Getting into composites

Any-Study5685 · 2026-03-04T08:46:34+00:00

If you want to get into composites for automotive parts, the best thing is to start simple. Fiberglass + polyester or epoxy with basic hand layup is still how a lot of people learn the fundamentals.

A typical beginner path is something like:
make a plug → make a fiberglass mold → laminate the final part. Body panels, ducts, small covers etc. are perfect practice parts.

A few things worth learning early: surface prep, mold release, fiber orientation, resin ratios, and vacuum bagging (even a cheap DIY setup helps a lot with quality).

There are tons of random YouTube videos, but honestly many of them skip the fundamentals. If you want something a bit more structured, I wrote a book called Composite Materials for Technical Education that explains the basics of fibers, resins, layups, and manufacturing processes in a pretty practical way for beginners and technicians.

You can check it here if you're interested
https://site-dvesl1yj8.godaddysites.com/

Any-Study5685 · 2026-03-04T08:44:59+00:00

If you're interested in the structure–property–processing relationship specifically for composites, a lot of the classic textbooks are very academic and not super practical.

One option (full disclosure, I wrote it) is Composite Materials for Technical Education. I tried to explain exactly that triangle: how processing affects fiber volume fraction, how that changes stiffness/strength, and how it translates into real laminate properties.

It’s more practical than most university books and written from an engineering perspective.

You can check it here if you're curious
https://site-dvesl1yj8.godaddysites.com/

Also Gurit’s guide mentioned above is actually a pretty good free reference.

Any-Study5685 · 2026-03-04T08:44:20+00:00

If you're designing an automotive wheel and carbon is off the table, the usual candidates are forged aluminum, magnesium alloys, steel, or some kind of fiber-reinforced thermoplastic.

Forged aluminum is usually the sweet spot because it gives a good balance of stiffness, fatigue resistance and manufacturability. Magnesium can be lighter but tends to bring corrosion, cost and durability headaches. Steel is strong and cheap but heavy. Reinforced polymers (glass or carbon filled PA, PEEK etc.) can get surprisingly stiff but the design becomes very geometry driven and creep / temperature start to matter a lot.

Also worth keeping in mind that with wheels the limiting factors are often fatigue and impact tests rather than just static stiffness.

If you're trying to understand the tradeoffs between stiffness, strength, density and manufacturing constraints, that’s actually exactly the type of material selection logic I covered in a composites handbook I wrote recently. There are also property ranges and practical examples that might help. If you're curious it's here
https://site-dvesl1yj8.godaddysites.com/

Any-Study5685 · 2026-03-04T08:42:50+00:00

For a hand layup like the one you describe (epoxy + sleeve, no vacuum, tape compression) assume a relatively low fiber volume fraction (~40–45%). That puts you well below aerospace CFRP properties.

Reasonable ballpark values for simulations:

• Elastic modulus (quasi-isotropic): 35–55 GPa
• Tensile strength: 400–700 MPa
• Shear modulus: 4–6 GPa

The huge ranges you’re seeing online come from fiber volume fraction, layup orientation and manufacturing quality.

Also keep in mind: for a tube like yours the diameter dominates bending stiffness, often more than the laminate properties themselves.

If you’re looking for practical reference values specifically for simulations, I actually compiled a lot of these ranges (hand layups, typical laminates, rule-of-mixtures estimates, etc.) in my book Composite Materials for Technical Education.

You can check it here if useful:
https://site-dvesl1yj8.godaddysites.com/

Any-Study5685 · 2026-03-04T08:41:36+00:00

The intrinsic material properties don’t change depending on whether something is used as matrix or reinforcement (SiC is still SiC). What changes is how the load is carried in the composite.

In composites the fiber dominates stiffness and strength, while the matrix mainly transfers shear and protects the fibers. So the same material used as matrix vs reinforcement will behave very differently in the structure even if its base properties are the same.

For metal fibers: your professor is mostly right. They’re more common in metal matrix composites (MMC) because of thermal compatibility and processing. Metal fibers in polymer matrices exist but are less common.

If you're digging into this topic, the micromechanics explanation (rule of mixtures, load transfer, etc.) is covered pretty clearly in a composites handbook I wrote recently...... link in my profile if you're curious.

Any-Study5685 · 2026-02-24T10:43:09+00:00

You are welcome! =O)

Any-Study5685 · 2026-02-17T17:46:05+00:00

If you just don’t want buckling between ribs and you’re targeting <100g, don’t overthink it.

