Add the below file to yourtheme/woocommerce/single-product/tabs/tabs.php. This will update the tabs to be an accordion. Update as required.

tabs.php

<?php
/**
 * Single Product tabs
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/single-product/tabs/tabs.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see 	https://docs.woocommerce.com/document/template-structure/
 * @author  WooThemes
 * @package WooCommerce/Templates
 * @version 2.4.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Filter tabs and allow third parties to add their own.
 *
 * Each tab is an array containing title, callback and priority.
 * @see woocommerce_default_product_tabs()
 */
$tabs = apply_filters( 'woocommerce_product_tabs', array() );

if ( ! empty( $tabs ) ) : ?>

	<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true"">
		<div class="panel panel-default">
			<?php $i = 0; foreach ( $tabs as $key => $tab ) : ?>
				<div class="panel-heading" role="tab" id="heading-<?php echo $i; ?>">
      				<h4 class="panel-title">
						<a role="button" data-toggle="collapse" data-parent="#accordion" href="#collapse-<?php echo $i; ?>">
							<?php echo apply_filters( 'woocommerce_product_' . $key . '_tab_title', esc_html( $tab['title'] ), $key ); ?>
						</a>
					</h4>
    			</div>

			<div id="collapse-<?php echo $i; ?>" class="panel-collapse collapse <?php if ( $i == 0 ): echo 'in'; endif; ?>" role="tabpanel" aria-labelledby="headingOne">
      			<div class="panel-body">
					<?php if ( isset( $tab['callback'] ) ) { call_user_func( $tab['callback'], $key, $tab ); } ?>
				</div>
			</div>
		<?php $i++; endforeach; ?>
	    </div>
	</div>

<?php endif; ?>