A10) composite skins and lightweight core

26 Laminate stacking sequence notationtypical laminate stacking sequence is: [0º/+45º/-45º/90º]ns where the subscripts are: n is the number of repeats of the sequence Q indicates antisymmetric laminate s means the laminate is symmetric T is the total number of plies overbar denotes that the laminate is symmetric about the mid-plane of the ply Thus for n = 2 above, the sequence will be: 0º/+45º/-45º/90º/0º/+45º/-45º/90º*90º/-45º/+45º/0º/90º/-45º/+45º/0º with * denoting the line of symmetry.

27 I-beam vs stacking sequenceBeam stiffness reduces from left to right: Laminated composite plate: 0° layer or 90° layer Equivalent beam: high EI vs low EI segments

28 Formative assignment (research–informed teaching/RIT)identify a laminate analysis package https://www.fose1.plymouth.ac.uk/sme/mats347/software.htm#laminate Autodesk Helius Composite software was the choice of last years’ students use it to determine the flexural stiffness of a hybrid beam UD aramid interleaved with woven glass the flexural stiffness of a sandwich panel bias-angle carbon fibre skins on a polymer foam core use rule of mixtures to calculate the tensile stiffness of the above beams consider why the numbers differ you will need this skill for the summative coursework assignment

29 Key points of this lectureresources on Student Portal and Extranet anisotropy fibre volume fraction (Vf) basic rule-of-mixtures glass transition temperature (Tg) crystalline melting point (Tm) stacking sequence notation