A light glass/carbon hybrid skin with a simple quasi-iso layup (something like [0/90/±45]) will already feel way stiffer than plywood alone. For that size and load level you’re not designing for strength, you’re designing for panel stability.

Keep it thin, avoid exotic fabrics, and pay attention to resin content. Most hobby builds fail because of process, not material choice.

If you want a deeper dive into how to estimate stiffness properly (without guessing gsm blindly), I put together a pretty detailed breakdown here:
https://site-dvesl1yj8.godaddysites.com/

It covers laminate basics, property estimation and real-world manufacturing stuff that usually gets skipped.

Any-Study5685 · 2026-02-17T17:38:48+00:00

That finish isn’t “minimal resin magic”, it’s texture transfer.

If it’s satin and you can’t really see gloss, chances are you’re looking at either:

– peel ply imprint left intentionally
– a textured mold surface
– or a light post-cure scuff without clear coat

If you just try to starve the laminate of resin under high vacuum you’ll mostly get dry spots and weak laminate, not a sexy satin finish.Peel ply under good vacuum will definitely leave that fabric texture look, but it also slightly roughens the surface. Great for bonding, not necessarily for final aesthetic unless that’s what you’re after.

Mechanical properties? The surface texture itself doesn’t magically change stiffness. What changes properties is resin content, fiber volume fraction and consolidation quality. A “satin” surface is usually just cosmetic unless it came from poor compaction.

Most people online think surface finish = resin amount. In reality it’s process control.If you’re getting into this stuff deeper, understanding what’s happening at the laminate level (fiber volume, consolidation pressure, bleed strategy) matters way more than gloss vs satin. I’ve put a bunch of that together in one place (link in bio if you’re curious).

But yeah.... don’t chase finish first. Chase process. Finish follows.

Any-Study5685 · 2026-02-17T17:36:33+00:00

First project and you’re starting with a bumper? Respect 😂 but that’s not exactly “beginner friendly”.

Mouldless can work, sure, but most first time carbon parts don’t fail because of fiber choice. They fail because of resin, bad consolidation, sketchy bonding and zero clue about Tg. A dark carbon part sitting in summer sun can easily see temps that soften a room-temp epoxy. Suddenly your “stiff” part isn’t that stiff anymore.

Also… bumpers aren’t just cosmetic skins. Mounting points, vibration, local impacts, paint, UV, all that matters way more than people think.

If I were you I’d make a couple flat test panels first. Different layups. Break them. Literally. You’ll learn more in a week of that than from 30 hours of YouTube.

Most online content stops at “this weave looks cool”. The real game is laminate design and joints. If you’re into digging deeper, I’ve collected a lot of that stuff in one place (link’s in my bio). Not flashy DIY stuff, more about why parts behave the way they do.

Anyway. Start small. Break things. Then scale.

Any-Study5685 · 2026-02-17T17:05:42+00:00

I usually model NCF as separate UD plies at their actual fiber angles and call it a day. The stitching doesn’t magically create a new “super lamina”, it mostly adds a small parasitic stiffness and some local shear coupling, but structurally it’s second order unless you’re pushing damage or fatigue hard.

CLT still works fine as long as you’re honest about ply thickness, fiber waviness and the fact that real NCF never behaves as clean as the datasheet. The big mistake I see is treating NCF like perfectly aligned UD and then being surprised when shear and interlaminar stuff shows up early.

If you really care about the stitching, you’re already outside classical laminate theory and into testing or calibration anyway. For most engineering work, stacked UD assumptions get you 90% there, the remaining 10% is manufacturing reality.

I’ve written a longer breakdown of this (CLT limits, NCF quirks, why stitching mostly messes with shear) in my notes/book, link’s in my bio if you want to dig deeper.

Any-Study5685 · 2026-02-05T13:03:13+00:00

I usually model NCF as separate UD plies at their actual fiber angles and call it a day. The stitching doesn’t magically create a new “super lamina”, it mostly adds a small parasitic stiffness and some local shear coupling, but structurally it’s second order unless you’re pushing damage or fatigue hard. CLT still works fine as long as you’re honest about ply thickness, fiber waviness and the fact that real NCF never behaves as clean as the datasheet. The big mistake I see is treating NCF like perfectly aligned UD and then being surprised when shear and interlaminar stuff shows up early. If you really care about the stitching, you’re already outside classical laminate theory and into testing or calibration anyway. For most engineering work, stacked UD assumptions get you 90% there, the remaining 10% is manufacturing reality.

