Dear Reader,

I hope you are doing well. I just wanted to write quickly and briefly about some of my recent reflections. In today's newsletter, I will focus on:

1. Technical Reflections: The usefulness of PBCs for Failure Envelops
2. Behind the Scenes at CM Videos: Update on YouTube Channel
3. Quote for the week: When should you get started

Let us get into it

Technical Reflection

Failure Envelops and Periodic Boundary Conditions

One of the thing we do a lot when working with composite materials is to generate a failure envelop. It is important because most composites are brittle and show quite linear behaviour, small plasticity, and then brittle failure. So, in order to identify regions of practical uses of composites, the failure envelop is important. It establishes the bounds within which the material is useful for design purposes. Beyond the failure envelop, then eventual failure takes over and then material because inadmissible for design.

Therefore, understanding this bound (i.e. the failure envelop) is critical for such quasi-brittle materials as composites. The interesting thing about failure envelop is that it is often defined by the interaction of two or more stress histories. One typical and quite commonly plotted failure envelop is that where a uniaxial load (say stress in xx-axis) is combined with a shear load (stress on xy-plane). An envelop is therefore generated. Typical example is given below for such an envelop.

I got an email this week from a viewer of the YouTube channel with this question:

On reading that email, I remembered that I did make a video about failure envelops and Periodic Boundary Conditions awhile back. I will post that video here for you to review.

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In principle, here are my answers:

1. It is possible to use PBCs to extract failure envelops.
2. Provided you have a clear way of imposing the combined loads, and subsequently extracting model variables (displacements and stress), then you could easily do this.
3. You have to be careful though with laminates as they are typically modelled using shell elements so how you handle the homogenization (based on post-PBC application) is somehting to watch out for.

If you watch the video above, you would get some seed ideas to help you develop a solution for your, as you work on failure envelops.

Behind the Scenes at CMVideos

Update on YouTube Channel

I have not been posting lately a lot on the YouTube channel. Some of you that have been visting the channel would realize that my last long-form video there was the video published in 2nd February 2025, about DeepSeek.

In lieu of videos (long form content), I have also been publishing shorts (extracted from my long form content). Again, the last post was on 9th March 2025.

I wanted to let you know that there is no need to be concerned about this. I have been going through a busy period at work and have struggled to find the time to make these videos.

The plan is that as the academic year in my university comes to an end, sometime late May 2025, I will be able to have more times to make videos.

I have also a plan to launch my first live cohort product and have a waiting list for it, which you can join by clicking the link below. The zeal is not going down at all with the YouTube channel and making contents for my audience, so please just bear with me during this period of limited video postings. I will continue to engage with you through other means.

Quote for the Week

When should you get started?

There is often a lot of challenges to get started when we intend to work on projects. Some persons like to do extensive research and this can be taking forever without any action being taken.

I recall when I was doing my PhD, I kept reading literature upon literature, and never felt I was ready to start writing my Transfer thesis (a thesis submitted within the first 1 year of PhD study) as part of a viva for transfer from MPhil to full PhD status.

At a certain point, my supervisor advised me that I should start writing and that how many papers I studied will not get me the transfer. It is what I actually wrote down that will lead to my successfully passing the viva.

I tell this story because my quote for this week is taken from Austen Kleon's book - Steal like an Artist. In the blurb of the book, I saw this quote:

Waiting until you know who you are - and all the facts about a matter before taking action will often cause you to take no action. We are generally wired to want to know more and there is this thing called the curse of knowledge. It means we know so much that we become unaware of the impact of our knowledge and we cannot effectively communicate to the audience what we know.

I will urge you, start before you feel ready. If there is a project you want to embark on, get started with it. You learn a lot from failure than from inaction. We are wired on a feedback system where we are continuously optimizing our approach to things based on how much feedback we have. It is part of our evolutionary reflex. If you never do a thing, you have no way of feeding this evolutionary feedback loop and so never benefit from optimizations we need in order to continue to be successful.