Modular JavaEE projects

I am starting currently with a project, which should be build up with modular components. I have one core project containing some JAX-RS Webservice classes, some entity beans and core business logic.

Module A will now extend the core module by its behavior (new Webservice classes, new entity beans referencing the core entities) Module B ... and so on

Is it possible to create single projects for every module, containing EntityBeans and Webservice classes and combining them in one ear to work interoperable at the end?

My problem is that I am stuck on integrating Module A together with the core module in one ear, because the PersistenceUnit cannot be started correctly.

Following pom-Files are showing my current setup: Core-Project:

<project xmlns="http://ift.tt/IH78KX" xmlns:xsi="http://ift.tt/ra1lAU" xsi:schemaLocation="http://ift.tt/IH78KX http://ift.tt/VE5zRx">
    <modelVersion>4.0.0</modelVersion>
    <groupId>...</groupId>
    <artifactId>core</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>ejb</packaging>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <failOnMissingWebXml>false</failOnMissingWebXml>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
 ....
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-ejb-plugin</artifactId>
                <version>2.5</version>
                <configuration>
                    <ejbVersion>3.1</ejbVersion>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Module A:

<project xmlns="http://ift.tt/IH78KX" xmlns:xsi="http://ift.tt/ra1lAU" xsi:schemaLocation="http://ift.tt/IH78KX http://ift.tt/VE5zRx">
    <modelVersion>4.0.0</modelVersion>
    <groupId>...</groupId>
    <artifactId>moduleA</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>ejb</packaging>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>...</groupId>
            <artifactId>core</artifactId>
            <version>${project.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
           <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-ejb-plugin</artifactId>
                <version>2.5</version>
                <configuration>
                    <ejbVersion>3.1</ejbVersion>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

and the ear-pom:

<project xmlns="http://ift.tt/IH78KX" xmlns:xsi="http://ift.tt/ra1lAU" xsi:schemaLocation="http://ift.tt/IH78KX http://ift.tt/VE5zRx">
    <modelVersion>4.0.0</modelVersion>
    <groupId>...</groupId>
    <artifactId>releng</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>ear</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>...<groupId>
            <artifactId>core</artifactId>
            <version>${project.version}</version>
            <type>ejb</type>
        </dependency>
        <dependency>
            <groupId>...</groupId>
            <artifactId>moduleA</artifactId>
            <version>${project.version}</version>
            <type>ejb</type>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-ear-plugin</artifactId>
                <version>2.10</version>
                <configuration>
                    <version>7</version>
                    <defaultLibBundleDir>lib</defaultLibBundleDir>
                    <finalName>app</finalName>
                    <fileNameMapping>no-version</fileNameMapping>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Or is my approach complete nonsens? Then please give some hints how to setup a modular project ;)