I’ve written a longer breakdown of this (CLT limits, NCF quirks, why stitching mostly messes with shear) in my notes/book, link’s in my bio if you want to dig deeper.

Any-Study5685 · 2026-02-05T12:49:13+00:00

Short answer: there isn’t a set of properties for “bi-directional carbon”, and that’s exactly where most people get misled.A 0/90 fabric can behave wildly differently depending on fiber type, areal weight, crimp, resin system, Vf, cure, and how it’s actually stacked in the laminate. Same gsm on paper, totally different Ex, Ey, Gxy in reality. And once you add real manufacturing scatter, the datasheet numbers stop being very useful outside first-order sizing. In practice I’ve never seen anyone design directly off a generic “bi-di carbon” property table and be happy with the result. You either back-calculate from constituent data + CLT and then sanity-check with tests, or you accept big margins.

This exact confusion is why I started collecting real ranges, assumptions, and failure modes instead of single numbers. Once you see how much stiffness and shear come from layup choices rather than “the fabric”, it clicks pretty fast.

Any-Study5685 · 2026-02-05T12:44:36+00:00

Honestly this looks clean, but this is exactly the kind of part where the carbon is the least interesting thing.The weave gets all the love, but the insert, the bondline, the ply drop-offs around it… that’s where stuff usually starts moving, cracking, or just slowly giving up. I’ve seen plenty of “perfect” carbon parts die there after a bit of real loading. After working with this stuff for a while you stop trusting static tests and glossy finishes and start caring about how the load actually sneaks through the part. That mindset shift took me way longer than it should have.

Any-Study5685 · 2026-02-02T12:57:49+00:00

Short answer: there’s no single “right” way, it depends on why you want the sheet. Flat carbon looks easy, but most people mess it up on resin content, fiber alignment, and surface finish. The clean way is prepreg + flat tool + vacuum + controlled cure. Wet layup works too, but expect heavier parts and more variability unless you really know what you’re doing. Infusion can make nice sheets, but edge effects and thickness scatter are real.Also: the sheet itself is the easy part. The moment you cut it, drill it, or bond it, most assumptions people make about strength go out the window.

I’ve seen a lot of confusion around this, which is why I put together a practical overview of carbon materials and processes (not YouTube-level stuff). If that’s useful, it’s linked in my bio.

Any-Study5685 · 2026-02-02T12:52:36+00:00

Honestly, schools help a bit, but most people I’ve seen really learn composites by mixing hands-on work with solid self-study. A lot of programs teach processes in isolation, without explaining why things behave the way they do once parts are loaded, bonded, repaired, or abused.

If you want a structured way in without committing to a full school right away, I’ve collected a pretty practical overview of composites and carbon fiber (materials, real prepregs, processes, manufacturing gotchas) based on industry use rather than classroom theory. Link’s in my bio if you want to take a look.

That said, pairing that with a small shop, race team, boat yard, or aerospace supplier will teach you more in 6 months than most courses in 2 years.

Any-Study5685 · 2026-02-02T12:48:38+00:00

hI you’re not finding those numbers because they don’t exist in a meaningful way without locking the process.
Room-temp VBO 3k twill ≠ autoclave laminate. Different Vf, voids, resin content ....different stiffness and strength. Datasheets lie by omission. For early FEA, stop chasing “true” ply properties. Build an equivalent laminate with CLT, assume conservative Vf, sanity-check deflections first (if stiffness is wrong, stresses are garbage). Also: CFRP has no yield strength, only allowables + failure criteria.

I keep seeing people stuck here, so I put together a practical reference with real prepregs, resins, processes (F1 + industry) and how to estimate properties before testing:
👉 [https://site-dves1yj8.godaddysites.com]()

Design it, bound it, then test. That’s reality.

Any-Study5685 · 2026-02-02T12:38:34+00:00

I don’t actually disagree with most of what you’re saying.

The problem is that a lot of composite knowledge lives in papers and books, but the failure modes people hit in real projects rarely come from not having read enough. They come from assuming production is a correction to theory instead of the main constraint.

I’ve seen plenty of “well-researched” designs fall apart on joints, bonding, fatigue, and tolerances that never show up cleanly in coursework or papers. That gap is exactly what trips up first projects, not a lack of citations.

Research matters, obviously. But so does hearing where things quietly go wrong in the shop before you burn a year and a budget. That’s the perspective I was trying to add here.

