Laravel - Array to string conversion

I am trying to show the related applications to abstract, I have used the code below but I am getting this error

Array to string conversion

My controller

public function show($A_ID){

  $abstract = Project::find($A_ID);

  // I believe the issue is caused by the line below but I am not sure what is wrong about it 

  $applications = Application::find($A_ID);
  return view('Abstracts.show')->with('abstract', $abstract)
                             ->with($applications);
}

My model

<?php

namespace App;
use Illuminate\Database\Eloquent\Model;
use Traits\HasCompositePrimaryKey; 

class Application extends Model{


    //Table name
    protected $table = 'student_application';

    //composite key
    protected $primaryKey = array('A_ID', 'S_ID');
    protected $fillable = ['S_Justification' ];
    public $incrementing = false;}

I want to note that the composite key is declared using this answer number two with currently 59 votes

For more information here is my view

@if (count($applications)>0)
@foreach ($applications as $application)
<tr>
        <td><h5></h5></td>
</tr>
@endforeach
@else 
<p> This project has no applications </p>
@endif

via Chebli Mohamed