Mistras Group holder reports 17.4% stake

An individual and related grantor retained annuity trust disclose beneficial ownership of about 17.4% of Mistras Group’s common stock.

Rhea-AI Filing Summary

Mistras Group, Inc. (MG) has a significant shareholder group reporting a 17.4% stake in its common stock. Stephanie Athena Foglia and the 2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos, acting as joint reporting persons, together beneficially own 5,532,313 shares of Mistras common stock. These ownership percentages are based on 31,849,893 shares outstanding as of August 10, 2026, as reported by the company.

Foglia has sole voting and dispositive power over 1,608,595 shares and shared voting and dispositive power over 3,923,718 shares held through the trust. The shares are held for investment purposes. The reporting persons state they currently have no specific plans for corporate actions but may buy or sell additional shares or consider proposals regarding Mistras in the future.

Key Figures

Beneficial ownership (all reporting persons): 5,532,313 shares Ownership percentage (all reporting persons): 17.4% Trust beneficial ownership: 3,923,718 shares +5 more

8 metrics

Beneficial ownership (all reporting persons) 5,532,313 shares Total Mistras Group common shares beneficially owned, representing approximately 17.4% of the class

Ownership percentage (all reporting persons) 17.4% Portion of Mistras Group common stock beneficially owned by the reporting persons

Trust beneficial ownership 3,923,718 shares Mistras Group common shares beneficially owned by the 2025 Irrevocable Two-Year Grantor Retained Annuity Trust

Trust ownership percentage 12.3% Portion of Mistras Group common stock beneficially owned by the trust alone

Shares outstanding baseline 31,849,893 shares Mistras Group common shares outstanding as of August 10, 2026, used for percentage calculations

Foglia sole voting and dispositive power 1,608,595 shares Shares over which Stephanie Foglia reports sole voting and dispositive power

Shared voting and dispositive power 3,923,718 shares Shares over which Foglia and the trust report shared voting and dispositive power

Trust gift acquisition 4,722,686 shares Shares of Mistras Group common stock acquired by the trust via gift from Aspasia F. Vahaviolos on December 31, 2025

Key Terms

beneficially owned, Grantor Retained Annuity Trust, dispositive power, sole voting power, +2 more

6 terms

beneficially owned financial

"The total number of shares which are beneficially owned by the Reporting Persons is 5,532,313 shares"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Grantor Retained Annuity Trust financial

"2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos"

A grantor retained annuity trust (GRAT) is an estate-planning tool where the person who creates the trust transfers assets into it but receives fixed cash payments (an annuity) from the trust for a set number of years; whatever remains after that term passes to designated beneficiaries. It matters to investors because it can shift future appreciation of assets out of the creator’s taxable estate—like putting an asset into a timed vending machine that pays you fixed amounts while any extra value that grows inside the machine goes to heirs with reduced gift or estate tax consequences.

dispositive power financial

"Sole Dispositive Power 1,608,595.00 Shared Dispositive Power 3,923,718.00"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

sole voting power financial

"Sole Voting Power 1,608,595.00 Shared Voting Power 3,923,718.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

Schedule 13D regulatory

"previously filed a statement on Schedule 13G to report the acquisition"

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

joint filing agreement regulatory

"being filed pursuant to a joint filing agreement filed as Exhibit 1.1"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How much of Mistras Group, Inc. (MG) do the reporting persons say they own?

They report beneficial ownership of 5,532,313 shares of Mistras Group common stock, representing approximately 17.4% of the outstanding shares, based on 31,849,893 shares outstanding as of August 10, 2026, as reported by the company.

Who are the reporting persons in this Schedule 13D/A for MG?

The reporting persons are Stephanie Athena Foglia and the 2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos. Foglia serves as trustee of the trust and is Director of Total Rewards at Mistras Group.

What percentage of Mistras Group (MG) shares does the trust alone beneficially own?

The 2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos reports beneficial ownership of 3,923,718 shares of Mistras Group common stock, representing approximately 12.3% of the outstanding shares.

How are voting and dispositive powers over MG shares allocated for the reporting persons?

Stephanie Foglia has sole voting and dispositive power over 1,608,595 shares and shared voting and dispositive power over 3,923,718 shares held through the trust. The trust itself reports shared voting and dispositive power over 3,923,718 shares and no sole power.

What is the stated purpose of the Mistras Group (MG) share holdings by the reporting persons?

The reporting persons state they hold Mistras Group common stock for investment purposes. They currently report no specific plans for corporate actions but reserve the right to acquire or dispose of shares or consider proposals regarding the company.

How and when were a large portion of the MG shares in the trust acquired?

The trust was established on December 31, 2025, and 4,722,686 shares of Mistras Group common stock held by the trust were acquired that same day by gift from Aspasia F. Vahaviolos, the grantor of the trust.

What MG shares does Stephanie Foglia directly own outside the trust?

Stephanie Foglia directly owns 2,000 shares purchased for cash in Mistras Group’s initial public offering and 12,663 shares received as employment compensation. All other shares she beneficially owns are held indirectly through immediate family members or the trust.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/14/2026 - 09:29 PM Accepted by SEC EDGAR 09/14/2026 - 09:28 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 3)

Mistras Group, Inc.