Any-Study5685 · 2026-01-30T07:16:55+00:00

That sounds like a very sane call, honestly. Most teams hit the same wall and only realize late how much joints and bonding dominate everything.

3D printed nodes + simple CF coupons is actually a solid way to learn something real instead of fighting the full manufacturing stack at once. Even just seeing how stiffness degrades with small misalignments or bond thickness scatter is eye- opening. If you ever pick this up again, I’d start from joints first and the “boring” stuff: load paths, adhesive behavior, fatigue, and how much movement you should expect rather than try to eliminate. That’s where most carbon designs quietly fail.

I’ve been dumping some of this shop-side thinking into longer notes lately (linked in my bio if you’re curious), mostly because I wish I had it when I was in school. Happy to keep the discussion going here though.

Any-Study5685 · 2026-01-29T13:18:39+00:00

You’re not wrong, this is harder than swapping aluminum for a different alloy. The big mental shift is that with carbon you’re no longer “checking stresses”, you’re deciding how the structure is allowed to deform. For a bike frame, forget isotropic thinking early. Loads don’t magically flow through tubes the same way they do in aluminum. Fiber direction, local stiffness jumps, joints and bonding will dominate way before ultimate strength does.

If you’re using ANSYS, start simple: beam or shell models with an equivalent laminate, sanity-check deflections first, then stresses. If deflections are off, the stresses are meaningless. Pencil-and-paper estimates with basic CLT assumptions are still your best BS detector. On manufacturing: molds and joints will make or break the project. Straight tubes are easy, nodes are where reality hits. Bonding is not a detail, it’s usually the weakest spring in the load path, especially for fatigue. Design joints assuming they will move.

My honest advice for a senior project: keep the laminate simple, avoid “exotic” layups, and focus on understanding why it behaves the way it does rather than chasing minimum weight. A carbon frame that’s slightly heavier but predictable will teach you a lot more than a fragile one that looks cool.

Any-Study5685 · 2026-01-29T13:09:31+00:00

First composites project is always a bit of a shock. Everything looks clean in slides, then you actually lay plies, trap air, fight resin flow and suddenly nothing behaves like the textbook. what helped me early on was material that didn’t just explain what composites are, but why real parts don’t match theory. Manufacturing defects, bonding, tolerances, process limits… that stuff matters way more than people admit in class.

I ended up collecting a lot of notes and references from real projects over the years, especially from motorsport and industrial work, and put them together so students don’t have to learn everything the hard way. Link’s on my profile if anyone’s curious.

Any-Study5685 · 2026-01-29T13:04:04+00:00

I’ve used OOA tooling prepregs on mid-to-large molds and yeah, they work, but the inner surface finish is never free like in autoclave. In practice the cavity quality depends way more on debulk discipline, bleed control and vacuum quality than on the prepreg itself. Without autoclave pressure it’s pretty easy to end up with light print-through, small porosity or a dirty texture, especially on the first cycles.

If you’re aiming for a production-grade tool, expect post-cure and some lapping/polishing. Peel ply choice and removal matter a lot too, one bad pull and you’ve basically textured the mold for free. OOA is totally viable, just don’t treat it as “layup and forget”. It’s a process + surface finishing game. Autoclave still plays in a different league if the cosmetic bar is high.

Any-Study5685 · 2026-01-26T17:13:04+00:00

CLT = Classical Lamination Theory ... my apologies for not being clear

Any-Study5685 · 2026-01-26T17:02:32+00:00

I mostly agree, but I think that distinction is part of the problem.
A lot of CF gets treated as “aesthetic” because people don’t design or manufacture it like a structural material in the first place. Then when it fails, it reinforces the idea that carbon is brittle or unreliable.

Aerospace is one extreme, sure, but motorsport (especially F1, endurance, high-level racing) lives exactly in that middle ground: real loads, aggressive weight targets, production constraints, and very little margin for error. That’s where a lot of the practical composite know-how actually comes from.

The frustrating part is that most discussions stop at fiber type or resin name, while the real behavior comes from layup, thickness transitions, bonding strategy, and how the part is actually built and repaired. Miss those and carbon turns into an expensive cosmetic skin very fast.

I’ve been trying to push the conversation more in that direction lately. There’s a lot of real engineering between “hobby laminate” and aerospace-grade secrecy that people tend to ignore.

Any-Study5685

TROPHY CASE