If you're reading research papers now and then (or frequently, of course), you will probably have stumbled across The Paywall more often than you'd like. Murphy's rules for reading scholarly work definitely includes one that says "The article that sounds most interesting will be inaccessible due to some reason, preferably a paywall."

So. You'd like to read something, but the publisher would like to have half an arm, or maybe quarter of a leg for access to the volume, issue, or article? There's a few ways to get the article of interest without paying yourself. If you have a library card for a Uni library (you usually can get those without much fuss for the country you live in), and the library is within reach and has online access to the journal (which you can usually find out via their database) - there you go, you can access and download the article from a library computer. Bring your own USB stick, or mail it to yourself.

If that's not the case, there's networks like academia.edu and researchgate.net. Both are free to join, and they offer the possibility to network with researchers, follow them (so you get to see if they add something new) and read their papers. Authors upload pdf copies of their work; it's still legal, as the copies are not freely available, but within a closed group. You can also request a paper if it's not uploaded yet, and hope the person in question isn't as slow as I am with adding new things.

unpaywall.org is a database with free versions of paywalled articles. There are several ways to use the database for your research, such as integration in Zotero, but the easiest one I have found is to use Chrome with the unpaywall extension. When you are on a page with a doi, you can then hopefully see a green open padlock on the right side of your screen - click that, and you are taken to the place with the free version of the article. 

The Directory of Open Access Journals is just what the name implies - you can search for both journals and indexed articles. There is limited content available regarding medieval textiles, but there is some, from journals in a number of languages.

If you register at JSTOR, you can read a certain number of articles online for free each month. 

Then, of course, there's a lot of things that are available for free on the internet today. Here's my list of books, articles, and some article or publication databases:

The Virtual Library for Art, arthistoricum.net, has a full-text server called ART-Dok, made available by Heidelberg University Library. It offers members of the academic community worldwide the opportunity to publish their texts in electronic format on the internet at no charge. As for now, it provides free full-text access to 4,194 publications. You can also do fulltext searches through the texts. 

Several of the books written by Jutta Zander-Seidel, among them "Textiler Hausrat", are available for free at ART-Dok.

The Bryggen Papers are available for free, online, as pdf files. These volumes include the one about textile equipment and its working environment.  Bryggen Papers Archives

 The Metropolitan Museum also has an extensive list of publications that are available online and for free, and you can find those here.

The Open Access books available at OApen.org include Karina Grömer's book about prehistoric textiles, both in the German and the English version. You can find them here.

You can download the pdf version of Textile Terminologies from the Orient to the Mediterranean and Europe, 1000 BC to 1000 AD here.

The Journal for Archaeology in the Low Countries was only short-lived, but is open access. Vol. 2, published in 2010, includes an article by Chrystel Brandenburgh about early medieval textile remains.

The Archaeological Textiles Newsletter (now the Archaeological Textiles Review) has been around for quite a while, and they have published a lot of very interesting articles, most of them short but informative. You can download the issues from their website, for free. If you can, do consider subscribing to the Newsletter to support their work.

The Estonian find of the craft box from Lõhavere, which comes from the hillfort of the same name, dated to the 12th and early 13th century, is published in a little book, and that, too, is available online free of charge. The craft box, made from birch bark, contained textile remains, prefabricated and half-finished products, bronze ornaments and tools, some of them neatly stored in smaller boxes or little pouches. 

You can find the Birka publications here, and if you have a bit of time, also check out their English homepage.

York Archaeological Trust has been publishing a lot of books about various aspects and find groups of all the digs done there. York also boasts a number of textile finds and textile tool finds. The volumes 17/5 Textile, Raw Fibre and Cordage from Coppergate 16-22 and 17/11 Textile Production at 16-22 Coppergate are available as free pdf downloads from their site. (Direct links to the pdfs - but do visit their page listing the rest of the volumes of Archaeology of York, there's many more.) 

The list of publications by the Council of British Archaeology also includes the York volumes, but in addition it offers a number of research reports online for free download, on a variety of topics. You find the list here.

Lise Raeder Knudsen has a pdf book about Gotlandish Tablet Weaves on her website, free to download. It's in Swedish, with a very short English summary, but might still be interesting to you for the (slightly grainy, black-and-white) pictures of the originals. You might also want to check out her other publications in the list, which are partly available to download.

The Reallexikon zur Deutschen Kunstgeschichte is available online, for free, under the title of RDK Labor. It works like a wiki in that you can also submit articles, and it's a huge resource of information on German art history.

If you read German, you might also enjoy the Archive of the Zeitschrift für Lübeckische Geschichte.

DiVA portal is short for Digital Vetenskapliga Arkivet, a Scandinavian site where you can search for theses and papers from 49 university and research institutions.

The University Publisher of Kassel University offers books (dissertations, but other types as well) both as printed volumes and as pdf downloads, the latter being entirely free. You can see the whole programme of the publisher here.

The Centre for Textile Research in Denmark ran the project "Margrethe Hald Archive", and part of this was the digitisation of several of her works. These are free to download, find the links to the pdf files here.

The complete archive of the LMBRIC (Loop Manipulation and Braiding Research and Information Center) by Masako Kinoshita is available here.