(Name of Issuer)

Common Stock, $0.01 par value

(Title of Class of Securities)

(CUSIP Number)

Stephanie Foglia
504 Hiram Road,
Plymouth Meeting, PA, 19462
610-324-6463

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

09/10/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP No.

1

Name of reporting person

Stephanie Athena Foglia

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 1,608,595.00
8	Shared Voting Power 3,923,718.00
9	Sole Dispositive Power 1,608,595.00
10	Shared Dispositive Power 3,923,718.00

11

Aggregate amount beneficially owned by each reporting person

5,532,313.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

17.4 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No.

1

Name of reporting person

2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,923,718.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,923,718.00

11

Aggregate amount beneficially owned by each reporting person

3,923,718.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.3 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.01 par value
(b)	Name of Issuer: Mistras Group, Inc.
(c)	Address of Issuer's Principal Executive Offices: 195 Clarksville Road, Princeton Junction, NEW JERSEY , 08550.
Item 1 Comment: The percentage calculations reflected in Rows (13) above are based on 31,849,893 outstanding shares as of August 10, 2026, as reported by the issuer.
Item 2.	Identity and Background
(a)	This Schedule 13D is being filed pursuant to a joint filing agreement filed as Exhibit 1.1 hereto by and between (i) Stephanie Foglia and (ii) the 2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos (the "Trust"). Ms. Foglia and the Trust are referred to herein collectively as the "Reporting Persons."
(b)	The business address of each of the Reporting Persons is c/o the Issuer, 195 Clarksville Road, Princeton Junction, New Jersey 08550
(c)	Stephanie Foglia is the Director of Total Rewards for the Issuer.
(d)	None of the Reporting Persons has been convicted in a criminal proceeding during the last five years.
(e)	None of the Reporting Persons has been party to any civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree, or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws, or finding any violation with respect to such laws during the last five years.
(f)	Ms. Foglia is a citizen of the United States of America.
Item 3.	Source and Amount of Funds or Other Consideration
	The Trust was established by its grantor, Aspasia F. Vahaviolos. The shares held by the Trust were acquired by a gift from Ms. Vahaviolos. Ms. Foglia is the trustee for the trust. Ms. Foglia directly owns 2,000 shares purchased for cash in the issuer's initial public offering and holds 12,663 shares received as compensation for employment with the issuer. All other shares beneficially owned by Ms. Foglia are indirectly held through immediate family members.
Item 4.	Purpose of Transaction
	The Reporting Persons acquired, and presently beneficially own, shares of the issuer's common stock for investment purposes. None of the Reporting Persons currently has any plans or proposals that would result in or relate to any of the transactions or changes listed in Items 4(a) through 4(j) of Schedule 13D. However, as part of their ongoing evaluation of their investment and investment alternatives, the Reporting Persons may consider such matters and, subject to applicable law, may formulate a plan with respect to such matters or make formal proposals to the board of directors of the issuer, other stockholders of the issuer, or other third parties regarding such matters. The Reporting Persons reserve the right to acquire additional securities of the issuer in the open markets, in privately negotiated transactions (which may be with the issuer or with third parties) or otherwise, to dispose of all or a portion of their holdings of securities of the issuer, or to change their intention with respect to any or all of the matters referred to in this Item 4.
Item 5.	Interest in Securities of the Issuer
(a)	The responses to Rows 11 and 13 in each Reporting Person's cover page, indicating the aggregate number and percentage of shares of the issuer's common stock beneficially owned by each Reporting Person, are incorporated herein by reference. The total number of shares which are beneficially owned by the Reporting Persons is 5,532,313 shares, or approximately 17.4% of the outstanding shares of the issuer's common stock. The ownership percentages were calculated based on 31,849,893 outstanding shares as of August 10, 2026, as reported by the issuer.
(b)	The responses of each Reporting Person to Rows 7 through 10 on the cover page of this Schedule 13D are incorporated herein by reference.
(c)	The Trust was established on December 31, 2025, and 4,722,686 shares of the issuer held by the Trust Were acquired by a gift from Ms. Vahaviolos on the same date.
(d)	Other than as described herein, no other person is known to have the right to receive and the power to direct the receipt of dividends from, or the proceeds from the sale of, such common stock beneficially owned by the Reporting Persons.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	None.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 1.1 - Joint Filing Agreement of the Reporting Persons (previously filed as Exhibit 1.1 to the Schedule 13D filed with the Securities and Exchange Commission on March 31, 2026 (File No. 005-85079)).

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Stephanie Athena Foglia

Signature:	/s/ Stephanie Foglia
Name/Title:	Stephanie Foglia
Date:	09/14/2026

2025 Irrevocable Two-Year Grantor Retained Annuity Trust of Aspasia F. Vahaviolos

Signature:	/s/ Stephanie Foglia
Name/Title:	Stephanie Foglia/Trustee
Date:	09/14/2026