Order complete emails are sent to the customer when the order is marked complete and usual indicates that the order has been shipped.
Author: WooThemes
Inheritance: extends WC_Email
 /**
  * get_heading function.
  *
  * @access public
  * @return string
  */
 function get_heading()
 {
     return apply_filters('woocommerce_email_heading_customer_renewal_order', parent::get_heading(), $this->object);
 }
    public static function view_completed_email($order)
    {
        $email_exchanger = new WC_Emails();
        $email = new WC_Email_Customer_Completed_Order();
        $email->object = $order;
        ?>
<html>
			<head>
				<title><?php 
        echo $email->get_subject() . ' - ';
        _e('Preview', 'opentickets-community-edition');
        echo ' - ' . get_bloginfo('name');
        ?>
</title>
			</head>
			<body>
				<?php 
        echo $email->get_content();
        ?>
			</body>
		</html><?php 
        exit;
    }